INSENSITIVITY TO SUFFERING: THE RELATION OF PSYCHOPATHIC TRAITS TO SOMATIC PROCESSING, FIRST-PERSON AND THIRD-PERSON PAIN by Kimberley Kaseweter B.Sc., University of Northern British Columbia. 2011 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN PSYCHOLOGY UNIVERSITY OF NORTHERN BRITISH COLUMBIA April 2015 © Kimberley Kaseweter, 2015 UMI Number: 1526501 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Di!ss0?t&iori Publishing UMI 1526501 Published by ProQuest LLC 2015. Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 Abstract Despite a growing body of evidence indicating that psychopathy entails profound deficits in emotional processing, the particular dysfunction in pain perception remains poorly understood. This study examined the influence of psychopathic traits on first-person and third-person pain perception. Undergraduate students (N = 110) completed measures of psychopathic traits and empathy. Participants then underwent a cold-pressor task during which they rated their pain experience and physiological activity was recorded. Next, participants watched a video of 60 clips of other people experiencing pain. Following each clip, participants rated the perceived level of pain. Higher levels of psychopathic traits were related to a lower pain tolerance, but not to differences in pain ratings or physiological activity. However, psychopathic traits were associated with a mismatch between individuals’ subjective ratings and physiological activity. Lastly, psychopathic traits were associated with decreased sensitivity to others’ pain. These findings provide novel insights into the emotional deficit characterizing psychopathy. Table of Contents Abstract ii Table of Contents iii List of Tables v List of Figures vi Acknowledgement vii Introduction 1 History and Classification of Psychopathy 4 Affective Deficit 7 Emotion recognition in others. 8 Emotion recognition in self. 10 Theoretical Models of Psychopathy 11 Research Question 14 Methods 18 Participant Sampling and Characteristics 18 Apparatus and Materials 18 Self-report measures. 19 Assessment o f first-person pain. 20 Assessment o f third-person pain. 24 Procedure 26 First-person pain perception. 26 Third-person pain perception. 28 Data Reduction and Statistical Analysis 28 First-person pain perception. 28 Third-person pain perception. 30 Missing Data and Outliers Results 32 33 Personality Variables 33 First-Person Pain Perception 35 Pain tolerance. 37 iii Pain ratings. 37 Psychophysiological data. 38 Third-Person Pain Perception 41 Discussion 48 Overview o f Results 48 First-Person Pain Perception 49 Implications. Third-Person Pain Perception Implications. 57 59 61 Practical Applications 63 Identification. 63 Treatment. 65 Future Directions 66 Strengths and Limitations 67 Conclusion 69 References 70 Appendix A 81 Demographics Questionnaire Appendix B 81 82 Self-Report Psychopathy Scale III 82 Norms for offender, student, and community samples 84 Appendix C Toronto Empathy Questionnaire Appendix D 85 85 86 Task Instructions 86 First-Person Pain Task 86 Third-Person Pain Task 87 iv List of Tables Table 1. Descriptive Information From the SRP-III and TEQ 33 Table 2. Means and Standard Deviations for the SRP-III for Males and Females 34 Table 3. Pearson Correlations between Personality Variables 35 Table 4. Descriptive Information From the Cold-Pressor Task. 36 Table 5. Pearson r Correlations Between Responses During the Cold-Pressor and SRP-III Scores. 38 Table 6. Pearson r Correlations Between Psychophysiological Variables and Personality Characteristics 40 Table 7. Descriptive Information for Discrimination and Response Bias Scores 42 Table 8. Pearson r Correlations Between Response Bias and Personality Characteristics 45 Table 9. Pearson r Correlations Between Discriminability and Personality Characteristics 46 v List of Figures Figure 1. Mean intensity and unpleasantness ratings across all time points in coldpressor task. 36 Figure 2. ROC Plot o f Participants’ Average Performance for Third-Person Pain Perception 44 Figure 3. ROC Plot o f Participants Scoring High and Low in Psychopathy at No Versus Moderate Pain 47 Figure 4. Mean intensity rating across time during the cold-pressor. Low and High SRP-III scores were determined using a median split. 52 vi Acknowledgement This thesis would not have been possible without the support of many people. First, I would like to express my deepest appreciation to my supervisor, Dr. Ken Prkachin, for the invaluable support, encouragement, and guidance he has provided me over the last few years. I would also like to thank the other members of my committee, Dr. Glenda Prkachin and Dr. Peter MacMillan, for their knowledge and advice throughout this process. Thanks also to Erin Browne for her assistance and insight; to Michael Moffat, Jasprit Nijjar, Stephanie Pusch, and Jessica Duris for their generous volunteer work; and to my friends and family for their encouragement. Lastly, thank you to the Social Sciences and Humanities Research Council (SSHRC) and University of Northern British Columbia (UNBC) for funding this research. INSENSITIVITY TO SUFFERING: THE RELATION OF PSYCHOTHIC TRAITS TO SOMATIC PROCESSING, FIRST-PERSON AND THIRD-PERSON PAIN “It is not against reason to prefer the destruction of half the world to the scratching o f my finger” (David Hume, A treatise on human nature. 1789) Introduction The foregoing quotation captures one of the ways in which Scottish Enlightenment philosopher, David Hume, framed the importance of “moral sentiments”— those elements of human experience that, among other things, involve our ability to sense and respond to the needs of others and to balance self-interest against the interests of others. Most people achieve such a balance upon which, arguably, harmonious functioning o f societies is dependent. But the quotation also can be used to recognize another social reality, which is that some people do appear to be indifferent to the suffering of others, suffering that they often inflict themselves. Whether those same people are sensitive or indifferent to their own personal suffering is a question of some importance because it may provide insight into the broader question of why they may be insensitive to the suffering o f others. Many people engage in acts that deliberately, or by omission, cause others to suffer. Sometimes the motivations for such acts, which can range from emotional neglect or abuse through material crimes to capital offences, are apparent—being overcome by some emotion or pursuing personal gain. Occasionally, they appear “cold-blooded” and arise, in part, out of indifference. The people who perform such acts are sometimes psychopaths. Psychopathy is a severe and chronic personality disorder that is characterized by a vast array o f affective and interpersonal deficiencies, as well as impulsive antisocial behavioural tendencies (Cleckley, 1976). Specifically, psychopathic characteristics have been said to include a lack of empathy, lack of guilt, callousness, glibness, low tolerance for 1 frustration or aggression, impulsivity, irresponsibility, and manipulation of others (Hare 2003; Viding, 2004). Additionally, psychopathic traits have been associated with increased criminality, increased rates of violent behaviour, suicide attempts, and homelessness (Coid, Yang, Ullrich, Roberts & Hare, 2009; Leistico, Salekin, DeCoster & Rogers, 2008). Although psychopaths represent only 1% of the general population and approximately 25% of prison populations (Babiak & Hare, 2006; Hare, 2003), they have been estimated to commit as much as 30-50% of all violent crimes and are five times more likely than nonpsychopathic offenders to recidivate violently (Serin & Amos, 1995). Psychopathy also is associated with more severe forms of sexual violence (e.g., Hare, Cooke, & Hart, 1999; Serin, Mailloux, & Malcolm, 2001). It has been estimated that psychopathy alone costs the US criminal justice system $460 billion per year (Kiehl & Hoffman, 2011). These numbers do not include the costs of the overrepresentation of psychopaths in psychiatric hospitals, or indirect costs o f their crimes such as treatment for victims. Thus, it is clear that psychopathy has considerable social, economic, and emotional costs for individuals and society. For these reasons, there is a pressing need for the identification and treatment of psychopathy. As such, a considerable amount of research on psychopathy has been conducted, generating numerous theories of the disorder. Based on this research, it is evident that psychopathy is associated with a profound emotional deficit that is believed to contribute to the high rates o f antisocial behaviour with which it is associated. However, the details of these emotional deficits are unclear and the evidence that exists is weak and often contradictory. For example, although it has been consistently shown that psychopathic individuals lack empathy, which could conceivably contribute to their high rates of crime, the mechanisms underlying this problem have remained unclear. 2 A recent revivification of interest in empathy has led to novel insights as to its nature and determinants, with implications for understanding the affective processes linked with psychopathy. Goubert, Craig, Vervoort, Morley, Sullivan et al (2005, p. 285) have defined empathy as “ ...a sense of knowing the experience of another person.” Based on neuropsychological and neuroimaging studies, Decety, Jackson and Brunet (2007) have proposed a model of empathy that identifies three core features that are nominally independent, but interact to determine a person’s response to another person’s experiences. It includes a sensory or emotional sharing component that involves personal representation of others’ experiences— a kind of intersubjective resonance. It also includes processes that contribute to mental flexibility, including the ability to separate oneself from but take the perspective of the other person and executive processes that allow one to control one’s own emotional reactions. These components are, in turn, influenced by an individual’s selfawareness, including one’s ability to perceive personal affective experiences. Any affectively provocative experience can elicit empathic processes in others, but we commonly think o f empathy as occurring when something distressing happens to another. A prototypic scenario relevant to empathy occurs when pain is inflicted on someone else. A considerable amount o f recent empathy research has involved studies of the response to pain in others (see Prkachin, Kaseweter & Browne, in press, for a review). Studies of pain have the advantage o f enabling investigation of a range of personal and interpersonal variables relevant to empathy in an ecologically valid manner. The study o f responses to pain seems particularly relevant to unravelling the problem of psychopathy, since disturbances in pain perception are frequently invoked as explanations for psychopathic deficits and since infliction of pain (physical or emotional) on others is a common feature of the life histories of 3 people described as psychopathic. If, as is strongly implied in the literature, psychopathic individuals have a deficit in empathy and if the Decety et al (2007) and similar models are correct in suggesting that empathy involves partially independent but interacting components, the question arises as to where any psychopathic deficit might be located. Do psychopaths lack empathy for others’ pain because they do not feel pain, do not see pain, or simply do not care? Without a sufficient understanding of these emotional processing deficits, treatment o f psychopathy and its associated risk factors or devising public policy to address the issue would be difficult. Indeed, numerous theorists, researchers, and clinicians have come to the conclusion that psychopathy is difficult, if not impossible, to treat (Cleckley, 1941; Hare, 1991). For this reason, it has been suggested that the etiological theories o f psychopathy require refinement (Salekin, 2002). That is, before an effective treatment programs for or adequate preventive or societal response to psychopathy can occur, it is first necessary to better understand the specific causes o f the disorder (Salekin, 2002). History and Classification of Psychopathy The French physician Phillipe Pinel (1745-1826) is generally credited with recognizing psychopathy as a distinct mental disorder (Smith, 1978). In 1806, he was among the first to describe psychopathic individuals when he wrote about patients suffering from manie sans delire, meaning they were “insane” but “without delirium.” Pinel characterized these patients as individuals having a lack of restraint, and whose behaviour was marked by utter remorselessness for their actions (Hare, 1993). In 1941, with the publication of The Mask o f Sanity, Cleckley provided extensive clinical descriptions of the characteristics of psychopathy, which have remained relatively stable to the present day (Hart & Hare, 1997; Salekin, 2002). Although the personality characteristics of psychopathy put forward by 4 Cleckley, such as a lack of remorse, impulsivity and callousness, were included in the original Diagnostic and Statistical Manual of Mental Disorders (DSM; American Psychiatric Association, 1952), subsequent editions consisted largely of behavioural descriptions focusing on social deviance and criminality under the term Antisocial Personality Disorder (APD; Arrigo & Shipley, 2001; Millon, 1981). This shift from personality-based descriptions of psychopathy to behaviourally-based descriptions occurred because of the prevailing belief among members of the DSM-III Task Force that the clinical inferences required to determine the personality characteristics o f a psychopath lowered the reliability of accurate diagnosis (Arrigo & Shipley, 2001; Hare 1996). Although the behavioural focus increased the diagnostic reliability of APD, it decreased the validity. The category has been said to be so broad that it might include people who have performed almost every known criminal offense (Flint-Stevens, 1993; Hare, Hart & Harpur 1991). For example, Gacono and Hutton (1994) stated “Sixty to seventy-five percent of any prison population in the USA could be expected to meet the criteria for APD, while slightly less than one-fourth would be considered psychopathic by traditional definition.” Paradoxically, the APD category has also been said to be too narrow in that it excludes individuals who meet the personality characteristics of a psychopath but lack the criminal/antisocial element (Millon, 1981). Thus, a distinction is typically made between psychopathy and APD (Frick, 1998; Hare & Hart, 1993). In order to address these criticisms o f the DSM and create a reliable and valid way to assess psychopathy, Hare developed the Psychopathy Checklist (PCL, 1980), followed by a revised version (Psychopathy Checklist-Revised; 1991). The PCL-R is capable of indexing not only the extreme antisocial behaviour seen in psychopaths, but also the personality 5 markers that lie at the core o f the disorder. The PCL-R is a 20-item clinical rating scale completed on the basis o f a semi-structured interview and detailed collateral information (file review). Each item of the scale is scored on a three-point scale from 0 (item does not apply) to 2 (item applies), resulting in a total score ranging from 0 to 40. Although the total score is dimensional, a cut-off score of 30 can be used to provide a categorical diagnosis of psychopathy. The PCL-R has been found to be a reliable and valid measure for the assessment o f psychopathy in criminal populations (Hare, Harpur, Hakstian, Forth, Hart, & Newman, 1990) and is generally considered to be the current “gold standard” for the assessment of psychopathy worldwide (e.g., Lynam, Hoyle & Neuman, 2006; Morana, Arboleda-Florez & Camara, 2005) Psychopathy, as measured by the PCL-R, was originally believed to be composed of two factors. Factor 1 was said to measure the affective and interpersonal features of psychopathy, such as egocentricity, manipulativeness, callousness, lack of remorse and pathological lying. Factor 2 was believed to measure the antisocial-lifestyle elements of psychopathy, such as impulsivity, proneness to boredom, behavioural problems, irresponsibility and delinquency (Hare, 1991). Subsequently, Cooke and Michie (2001) derived a three-factor structure, consisting o f the facets of interpersonal (glibness, manipulativeness, grandiosity), affective (lack of emotion and affect, lack of remorse, recklessness), and lifestyle (lack o f planning, irresponsibility) psychopathic characteristics. More recently, however, several studies have supported a four-factor model that fits at least as well as the three-factor model (e.g. Hill, Neumann & Rogers, 2004; Vitacco, Neumann, & Jackson, 2005). By including items that were previously excluded from the three-factor model, this new model introduces a fourth facet of antisocial behaviour (Hare, 2003). 6 There is a current consensus that lack of affect and remorse is the core characteristic of psychopathy. However, there is debate as to whether criminal behaviour is a required feature of psychopathy. It has long been argued that psychopaths are not necessarily criminal or likely to be incarcerated (Cleckley, 1941; Hare, 1978). It has been estimated that the prevalence of psychopathy is approximately 1% in the general population, 3.5% in the business world, and upwards of 25% in adult prison populations (Babiak & Hare, 2006; Hare, 2003). However, given the difficulty of identifying and researching successful psychopaths, much current knowledge about psychopathy is based upon the study of incarcerated individuals, and thus little is known about the etiology o f successful psychopaths. As pointed out by Gao and Raine (2010), research findings based upon incarcerated individuals may not generalize to psychopaths in the community, and may pertain more to criminality than psychopathy itself. Additionally, understanding the etiology o f psychopathy in the community may reveal “ protective” factors preventing successful, non-criminal psychopaths from engaging in a criminally deviant lifestyle. Affective Deficit Many researchers believe that a severe affective impairment is at the core of psychopathy, and is what uniquely distinguishes it from other determinants of antisocial behaviour (Blair, 2005; Dawel, O’Keamey, McKone, & Palermo, 2012). Research has demonstrated that psychopaths experience emotions differently than nonpsychopaths. Specifically, psychopaths have been found to exhibit both qualitative and quantitative differences in their ability to experience (Hare, 1993; Marsh, Finger, Schechter, Jurkowitz, Reid & Blair, 2011), perceive (Blair et al., 2004; Wilson, Juodis, & Porter, 2011), and process emotion (Williamson, Harpur & Hare, 1991). For example, Marsh et al. (2011) found 7 that, in contrast to healthy (nonpsychopathic) individuals, adolescents with psychopathic traits report no greater increase in sympathetic arousal during situations that evoke fear than during situations that evoke anger, disgust, or sadness. Further, it was found that psychopathic adolescents reported experiencing fear less frequently, and less strongly, than their peers. Additionally, numerous studies have found that psychopaths exhibit diminished central and autonomic nervous system reactivity during fear-related paradigms such as aversive conditioning (Flor, Birbaumer, Hermann, Ziegler, & Patrick, 2002; Rothemund, Ziegler, Hermann, Gruesser, Foell, Patrick & Flor, 2012) and the anticipation of electrical shock (Hare, 1982). This hyporeactivity in psychopaths has been shown in both reduced skin conductance responses (Hare, Frazelle & Cox, 1978) and abnormal changes in heart rate (Raine, 1997). Additionally, psychopathy has been associated with abnormal processing of affective language. Using a lexical decision task, Williamson, Harpur, and Hare (1991) found that psychopaths, unlike nonpsychopaths, did not respond faster to emotional words than to neutral words. Specifically, psychopaths failed to show behavioural and electrophysiological patterns o f reaction time facilitation or larger amplitude event-related potentials to affective words that are typical in nonpsychopathic individuals. Emotion recognition in others. The majority of research investigating the emotion recognition impairments observed in psychopaths has focused on facial expressions of emotions. It was long postulated that individuals with psychopathy are unable to process facial expressions of primarily negative emotions. For example, Blair et al. (2004) investigated the sensitivity o f psychopathic individuals to six basic emotional expressions (happiness, surprise, disgust, anger, sadness and fear). Psychopathic individuals showed a selective impairment for the recognition of fearful expressions. However, findings from 8 recent meta-analyses (Dawel et al., 2012; Wilson et al., 2011) have indicated that, overall, psychopathy appears to be associated with small recognition deficits for all basic emotions (i.e., fear, anger, sadness, surprise, happiness, and disgust). Additionally, these deficits were apparent for vocal expressions of emotions (Dawel et al., 2012). The results of these meta­ analyses indicate that emotion recognition deficits in psychopathy are pervasive across emotions and modalities. Psychopathy has long been said to be associated with a profound emotional empathy dysfunction (Hare, 1991) resulting in a lack o f regard for the pain and distress of others (e.g., Blair, Jones, Clark & Smith, 1997). Until recently, however, the topic of third-person pain perception (i.e., the ability to infer features of another person’s pain) in psychopathy has been largely unexplored. Caes and colleagues (2012) examined the potential moderating influence of psychopathic traits on female students’ ability to detect pain in others. These researchers found that psychopathic traits were related to a diminished perceptual sensitivity to pain in others. Subsequently, researchers have found differences in the patterns of neural activity in incarcerated psychopaths and incarcerated nonpsychopaths during the perception of other people experiencing pain (Decety, Skelly & Kiehl, 2013). Specifically, brain activation patterns were examined during two empathy-inducing tasks. One task involved viewing brief video clips depicting individuals being harmed (e.g., hand being crushed) and the other task involved viewing facial expressions of pain. In both tasks, psychopathic individuals exhibited significantly less activation in the ventromedial preffontal cortex and orbitofrontal cortex, regions associated with affective mentalizing (i.e., inferring another’s emotional state; Decety et al, 2013). However, psychopathic individuals only exhibited a deficit in areas 9 associated with cognitive mentalizing (i.e., dorsal striatum, dorsomedial preffontal cortex and the anterior cingulate cortex) during the facial expression task. Further, Decety, Chen, Harenski and Kiehl (2013) examined the influence of perspective taking in psychopaths during a pain perception task. Participants viewed visual stimuli of hands and feet in painful situations and were told to imagine either that the situations were happening to them or someone else. Again, the researchers found decreased activation in the neural areas associated with pain empathy in psychopathic individuals during the imagine-other condition. Interestingly, however, psychopathic individuals showed a typical neural response for pain empathy during the imagine-self condition. These results are consistent with the findings of Caes et al. (2012), suggesting that psychopathy may be associated with an impairment in third-person pain perception. Emotion recognition in self. Despite the widespread belief that psychopathy is characterized by an emotional deficit, most of the research has focused on third-person emotional perception and largely neglected the experience and perception of emotions within oneself. In order to address this gap in the research, a recent study (Gao et al., 2012) examined whether psychopaths could appropriately recognize their own body sensations during an emotion-inducing task. Heart rate and skin conductance were measured in psychopaths and nonpsychopaths during a social stressor designed to elicit emotions such as embarrassment and guilt. Psychopathic individuals were found to show deficits in the awareness of their body states. Specifically, nonpsychopathic controls who experienced increased heart rates verbally reported corresponding higher body sensations. This consistency was not observed in psychopaths. This autonomic-body sensation mismatch, termed ‘somatic aphasia,’ was associated with the interpersonal-affective factor of 10 psychopathy. Important to note, it was found that psychopaths verbally reported body sensations similar to those o f nonpsychopathic controls. This finding suggests that psychopaths may describe emotions that they think that they should feel, based on external cues, while not consciously experiencing such cues. As with third-person pain perception, studies of first-person pain perception (i.e., the ability to infer pain in oneself) in psychopathy are rare and contradictory. Some researchers (Fedora & Reddon, 1993; Hare, 1968; Schoenherr, 1964) have reported a heightened threshold for pain induced by electrical stimulation in psychopaths compared with nonpsychopaths, whereas others (Hare & Thorvaldson, 1970; Rothemund et al., 2012) have found no difference in pain tolerance or threshold. Rothemund et al. (2012) did, however, find evidence to suggest that incarcerated male psychopaths may view the same level of painful experience as less unpleasant than nonpsychopaths. Specifically, in an investigation of aversive conditioning, it was found that psychopathic individuals rated the unconditioned stimulus (a painful electric shock) as significantly less unpleasantness than the nonpsychopathic individuals, although they did not differ in their pain ratings. Additionally, Hare and Thorvaldson (1970) found that when incentives were used, psychopaths were willing to tolerate significantly more shock than nonpsychopaths. These preliminary and contradictory findings highlight the need to further examine first-person pain perception in psychopathy while distinguishing between intensity and unpleasantness ratings of noxious stimuli. Theoretical Models of Psychopathy Typical o f many psychological disorders, the etiology of psychopathy is not yet well understood. However, two prominent theories have been used to provide explanations for the 11 symptoms of psychopathy: the somatic marker hypothesis (Damasio, 1994) and the violence inhibition mechanism (VIM; Blair, 1995). The somatic marker hypothesis suggests that damage to the preffontal lobes o f the cerebral cortex (PFC) leads to impaired decision­ making abilities, reflecting a failure to activate autonomic somatic states associated with the anticipation o f reward and punishment. Somatic markers are believed to be created automatically in the prefrontal cortex by connecting experiences with somatic states. Once formed, these somatic markers facilitate decision-making and behavioural regulation by recalling the outcomes that have been associated with particular situations. It is believed that the emotions associated with previous experiences function as alarm signals. These markers alert the individual to the potential negative outcomes of certain actions, thus playing an important role in avoidance learning. Damasio and colleagues have suggested that impairment of the somatic marker system might underlie psychopathy (Damasio, 1994; Damasio, Tranel, & Damasio, 1990). In other words, it is believed that psychopathic individuals may have a deficit in the formation and/or utilization of these affective somatic associations. Neuropsychological findings have provided evidence for the somatic marker hypothesis as a link between psychopathy and prefrontal cortex dysfunction. Neuroimaging data indicate abnormal PFC function and structure in psychopathy, particularly within the ventromedial PFC, orbitoffontal cortex, and anterior cingulate cortex. Additionally, a study involving the Iowa gambling task, used to simulate real-life decision making, found that psychopathic individuals demonstrated the same impaired gambling behaviour as patients with orbitoffontal lesions (van Honk, Hermans, Putman, Montagne, & Schutter, 2002). When applied to psychopathy, the somatic marker hypothesis could be useful in explaining 12 numerous associated characteristics including impulsivity, irresponsibility, risky decision making, and lack of planning/goals. The violence inhibition mechanism (VIM) model stresses the role of empathy in moral behaviour. Blair (1995) proposed that the recognition of fear is critical to prosocial behaviour. Specifically, nonverbal communication of distress (e.g., facial displays of fear or sadness) triggers cognitive processes involved in the recognition of distress by others. This recognition in turn results in empathy, which predisposes one’s withdrawal from violent behaviour. This withdrawal can only occur, however, when individuals can accurately identify the facial expressions o f others. According to Blair (1995), psychopathic individuals are prone to violence and lack moral emotions (such as guilt and empathy) because they are incapable of recognizing the fearful expression in others and thus the VEM is never fully activated. The neurobiological region implicated by this theory is the amygdala. Strong evidence suggests that the amygdala is involved in emotional processing (Phelps & LeDoux, 2005) and numerous studies have found functional (e.g. Blair, 2010) and structural (e.g. Weber, Habel, Amunts & Schneider, 2008; Yang, Raine, Narr, Colletti & Toga, 2009) differences in the amygdalae of psychopaths. For example, Yang and colleagues (2009) found that psychopathic individuals had decreased bilateral amygdala volume compared with controls. Additional support for the VIM model has been provided by studies that indicate psychopathic individuals show a profound impairment in the processing of sad and fearful faces (Dolan & Fullam, 2006; Wilson, Juodis, & Porter, 2011). These two theories o f psychopathy are likely not mutually exclusive and could instead benefit from being considered together (Weber, Habel, Amunts, & Schneider, 2008). 13 The neurological regions involved in both theories (prefrontal cortex and amygdala) are highly interconnected, and structural and functional dysfunctions of these two regions have been associated with psychopathy (Mitchell, Fine, Richell, Newman, Lumsden, Blair & Blair, 2006). Additionally, both theories implicate deficits in empathic processes as features that distinguish the psychopath from the non-psychopathic individual. Moreover, the neural structures involved, including amygdala, frontal cortex and cingulate cortex have all, in numerous studies, been implicated in the first-person and vicarious experiences of pain (e.g., Botvinick, Jha, Bylsma, Fabian, Solomon & Prkachin, 2005; Lamm, Decety & Singer, 2011; Ochsner et al., 2008). Thus, these theories provide ample reason to believe that careful analyses of first-person and third-person experiences of pain will reveal meaningful differences associated with psychopathic traits. Research Question Despite a growing body of evidence indicating that psychopathy entails profound deficits in emotional processing, the particular dysfunction in pain perception remains poorly understood. The studies to date are limited, often contradictory, and restrictive in both their methods and participants. The few available studies (Hare 1968; Fedora & Reddon, 1993; Rothemund et al., 2012) examining pain threshold in psychopaths used incarcerated males and aversive conditioning paradigms. As previously mentioned, the research findings based upon incarcerated individuals may not generalize to psychopaths in the community, and instead pertain more to criminality than psychopathy itself. Furthermore, due to the complexity of conditioning paradigms these studies fail to get directly at the perception of pain. Similarly, the one study that examined the perception of pain in others (Caes et al., 2012) did so with a sample o f all female students using a vicarious conditioning paradigm. 14 In order to address these important gaps in the existing literature on psychopathy, the present study was designed to examine both first-person and third-person perception of pain in a sample of both male and female students. Pain sensitivity was examined using both subjective ratings and psychophysiological measures. Based on the previous literature and theories, it was hypothesized that psychopathic traits would be associated with a decreased subjective experience of pain. Specifically, it was expected that psychopathic characteristics would be related to a higher pain tolerance, lower subjective ratings of pain, and reduced psychophysiological activity. Additionally, based on the findings by Gao et al. (2012), it was hypothesized that individuals high in psychopathic characteristics would display evidence of an autonomic-emotional mismatch or ‘somatic aphasia’. In regards to third-person pain perception, it was hypothesized that psychopathic characteristics would be associated with a deficit in the ability to accurately perceive facial expressions of pain in others (decreased pain sensitivity), as well as a tendency towards lower pain ratings (response bias). It was expected that these differences in pain perception would be most prominent for ratings of the unpleasantness (i.e., the emotional component) of pain. It should be noted that psychopathy was examined in a noncriminal university sample, as opposed to studying diagnosed criminal psychopaths. Although the majority of psychopathy studies take a categorical approach, a dimensional approach to psychopathy has more recently been promoted. Instead of viewing psychopaths as a discrete class of individuals, psychopathy is viewed as a dimension existing along a continuum (Edens, Marcus, Lilienfeld & Poythres, 2006; Guay, Ruscio, Knight, & Hare, 2007). This view of a dimensional structure for psychopathy posits that differences in psychopathic characteristics between individuals represent differences of degree rather than categorical differences. A 15 number o f self-report measures of psychopathic characteristics have been developed that are based on a dimensional model and intended for use in non-incarcerated, non-criminal populations. These measures include the Self-Report Psychopathy Scale-Ill (SRP-III; Williams, Paulhus, & Hare, 2007), the Levenson Self-Report Psychopathy Scale (LSRP; Levenson, Kiehl, & Fitzpatrick, 1995), and the Psychopathic Personality Inventory-R (PPIR; Lilienfeld & Widows, 2005). These self-report psychopathy measures assess psychopathic characteristics on a continuum, and have been found in systematic programs of psychometric research to be reliable and valid measures of noncriminal psychopathy (e.g., Williams, Nathanson, & Paulhus, 2003). Moreover, due to the convenience of recruitment, the majority of studies on non­ incarcerated psychopaths have focused on university students who score relatively high on psychopathic characteristics (Gao & Raine, 2010). University students with psychopathic traits have been found to show similar emotional and cognitive deficits to incarcerated psychopaths, including response modulation deficits, autonomic hyporeactivity, and risky decision making (e.g., Osumi, Shimazaki, Imai, Sugiura & Ohira, 2007; Mahmut, Homewood & Stevenson, 2008; Gao & Raine, 2010). Furthermore, as previously mentioned, research findings based upon incarcerated individuals may not generalize to psychopaths in the community and may pertain more to criminality than psychopathy itself (Gao & Raine, 2010). For these reasons, psychopathy was viewed as dimensional trait and assessed in a university sample. Additionally, perception of pain was examined directly, distinguishing between ratings of pain intensity and unpleasantness in both oneself and others. To my knowledge, this was the first psychopathy study to separately examine pain intensity and unpleasantness 16 ratings in regards to third-person pain perception. Pain has been defined as a complex and multidimensional experience, influenced by both the intensity o f noxious stimulation and by psychological variables (Hofbauer, Rainville, Duncan & Bushnell, 2001; Villemure, Slotnick, & Bushnell, 2003). Numerous studies have demonstrated that pain can be divided into two distinct dimensions that vary independently from one another: a sensorydiscriminative dimension and an affective-motivational dimension (e.g., Hofbauer et al., 2001; Price, Harkins, & Baker, 1987). The sensory-discriminative dimension encompasses the spatial, temporal and intensity properties o f pain; whereas the affective-motivation dimension reflects the unpleasantness of the stimulus, as well as the autonomic and behavioural reaction (Melzack & Casey, 1968; Price et al., 1987). Because psychopathy is characterized by an emotional deficit, measures of both dimensions o f pain experience (i.e., intensity and unpleasantness) were included in this study to allow for a deeper understanding of first-person and third-person pain perception. 17 Methods Data for this study were collected as part of a larger collaborative project investigating the perception of pain and emotion in self and others, as mediated by several personality variables (psychopathy, empathy, alexithymia, and pain catastrophizing). However, only information pertaining to the topic of this thesis will be reported. Participant Sampling and Characteristics Participants were recruited from an online undergraduate subject pool at the University of Northern British Columbia (UNBC). Participants were informed of the study by word-of-mouth, classroom presentations, and the UNBC Psychology Research Participation System. In exchange for participation, students were awarded two course credits and a monetary incentive of fifteen dollars. All participants had normal or corrected vision. Because part of the study involved exposure to experimental pain induced by exposure to cold—a stimulus that increases blood pressure—participants were screened for hypertension. None were excluded on this basis. There were 110 participants (51 males and 59 females) in this study. Their ages ranged from 17 to 30 years (M = 20.22 years, SD = 2.46). Participants predominantly self­ identified as Caucasian (70%), followed by Multiple Ethnicity (12.7%), East Asian (9.9%), South Asian (3.6%), Other (2.7%), First Nations (1.8%). The majority (89%) of participants were right-hand dominant. Apparatus and Materials Two laboratory rooms at UNBC were used for this study, one designated for the researchers and one for the participants. A large one-way window connecting the two rooms allowed the researchers to observe the participants throughout the two experimental tasks. A 18 VTech® Safe & Sound Full Colour Video and Audio Baby Monitor was used to facilitate accurate monitoring and communication with the participant during the cold-pressor task. The researchers’ room contained a Dell Optiplex GX620 personal computer running AcqKnowledge 3.9.0 software to display and record psychophysiological data. The participants’ room contained a Dell Optiplex GX620 computer running SuperLab™ 4.5 stimulus presentation software for the presentation o f stimuli and recording of responses. Participants input their ratings using a Logitech M705 wireless mouse. During both tasks, participants were seated in a reclining chair with their backs facing the researchers. Self-report measures. Demographics. A standard demographics questionnaire was constructed to obtain demographic information on each participant. Information collected included participants’ sex, ethnicity, age, and handedness (Appendix A). Psychopathic characteristics. Psychopathic personality characteristics were assessed using the Hare Self-Report Psychopathy Scale-Ill (SRP-III; Paulhus, Neumann & Hare, 2012; Appendix B). This 64-item self-report scale generates a total score as well as four subscale scores: Interpersonal Manipulation (IPM), Callous Affect (CA), Erratic Lifestyle (ELS), and Antisocial Behaviour (ASB). Participants respond to each item on a scale o f 1 (Disagree Strongly) to 5 (Agree Strongly). Despite the PCL-R being the most widely used measure o f psychopathy, it has several disadvantages that the SRP-III is able to circumvent. Completion of the PCL-R is both time and labour consuming, typically requiring over two hours to administer. Additionally, validation of the PCL-R is primarily based on incarcerated samples. The SRP-III, however, has been found to be a reliable and valid brief measure of noncriminal psychopathy that parallels the four-factor construct measured by the PCL-R (Williams et al., 2003; Williams et al., 2007). Empathy. As lack of empathy is a defining characteristic of psychology, empathy levels were evaluated in addition to psychopathic characteristics. Empathy was assessed using the Toronto Empathy Questionnaire (TEQ; Spreng, McKinnon, Mar & Levine, 2009; Appendix C). The TEQ is an empirically-derived, 16-item, self-report measure. This unidimensional measure characterizes empathy as a primarily emotional process. The TEQ has demonstrated good internal consistency, high test-retest reliability and strong convergent validity (Spreng et al., 2009). Assessment of first-person pain. Pain stimulus. Experimental pain was induced using the cold-pressor task, as it is a safe method with good reliability and validity (Edens & Gill, 1995) and widely used in experimental pain studies. Cold pressor stimulation was created with a 56-litre Coleman Cooler (57.5 cm deep, 44.5 cm long, 45 cm wide) filled with water maintained at 4°C. The water was maintained at a consistent temperature within the commonly accepted standard for cold pressor use in adults —ranging from 0 to 7°C (Mitchell, McDonald & Brodie, 2004). A Tetra Whisper® Aquarium Air Pump was used for continued circulation of the water to avoid heat buildup around the arm (Mitchell et al., 2004). A custom built window screen was attached inside the cooler, providing a barrier to prevent contact between ice and the participant’s arm. Water temperature was monitored using Marina® ThermoSensor Inside/Outside Thermometer with a digital display and temperature range from -50°C to +70°C. The water was initially cooled with the use of crushed iced, after which it was maintained with several large icepacks. A Krups® Intuitive Kettle was used for any necessary temperature adjustments. 20 This pain induction method was approved by the UNBC Ethical Committee, and adhered to the ethical guidelines for pain research in humans as recommended by the International Association for the Study o f Pain (Charlton, 1995). Pain ratings. Subjective experience of pain was evaluated during the cold-pressor task using self-report visual analog scales (VAS). Considerable empirical support has been found for the validity o f VAS in pain measurement, indicating high sensitivity, reliability and positive relationships to other self-report measures as well as to observed pain behaviours using both pen/paper and computer-based scales (Jensen & Karoly, 2011). Additionally, the VAS has been found to be valid and reliable measure for both the intensity and unpleasantness of human pain (Price, McGrath, Rafii & Buckingham, 1983). The scales appeared as 14.5cm (400 pixels) black, horizontal lines, labeled appropriately as either “intensity” or “unpleasantness”. The pain intensity scale was anchored with the verbal descriptors no pain and extremely strong pain ; the unpleasantness scale was anchored with the descriptors no pain and extremely unpleasant pain. Participants made ratings by moving the curser with their right hand to the appropriate position on the scale and left clicking. A green checkmark appeared on the screen to indicate to the participant that the rating had been recorded. Each VAS was presented successively on the computer screen, every fifteen seconds, and preceded by an auditory cue to direct participants’ attention. The presentation order of the scales was randomized for each participant using SuperLab™ 4.5 stimulus presentation software. The first set o f ratings was made immediately following immersion of the arm, and then repeated every fifteen seconds for three minutes or until the arm was removed from the water. In total, each participant made a maximum of twelve intensity ratings and twelve 21 unpleasantness ratings. The pixel position (ranging from -200 to +200) for each rating was subsequently converted to a score from 0 - 1 0 0 . Subjective pain ratings were also evaluated following the cold pressor test with the use of the short-form o f the McGill Pain Questionnaire (SF-MPQ; Melzack, 1987). Participants completed the questionnaire using the point at which they felt the most pain during the cold-pressor as their point of reference for responding. The SF-MPQ has been demonstrated to be a highly reliable measure o f pain (Grafton, Foster & Wright, 2005). The main component of the SF-MPQ consists of 15 descriptors (11 sensory; 4 affective) which are rated on an intensity scale as 0 {none), 1 {mild), 2 {moderate) or 3 {severe). Three pain scores are obtained from the sum of the intensity rank values of the words chosen for sensory, affective, and total descriptors. The SF-MPQ also includes the Present Pain Intensity (PPI) index of the standard MPQ and a VAS (Melzack, 1987). Pain tolerance. Participants were asked to keep their left arm in the water as long as they could and to terminate immersion (withdraw their arm) when they could no longer tolerate the sensation or three minutes had passed. Pain tolerance was taken as the amount of time that elapsed from the moment the participant’s arm was immersed to the moment the participant’s arm was removed from the water. Total seconds of immersion was measured with a digital stopwatch. Psychophysiological measurement. Heart rate (HR) and heart rate variability (HRV) were assessed during the first-person pain task in order to evaluate possible differences in pain sensitivity and regulation. Numerous studies have observed autonomic responses (e.g., increases in heart rate) to pain. For example, Loggia, Juneau and Bushnell (2010) found HR significantly correlated with pain ratings and served as a better predictor of between-subject 22 differences in pain than skin conductance. Heart rate variability (i.e., beat-to-beat differences in HR) is a non-invasive measure thought to reflect the heart’s ability to adjust to changing situational demands (Acharya, Joseph, Kannathal, Lim & Suri, 2006). Unlike other psychophysiological measures, HRV is able to provide information regarding both parasympathetic and sympathetic activity, and in so doing allows for inferences about inhibitory and excitatory processes that have been linked to processes of emotion regulation (Appelhans & Luecken, 2006). Research findings support the utility of HRV as an objective index of the brain’s ability to organize regulated emotional responses through the autonomic nervous system and as a marker of individual differences in emotion regulatory capacity (Appelhans & Luecken, 2006). Pain has been conceptualized as an emotion that motivates homeostatic behaviors (Craig, 2003) which suggests that individual differences in HRV (i.e., emotional responding) may account for variation in pain sensitivity and the ability to regulate pain through various strategies (Appelhans & Luecken, 2006). A continuous electrocardiogram (ECG) was obtained using Biopac physiological recording system and the data was recorded using AcqKnowledge 3.9 software (Biopac Systems Inc.) at a sampling rate of 200 Hz. Three disposable BioPac ECG electrodes were placed in a three-lead chest configuration: the two active electrodes were placed on the right collar bone and the lowest rib on the left side, and the ground electrode was placed on the left collar bone. Physiological parameters were derived from the ECG data using Acknowledge 4.0 software as described in the data reduction section. Several cotton t-shirts in various sizes were modified to facilitate the placement of electrodes. Specifically, three small holes were created in each of the shirts to allow access 23 the left and right collarbone, as well as the left lower rib area. Participants were asked to change into one of these shirts prior to completing the cold-pressor task. Assessment of third-person pain. Video Stim uli Third-person perception of pain was evaluated by having participants observe videotaped recordings of facial expressions selected from the UNBC-McMaster Shoulder Pain Expression Archive (Prkachin & Solomon, 2008; Lucey, Cohn, Prkachin, Solomon & Mathews, 2011). This archive contains video of the faces of adult subjects (129 subjects - 63 male, 6 6 female) with shoulder injuries who participated in a previous study of shoulder pain (Prkachin and Solomon, 2008). These individuals were recorded during active and passive movements o f their affected and unaffected shoulders. Facial expressions o f pain consist primarily of four movements: brow lowering, orbit tightening (narrowing of the eye apertures and raising o f the cheeks), levator tightening (raising of the upper lip and/or nose wrinkling), and eye closure (Prkachin, 1992). These actions have been shown to be graded in intensity (Prkachin & Mercer, 1989) and are correlated with the subjective intensity of pain experience (Prkachin, Berzins & Mercer, 1994; Prkachin & Solomon, 2008). The video files were reviewed to extract samples of three categories of facial expression: moderate pain, low pain, and no pain. These categories were selected in order to produce a test o f sufficient difficulty to capture individual differences in perceptual sensitivity to pain expression. Previous studies of third-person pain using a test that included high-intensity pain expressions have yielded measures of sensitivity that were thought to be too high to capture the range of individual differences anticipated to relate to psychopathic deficits in the present study (e.g., Prkachin, Mass & Mercer, 2004; Prkachin & Rocha, 2010; Wojakiewicz, Januel, Braha, Prkachin, Danziger & Bouhassira, 2013). Each o f the video 24 clips had been previously scored for amount of pain expression using a system based on Ekman and Friesen’s (1978) Facial Action Coding System. The pain actions previously mentioned, with the exception of eye closure, had been rated on an intensity scale ranging from ‘1’ (a trace of the action) to ‘5’ (the action occurs at maximum intensity). Eye closure is rated on a binary scale (1 = present; 0 = absent). Scores for each action were summed to create a total pain expression score that ranges from 0 to 16. Excerpts were considered to display moderate pain if the total score was 4 or 5, low pain if the total score was 2 or 3, and no pain if the total score was 0 . Sixty one-second video clips (20 moderate pain, 20 low pain, 20 no pain) were selected in total. To minimize the influence of disparities in visual images and angle, all clips selected were taken from active range-of-motion tests that provided a relatively direct, frontal view of the patients’ faces. Equal numbers of female and male faces appeared at each intensity level. In addition to meeting the foregoing criteria to be considered as falling into no, low and moderate pain categories, an attempt was made to select clips having relatively homogeneous properties. This was done by inspecting the distribution o f ratings that had been given to a larger sample of stimuli in a previous judgment study (Rash, Prkachin & Campbell, 2014) in which 99 undergraduates had rated each stimulus on a 0 - 10 numeric rating scale. Clips were chosen to minimize variability such that standard deviations of their ratings varied from 1.34 to 2.68 (skewness values ranged from -.41 to 1.62). Pain ratings. Participants were asked to evaluate both the intensity and unpleasantness of pain displayed in each video clip using the same two VAS from the firstperson pain perception task. These scales were presented successively following each video clip. The order of scale presentation was randomized for each participant using SuperLab™ 25 4.5 stimulus presentation software. This process generated 60 intensity ratings and 60 unpleasantness ratings from each participant. Procedure Participants were recruited using an online research participation system at UNBC. All participants were pre-screened for psychopathic and empathy characteristics (i.e., SRP-III and TEQ; Appendix B and C) via the UNBC Psychology Research Participation System prior to attending the first laboratory session. Following completion of the pre-screen, participants made appointments for two laboratory visits using the online system, with the second session occurring four to ten days after the first. The first session was used to collect data reflecting participants’ perception o f their own pain (first-person pain perception), and the second session was used to collect data reflecting participants’ perception of pain in others (third-person pain perception). Upon arrival to the first session, both written and verbal consent were provided prior to the collection of any data. During this process, participants were provided a detailed description of the study, including the purpose of the study, risks and benefits of their participation, and the confidential collection and storage of data. Participants were reminded that their participation was voluntary and they were free to withdraw from the study at any time without penalty. After obtaining consent, participants completed the demographics questionnaire (Appendix A). First-person pain perception. Participants were then asked to leave the laboratory in order to change into a shirt designed to allow access to the clavicle and lower left rib area, to facilitate psychophysiological recording. Upon the participants’ return to the laboratory, they were asked to turn off any cell phones or electronic devices and to remove any watches or jewelry 26 from their left hand that could be damaged by water. A researcher then attached the three electrodes (one under each clavicle and one on the lower left rib) for psychophysiological monitoring, ensuring proper connectivity and comfort. Participants were then read a set of scripted instructions (Appendix D). Because the affective and sensory components of pain are often considered together and thus may not easily be distinguished, the differences between pain intensity and unpleasantness were stressed using explanations implemented by Loggia et al. (2011). Specifically, participants were presented with an auditory metaphor of a dripping faucet in the middle of the night, for which the intensity could be very low, while the unpleasantness could be very high, in order to emphasize the dissociability o f pain affect and sensation. Participants were then reminded to remain as still as possible throughout the experiment so as to reduce ECG movement artifact. Any questions were addressed at this time, after which the researcher left the room to commence the psychophysiological recording. Following a three-minute baseline period, participants were instructed by a researcher via the baby monitor to begin the cold-pressor task. Participants immersed their left arm in the cold water, while simultaneously activating the presentation software by clicking the mouse with their right hand. Immediately after immersing their arm, participants rated the intensity and unpleasantness o f their pain experience using visual analog scales by manipulating the mouse. Cued by an automated auditory signal, participants repeated these ratings every 15 seconds until they withdrew their arm from the water or for a maximum immersion time o f three minutes. Immediately following completion o f the cold-pressor, participants were asked to complete the SF-MPQ, using the point at which they felt the most pain during the task as 27 their point of reference. Participants were then awarded one course credit and reminded of their follow-up visit. Third-person pain perception. When participants arrived for the second session, they were seated in the same spot as in their initial visit. After providing a second informed consent, participants were read a scripted set o f instructions (Appendix D) and any questions were addressed. Participants were again reminded of the distinction between intensity and unpleasantness. They then viewed sixty one-second video clips, after each of which they were prompted to make two VAS ratings. Participants recorded their judgment of the pain intensity and unpleasantness that they believed the patient was experiencing using the same visual analogue scales as in the first-person pain perception task. At the end of the session, participants were debriefed, awarded a monetary incentive, and provided a second course credit. Data Reduction and Statistical Analysis All participants completed a pre-screen questionnaire that included the SRP-III and TEQ using the UNBC Psychology Research Participation System. Raw data from these selfreport measures were downloaded directly into an Excel spreadsheet and scored. First-person pain perception. Pain ratings. During the cold-pressor task, each participant made a set o f pain ratings (intensity and unpleasantness) every fifteen seconds, for a maximum time o f three minutes. This process generated a total o f twelve intensity ratings and twelve unpleasantness ratings for participants who completed the full three minutes. Participants’ pain intensity and unpleasantness VAS ratings were recorded as pixel positions ranging from -200 to +200 (with 0 being the midpoint of the line) and subsequently converted to scores ranging from 0 100. Mean intensity ratings and mean unpleasantness ratings were then calculated. 28 Additionally, these scores were analyzed for pain sensitivity and response bias using magnitude estimation procedures. A regression line was calculated relating each participant’s VAS ratings during the cold pressor test to the time at which the rating took place. The slope of the regression line indicates the rate of growth of pain intensity and unpleasantness with time. This parameter was examined to determine whether psychopathic characteristics influence an individuals’ sensitivity to pain. Additionally, it is possible that psychopathy may influence the overall tendency to apply higher or lower numbers when rating intensity and unpleasantness. This would correspond to a response bias and was indexed by the intercept of the regression between pain ratings and time. The individual slope and intercept values for intensity and unpleasantness, along with SRP-III and TEQ scores, were then analyzed in correlation and regression analyses. Additionally, participants completed a pen-and-paper-based SF-MPQ following the cold-pressor task. Data were entered into an Excel spreadsheet by an undergraduate volunteer. Scores were obtained for the sum of the intensity rank values of the words chosen for sensory, affective, and total descriptors, as well as for the PPI and VAS. These measures were then correlated with SRP-III and TEQ scores. Psychophysiological data. The continuous ECG recording from the AcqKnowledge 3.9 software were reformatted by an undergraduate volunteer into individual files separating baseline from cold-pressor. AcqKnowledge 4.2 software was then used to process the raw ECG data and automatically identify R-waves. The R-R interval series for the first threeminutes (i.e., baseline) were selected and manually corrected for errors due to misidentified R-waves. This was repeated for the cold-pressor task. Visual inspection of the raw ECG was performed to identify and correct artifacts and abnormal beats. Heart rates, in beats per 29 minute, were then calculated from the R-R intervals. Respiratory sinus arrhythmia (RS A) was used to index heart rate variability. RSA values were calculated using an AcqKnowledge algorithm, averaged in one-minute intervals. To control for baseline measures, a change score was then calculated by subtracting the participant’s baseline heart rate from their heart rate during the cold-pressor task. This process was repeated to calculate RSA change scores. Additionally, using methods similar to Gao et al., (2012), autonomic-emotional mismatch scores were computed by calculating the differences between z-standardized heart rate changes and z-standardized pain intensity VAS scores for each participant. This was repeated using pain unpleasantness VAS scores. Higher values would indicate greater autonomic responding relative to subjective pain reports (i.e. heart rate changes > pain intensity or pain unpleasantness) and indicate autonomic-emotional mismatch. Pearson correlation coefficients were then calculated to examine the relations between mismatch scores and SRP-III scores. Third-person pain perception. During the third-person pain perception task, participants completed 60 sets of pain ratings (intensity and unpleasantness), totaling 120 per participant. These VAS ratings for intensity and unpleasantness of others’ pain were analyzed using methods similar to those employed in other studies (e.g., Danziger, Prkachin & Wilier, 2006). Ratings were scored using signal detection procedures for rating-scale tasks (McNicol, 1972). To accomplish this, “no pain” stimuli were considered to be noise, while low- and medium-pain stimuli were considered to be different levels o f signals. Intensity and unpleasantness VAS ratings were separated into ten categories by separating VAS ratings at 0 - 10, 11 - 20...91 - 100. The probability o f using each category to rate noise and the two levels of signal stimuli was 30 calculated and the resulting probabilities accumulated from the highest (91 - 100) to the lowest ( 0 -1 0 ) category for each stimulus. Cumulative probabilities associated with the “no pain” category were then considered to represent false alarms, whereas cumulative probabilities associated with “low-” and “medium-pain” were considered hits. Based on these values, measures o f the discriminability of low pain from no pain and of medium pain from no pain were calculated by measuring the proportion o f the area [P(A)] under the ReceiverOperating-Characteristic (ROC) curve representing the no pain —low pain discrimination and the no pain - medium pain discrimination, by application of the trapezoidal rule. In addition, a third discrimination value was calculated, representing the ability to discriminate between “medium pain” and “low pain” by treating responses to low pain as noise and to medium pain as signal. Response bias is the tendency to distribute ratings systematically toward one or the other end o f a rating scale which, in signal detection analyses, is independent of discriminability. In rating tasks of the sort employed in this study, it can be operationalized by the measure B, which represents the point on a rating scale at which the respondent is equally likely to perform a hit or a false alarm (McNicol, 1972). Thus, three scores were calculated for discrimination [P(A)] and three scores for response bias (B): between no pain and low pain expressions [P(A)NL and BNL]; between no pain and moderate pain expressions [ P ( A ) n m and Bnm]; and between low pain and moderate pain expressions [ P ( A ) l m and Bu^l-The discrimination scores, P(A), signify the extent to which individuals are able to differentiate between different intensities of facial expressions and may vary between 0 and 1. A score of 0.5 represents chance and indicates no discrimination at all, while a score of 1.0 indicates perfect discrimination. The response bias 31 scores, B, correspond to the point on the participant’s rating scale at which, by interpolation, the sum o f the hit and false alarm probabilities equals 1.0. This score represents an individual’s propensity to infer pain from the facial expressions or, in other words, their tendency to systematically make ratings at one or the other end of the rating scales. The three discriminability and three response-bias scores resulting from analyses based on intensity and unpleasantness ratings were then correlated with SRP-III scores. All analyses were conducted using SPSS v.22. Missing Data and Outliers Assumptions of normality were successfully met in that all data from this large sample (N= 110) were normally distributed (as per examination of histograms, box-plots, skewness and kurtosis values). In terms of outliers, eight participants were identified as high scoring outliers on the SRP-III and its subscales. However, because the main objective of the study was to examine the relationship between higher levels of psychopathic traits and pain perception, the decision was made to retain the high-scoring univariate outliers. Additionally, these individuals did not appear to differ from the rest of the sample on other traits. Missing data were excluded from analyses. In the first-person pain task, one participant’s VAS during the cold-pressor task failed to record and was therefore not included in the analysis. Complete psychophysiological data for two participants were removed due to recording equipment malfunction. Due to insufficient data, RSA values and change scores could not be calculated for participants who withdrew their arms from the cold-pressor task before three minutes had elapsed (N= 13). Five participants failed to attend the second laboratory session and were thus not included in the third-person perception of pain analyses. 32 Results Personality Variables Descriptive statistics for the SRP-III and TEQ are presented in Table 1. As shown in Table 1, reliability o f the overall SRP-III scale was .92 (Cronbach’s alpha). Reliabilities for the four subscales ranged from .78 to .83. These reliabilities are similar to those of the normative sample o f undergraduate students for the measure (Appendix B). Reliability of the TEQ was .82. The reliabilities were above the commonly-used acceptable cut off of .70 (Nunnally & Bernstein, 1994), and as such, all scales were included as variables in further analyses. Table 1 Descriptive Information From the SRP-III and TEQ N Minimum Maximum Mean SD a Total 110 1.38 3.27 2.23 0.40 .92 IPM 110 1.31 3.75 2.52 0.52 .83 CA 110 1.44 3.75 2.36 0.48 .78 ELS 110 1.38 4.19 2.61 0.56 .82 ASB 110 1 .0 0 3.38 1.42 0.43 .79 TEQ 110 25.00 58.00 45.58 7.12 .82 Note. Total = SRP-III total, IPM = Interpersonal Manipulation, CA = Callous Affect, ELS = Erratic Lifestyle, ASB = Antisocial Behaviour, TEQ = Toronto Empathy Questionnaire, a = Cronbach’s alpha. Mean overall scores and subscale scores for the SRP-III and TEQ are presented in Table 1. The mean score on the SRP-III was 2.23 (out of a possible 5; SD = 0.42), with scores ranging from 1.38 to 3.27. The mean scores on the SRP-III were similar to those of the normative sample of undergraduate students for the measure (Appendix B). 33 Scores were then examined to determine whether there were any significant differences between male and female participants. Means and standard deviations, broken down by gender, are presented in Table 2. Independent sample t-tests revealed that males scored significantly higher than females on the SRP-III total scale, /(108) = 4.97, p < .001, the DPM subscale, /(108) = 3.30, p = .001, the CA subscale, /(108) = 6.64,/? < .001, the ELS subscale, f(108) = 2.84,/? = .005, and the ASB subscale, /(108) = 3.07,/? = .003. Females scored significantly higher than males on the TEQ, /(108)=5.00,/? < .001). Table 2 Means and Standard Deviations fo r the SRP-IIIfor Males and Females Total Males: Mean SD Females: Mean SD PM CA ELS ASB TEQ 2.41 2 .6 8 2.63 2.77 1.55 42.28 0.38 0.49 0.46 0.54 0.49 1.04 2.07 2.37 2 .1 2 2.47 1.31 48.44 0.35 0.50 0.35 0.55 .050 0.70 Note. Total = SRP-III total, P M = Interpersonal Manipulation, CA = Callous Affect, ELS = Erratic Lifestyle, ASB = Antisocial Behaviour, TEQ = Toronto Empathy Questionnaire. Table 3 presents the correlations between SRP-III scales and the TEQ. The SRP-III subscales were moderately correlated with one another, as would be expected. Additionally, the SRP-III was negatively correlated with the TEQ, particularly for the CA subscale. The correlations were in the same direction for the P M and ASB subscales, although they were not significant. 34 Table 3 Pearson Correlations between Personality Variables Total IPM Total IPM CA ELS ASB TEQ 1 .825** 824** .802** -.336** .640** .518** .733** 4 4 9 ** ** -.476** 1 CA .508** 1 ELS 4 95 .466** 1 ASB 1 TEQ -.184 -.1 2 2 -.328** 1 Note. Total = SRP-III total, IPM = Interpersonal Manipulation, CA = Callous Affect, ELS = Erratic Lifestyle, ASB = Antisocial Behaviour, TEQ = Toronto Empathy Questionnaire. * p < .05. **p < .01. First-Person Pain Perception Descriptive information for responses during the cold-pressor task is presented in Table 4. As is evident in Table 4, the majority of participants (N = 97) endured the coldpressor task for the full three minutes. On average, participants reported moderate levels of pain intensity and unpleasantness from the cold-pressor stimulation as indicated by the visual analog scale ratings. Figure 1 presents average pain intensity and unpleasantness VAS ratings across the three minute cold-pressor task. The figure shows that both intensity and unpleasantness ratings increased in a linear fashion until approximately 90 seconds into the task, at which point pain ratings tended to level off and decrease. Pain tolerance was significantly inversely correlated with average unpleasantness VAS ratings (r = -.206, p = .031) and the affective component of the SF-MPQ (r = -.223, p = .019). Change in heart rate significantly correlated with both average intensity VAS ratings (r = .325, p = .002) and average unpleasantness VAS ratings (r = .300, p = .003). 35 Table 4 Descriptive Information From the Cold-Pressor Task. N Minimum Maximum Mean SD Tolerance (s) 110 16.00 180.00a 166.24 38.92 Pain Intensity VAS 109 5.31 98.00 50.64 20.72 Pain Unpleasantness VAS 109 0.98 97.83 57.02 23.00 HR Change 94 -11.98 36.86 6.53 8.05 Sensory 110 3.00 30.00 12.64 5.24 Affective 110 0 .0 0 1 0 .0 0 1.85 2.28 Total 110 3.00 40.00 14.48 6.97 VAS (0-10) 110 0.40 1 0 .0 0 5.75 2.13 1 .0 0 5.00 PPI 110 a Ninety-seven participants reached the maximum of 180s. 2.55 0.82 SF-MPQ 70 j —♦— Intensity —#■—Unpleasantness 10 - - 0 -J ! 30 1----------- 1------------ ------------S------------1------------1------------1------------1------------1------------ 1----------- 1------------ 1------1 0 15 45 60 75 90 105 120 135 150 165 Time in Seconds Figure 1. Mean intensity and unpleasantness ratings across all time points in cold-pressor task. 36 Pain tolerance. It was predicted that psychopathic characteristics would be related to differences in the subjective experience of pain. Specifically, it was expected that psychopathic characteristics would be related to a higher pain tolerance during the coldpressor task. Pearson r correlations are shown in Table 2. This hypothesis was not supported. In fact, the opposite effect was observed as indicated by significant negative correlations between pain tolerance and the subscales for Interpersonal Manipulation (r = -.247, p = .009) and Antisocial Behaviour (r = -.216,/? = .023). A stepwise multiple regression analysis was then conducted to evaluate the predictive influence of IPM and ASB scores on pain tolerance. In this procedure only variables exceeding a pre-set significance threshold (in this case .05) are included in the regression. Variables not reaching this threshold are not included in the equation. Interpersonal Manipulation was significantly related to pain tolerance, F (l, 108) = 7.00, (3 = -.25, p = .009, accounting for approximately 5.20% of the variance. Antisocial Behaviour did not enter into the equation as a significant independent predictor (t = -1.67, p = -.13,p =.209). Pain tolerance was not significantly correlated with TEQ scores. Pain ratings. It was expected that psychopathic characteristics would be associated with lower subjective ratings of pain during the cold-pressor task. Pearson r correlations are shown in Table 5. This hypothesis was not supported; average pain ratings from the coldpressor task did not significantly correlate with SRP-III scores. Next, slope and Y-intercept values for pain intensity and pain unpleasantness VAS ratings were examined in order to determine whether psychopathic characteristics influence differences in first-person pain sensitivity or response bias. It was originally hypothesized that psychopathic characteristics would be related to decreased pain sensitivity and a negative response bias. As seen in Table 5, no significant correlations were found between these measures and SRP-III scores, failing 37 to support the hypothesis. TEQ scores did not significantly correlate with any subjective pain ratings. Table 5 Pearson r Correlations Between Responses During the Cold-Pressor and SRP-III Scores. Total IPM CA ELS ASB TEQ -.059 -.026 -.216* .063 Pain Intensity VAS -.133 -.146 -.156 -.105 -.006 -.053 Intensity Slope -.074 -.1 0 0 -.072 .070 .155 -.072 t © u> -.247** .0 1 1 Intensity Y-Intercept .050 .003 OO -.167 © 1* Pain Tolerance .042 Pain Unpleasantness VAS -.106 -.128 -.154 -.083 .041 -.034 Unpleasantness Slope -.116 -.064 -.093 -.099 -.1 2 1 .128 Unpleasantness Y-Intercept .054 .0 2 2 -.030 .053 .146 -.076 Sensory -.064 .017 -.092 -.067 -.067 .074 Affective .027 .063 -.064 .035 .049 .045 Total -.039 .034 -.090 -.039 -.035 .070 VAS (0-10) -.153 -.153 -.1 1 0 -.1 1 0 -.038 -.0 1 1 PPI -.085 -.013 -.075 -.075 -.066 -.043 Note. Total = SRP-III to tal, IPM = Interpersonal Manipulation, CA = Callous Affect, ELS = Erratic Lifestyle, ASB = Antisocial Behaviour, TEQ = Toronto Empathy Questionnaire. * p < .05. **p < .01. Psychophysiological data. It was hypothesized that psychopathic characteristics would be related to reduced physiological activity during the cold-pressor task. Pearson r correlations are shown in Table 6 . This hypothesis was not supported. However, as seen in Table 6 , average baseline HR correlated negatively with SRP-III total scores {r = -.210,/? = .030). This effect was also observed for the subscales Interpersonal Manipulation, Erratic Lifestyle, and Antisocial behaviour. However, no significant differences in HR were found during the cold-pressor task when examining average heart rate or change in HR. No significant correlations were found between RSA values and SRP-III scores. Next, Pearson correlation coefficients were examined to determine the relationship between pain intensity- and unpleasantness-derived mismatch scores and SRP-III scores (see Table 6 ). It was hypothesized that psychopathic characteristics would be related to higher mismatch scores, indicating an autonomic-emotional mismatch. As shown in Table 6 , this hypothesis was supported. Significant positive correlations were found between the autonomic-intensity rating mismatch score and SRP-III total scores (r = .295, p = .004) and between the autonomic-unpleasantness rating mismatch score and SRP-III total scores (r = .304,/? = .003), indicating that individuals with a higher mismatch between their heart rate and subjective pain ratings were higher in psychopathic characteristics. This effect was also observed for the subscales IPM, CA, and ELS. 39 Table 6 Pearson r Correlations Between Psychophysiological Variables and Personality Characteristics IPM CA ELS ASB TEQ BHR -.2 1 0 * -.203* -.027 -.208* -.223* I o u> Total CPHR -.128 -.109 .062 -.196 -.153 -.174 AHR .158 .155 .116 .095 .146 -.070 BRSA .097 .105 .014 .090 .098 .1 2 2 CPRSA .078 .155 .116 .095 -.072 .224* ARSA -.026 -.028 .037 -.072 -.007 -.092 Mismatch-Int .295** .296** .266** .2 1 2 * .155 .004 Mismatch-Unp .304** .298** .289** .2 0 0 .017 -.051 Note. Total = SRP-III total, IPM = Interpersonal Manipulation, CA = Callous Affect, ELS = Erratic Lifestyle, ASB = Antisocial Behaviour, TEQ = Toronto Empathy Questionnaire, BHR = baseline heart rate, CRHR = heart rate during the cold-pressor, AHR = change in heart rate from baseline to cold-pressor, BRSA = baseline respiratory sinus arrhythmia, CPRSA = respiratory sinus arrhythmia during the cold pressor, ARSA = change in respiratory sinus arrhythmia from baseline to cold-pressor, Mismatch-Int = Mismatch score between heart rate and intensity ratings, Mismatch-Unp = mismatch score between heart rate and unpleasantness rating. * p < .05. ** p < .01. Stepwise multiple regression analyses were then used to evaluate the predictive influence o f the SRP-III subscales on mismatch scores. Interpersonal Manipulation was significantly related to the intensity-derived mismatch scores, F (l, 91) = 8.716, p = .30,p = .004, accounting for approximately 8% o f the variance (R2 = .077). The remaining three subscales did not enter the equation as significant predictors. Additionally, Interpersonal Manipulation was significantly related to the unpleasantness-derived mismatch scores, F( 1, 91) = 8.88, P - .30, p = .004, accounting for approximately 8% o f the variance (R2 = .079). Again, the other three subscales did not enter the equation. 40 Third-Person Pain Perception Response bias and discriminability scores were calculated for both pain intensity and unpleasantness ratings for each level of discrimination (no pain versus low pain, no pain versus moderate pain, and low pain versus moderate pain). Descriptive statistics for these parameters are presented in Table 7. It cam be seen that, on average, participants had the highest discrimination score when distinguishing between the no pain clips and moderate pain clips, as would be expected. Repeated-measures ANOVAs revealed that discriminability scores differed significantly among the three levels of discrimination for pain intensity, F(2, 208) = 97.613,p < .001, and pain unpleasantness, F(2, 208) = 87.782, p < .001. Additionally, response bias scores differed significantly among the three levels of discrimination for intensity, F(2, 208) = 92.905,p < .001, and pain unpleasantness, F(2, 208) = 103.825,/) < .001, with the highest response bias occurring when distinguishing between the low pain and moderate pain clips. 41 Table 7 Descriptive Information fo r Discrimination and Response Bias Scores N Mean SD No vs Low 105 .637 .098 No vs Moderate 105 .733 .113 Low vs Moderate 105 .612 .077 No vs Low 105 .643 .106 No vs Moderate 105 .747 .114 Low vs Moderate 105 .623 .080 No vs Low 105 2.42 1.69 No vs Moderate 105 2.78 1.79 Low vs Moderate 105 3.45 2.06 No vs Low 105 2.99 1.71 No vs Moderate 105 3.52 1.76 Low vs Moderate 105 4.38 2.14 Discriminability Intensity: Unpleasantness: Response Bias Intensity: Unpleasantness: Note. The discrimination scores indicate the extent to which participants were able to differentiate facial expressions and the response bias scores indicate participants’ tendency to infer pain from the facial expressions. Figure 2 presents a receiver operating characteristic (ROC) curve of participants’ average performance during the third-person pain perception task derived from the pain intensity VAS ratings. An ROC curve is created by plotting the true positive rate (i.e., hits) against the false positive rate (i.e., false alarms). Perfect classification of the pain clips, or 42 100% discrimination, would be indicated by a point in the upper left comer (i.e., coordinates 0, 1). Chance performance would be indicated by any point along the diagonal line. Points above the diagonal line represent discrimination greater than chance. In Figure 2, it can be seen that participants as a whole performed better than would be expected by chance for all levels of discrimination (no versus low pain, no vs moderate pain, and low versus moderate pain), with the highest level of discrimination occurring between the no pain and moderate pain clips as would be expected. Independent, single-sample t-tests revealed that pain intensity-derived discriminability scores significantly differed from .5 (i.e., chance) for no pain versus low pain (/ = 14.294,p < .001), no pain versus moderate pain (t = 21.204,p < .001), and low versus moderate pain (t = 14.916, p < .001). Similarly, pain unpleasantnessderived discriminability scores significantly differed from .5 for no pain versus low pain (t = 13.744p < .001), no pain versus moderate pain {t = 22.120, p < .001), and low pain versus moderate pain (t= 15.735, p < .001). 43 1.00 — Chance — NL —A— NM - • LM 0.90 0.80 0.70 0.60 0.50 a. 0.40 0.30 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 p(FA) Figure 2. ROC Plot o f Participants’ Average Performance for Third-Person Pain Perception, p (Hit) = probability of a hit, p (FA) = probability of a false alarm, chance = level of chance performance on task, NL = discrimination between no versus low pain clips, NM = discrimination between no versus moderate pain clips, LM = discrimination between low versus moderate pain clips. It was originally predicted that SRP-III scores would be related to a reduced ability to accurately perceive others’ pain (i.e., decreased pain sensitivity), as well a tendency to make ratings at the low end of the pain scale (i.e., negative response bias). As shown in Table 8, there were no significant correlations between response bias scores and scores on the SRP-III scales, suggesting that psychopathy characteristics were not related to an individual’s propensity to impute pain to others. Similarly, response bias scores were not significantly correlated with the TEQ. 44 Table 8 Pearson r Correlations Between Response Bias and Personality Characteristics Total IPM CA ELS ASB TEQ No vs Low .112 .174 -.008 .128 .042 .089 No vs Moderate .072 .149 -.033 .104 -.012 .114 Low vs Moderate -.028 .028 -.124 .060 -.069 .153 No vs Low .059 .133 -.017 .097 -.050 .099 No vs Moderate .008 .084 -.048 .050 -.081 .118 Low vs Moderate -.064 -.005 -.124 .012 o o r .156 Intensity: Unpleasantness: Note. The response bias scores indicate participants’ tendency to infer pain from the facial expressions. Total = SRP-III total, IPM = Interpersonal Manipulation, CA = Callous Affect, ELS = Erratic Lifestyle, ASB = Antisocial Behaviour, TEQ = Toronto Empathy Questionnaire. * p < .05. **/?<.01. Next, correlations between discriminability scores and SRP-III scores were examined. As seen in Table 9, significant positive correlations were found between discriminability scores and SRP-III total scores for each level of discrimination, for both pain intensity and unpleasantness ratings. In regard to the SRP-III subscales, significant positive correlations were also observed, particularly for the pain unpleasantness ratings. These results support the hypothesis that psychopathic characteristics are related to a reduced ability to accurately perceive pain in others. Figure 3 presents an ROC curve of participants’ performance when distinguishing between no pain and moderate pain clips, broken down by high and low psychopathy scores (determined using a median split). It can be seen that although participants scoring high in psychopathic characteristics performed at a level better than 45 chance, they were significantly worse at the task than those scoring low in psychopathic characteristics. No significant correlations were found between the TEQ and discriminability scores. Table 9 Pearson r Correlations Between Discriminability and Personality Characteristics Total IPM CA ELS ASB TEQ No vs Low -.193* -.158 -.211* -.058 -.196* .059 No vs Moderate -.275** -.177 -.226* -.155 -.329* .116 Low vs Moderate -.198* -.114 -.078 -.188 -.254* .030 No vs Low -.211* -.197* -.212* -.084 -.180 .142 No vs Moderate -.344** -.293* -.307** -.196* -.294** .187 Low vs Moderate -.265** -.211* -.211* -.208* -.208* .062 Intensity: Unpleasantness: Note. The discrimination scores indicate the extent to which participants were able to differentiate facial expressions. Total = SRP-III total, IPM = Interpersonal Manipulation, CA = Callous Affect, ELS = Erratic Lifestyle, ASB = Antisocial Behaviour, TEQ = Toronto Empathy Questionnaire. * p < .05. * * p < . 01. 46 1.00 0.90 0.80 —■— Low SRP — High SRP —— Chance 0.70 0.60 10.50 0.40 0.30 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 p(FA) Figure 3. ROC Plot of Participants Scoring High and Low in Psychopathy at No Versus Moderate Pain. Low and High SRP-III scores were determined using a median split, p (Hit) = probability o f a hit, p (FA) = probability of a false alarm. 47 Discussion Overview of Results It is so frequently stated that it is almost an article of faith that psychopathy entails profound deficits in emotional processing; emotion recognition deficits (Dawel et al., 2012; Wilson, Juodis & Porter, 2011), diminished fear-potentiated startle (Caes et al., 2012; Patrick, Bradley & Lang, 1993), poor fear-conditioning (Hare, 1978), reduced physiological reactivity to aversive stimuli (Gao & Raine, 2010; Lorber, 2004). Pain shares many features with the emotions, including a prominent affective-motivational component (Melzack & Casey, 1968), overlapping central nervous system organization (Etkin, Egner & Kalisch, 2011; Shackman, Salomons, Slagter, Fox, Winter & Davidson, 2011) and obvious relevance to the behaviour o f people who have been characterized as psychopathic. There have been a few studies that have suggested the presence of differences in pain processing among psychopathic individuals; however, the particular dysfunction in pain perception has remained poorly understood. This study directly investigated the influence of psychopathic characteristics and empathy levels on the perception of pain in oneself and others. It was hypothesized that psychopathic traits would be associated with a higher pain tolerance, lower subjective ratings of pain, reduced psychophysiological activity, and a mismatch between pain ratings and autonomic activity. In regards to third-person pain perception, it was hypothesized that psychopathic characteristics would be associated with a decreased sensitivity to others’ pain, as well as a tendency towards lower pain ratings (response bias). Overall, the findings were partially in line with the hypotheses. Contrary to the first hypothesis and to common belief, results of the present study indicate that psychopathic characteristics are not associated with a reduced experience of 48 pain. Specifically, individuals high in psychopathic characteristics exhibited a lower pain tolerance than individuals low in psychopathic characteristics and showed no significant differences in their subjective pain ratings or physiological activity. Despite these paradoxical findings with respect to conventional measures of pain sensitivity, other findings from the present study suggest that psychopathic characteristics are associated with important psychophysiologic differences during the experience of pain. That is, high levels of psychopathic characteristics were associated with a mismatch (or incongruence) between individuals’ subjective ratings of pain and physiological activity. Specifically, individuals low in psychopathic characteristics that showed increased heart rate during the cold-pressor task reported higher levels of pain intensity and unpleasantness. This correspondence between heart rate activity and pain ratings was not found for individuals high in psychopathic characteristics. Lastly, results of the present study suggest that psychopathic characteristics are associated with decreased sensitivity to others’ pain. Specifically, individuals high in psychopathic characteristics were found to have a decreased ability to accurately perceive facial expressions of pain in others. These characteristics were not associated with a response bias. Overall, these findings provide novel insights into the emotional processing deficits associated with psychopathy and expand current theories. First-Person Pain Perception It is commonly believed that psychopaths lack the ability to feel emotions, such as guilt, remorse, fear, and anxiety (Cleckley, 1941; Hare, 1970). Consistent with this notion, studies have shown that psychopaths exhibit differences in their subjective experience of emotions, such as fear and anxiety (Hare, 1993; Marsh et al. 2011; Patrick, 1994). For 49 example, Marsh et al. (2011) found that individuals who were high in psychopathic traits reported experiencing fear less frequently, and less strongly, than their peers. Based on these findings, one can expect that psychopaths may exhibit a decreased subjective experience of pain. Additionally, evidence from numerous studies suggests that psychopaths are unresponsive to certain types o f punishments (e.g., Hare, 1968; Newman & Kosson, 1986, Schmauk, 1970). Schmauk (1970) found that psychopaths were significantly less responsive in terms of anticipatory arousal, subjective anxiety and avoidance learning than nonpsychopaths to physical punishment (i.e., shocks), but were equally responsive to tangible punishment (i.e., loss o f money). Additionally, Hare (1968) found that psychopaths had a significantly higher detection threshold than nonpsychopaths for electric shock. A possible explanation for these findings is that psychopaths are less sensitive to pain, making them inured to the immediate effects of physical punishment and thereby unlikely to be dissuaded from the threat or infliction of pain. For these reasons, it was hypothesized that psychopathic characteristics would be related to a reduced subjective experience of pain. Specifically, it was expected that individuals high in psychopathic characteristics would exhibit a higher pain tolerance, lower subjective ratings of pain, and reduced physiological activity during a painful experience relative to individuals low in psychopathic characteristics. These hypotheses were not supported. As previously mentioned, some researchers (e.g., Fedora & Reddon, 1993; Hare, 1968; Schoenherr, 1964) found a heightened pain threshold in psychopaths, whereas others found no difference in pain tolerance or threshold (Hare & Thorvaldson, 1970, Rothemund et al., 2012). Contrary to expectation and adding to the inconsistency of the literature, findings from the present study revealed significant negative correlations between pain tolerance and 50 the SRP subscales for Interpersonal Manipulation and Antisocial Behaviour. While the majority of participants were able to remain in the cold-pressor for the duration of task, individuals high in IPM, in particular, were significantly more likely than individuals low in these characteristics to withdraw early. It should be noted that the previous studies mentioned examining pain tolerance and threshold all used male offenders and electrical stimulation. As such, it could be argued that the inconsistency seen may have to do with the pain induction method used or population examined. Indeed, when a recent study (Miller, Rausher, Hyatt, Maples & Zeichner, 2014) examined the influence of psychopathic traits on pain tolerance in a community sample, it was found that psychopathic traits were related to an increased pain tolerance for pressure and electric shock, but not for cold temperature. Taken together, these findings suggest that the association between psychopathy and pain tolerance may be dependent on the type o f pain administered. Although a lower pain tolerance could indicate an increased experience of pain, results from this study do not support such an interpretation. The subjective pain ratings of individuals scoring high in psychopathic characteristics did not differ significantly from the ratings o f individuals scoring low in psychopathic characteristics. Specifically, psychopathic characteristics did not correlate with overall intensity or unpleasantness ratings, pain sensitivity, or response bias. As shown in Figure 4, individuals scoring high in psychopathic characteristic displayed a similar trend in their self-reported pain to those scoring low in psychopathic characteristics, with intensity ratings increasing in a linear fashion for approximately 90 seconds, at which point pain ratings tended to level off and decrease. 51 -«• — Low SRP ♦— High SRP 60 M C *5 50 0 15 30 45 60 75 90 105 120 135 150 165 Time in Seconds Figure 4. Mean intensity rating across time during the cold-pressor. Low and High SRP-III scores were determined using a median split. These findings are somewhat unexpected. For example, Marsh et al. (2011) found that individuals with psychopathic traits reported experiencing fear less frequently, and less strongly, than their peers. Additionally, Rothemund et al. (2012) found evidence to suggest that psychopaths view the same level of painful experience as less unpleasant than nonpsychopaths. However, other research has suggested that psychopaths report similar emotional experiences to controls. For example, following an anxiety-inducing task, Gao et al. (2012) found that psychopaths’ verbal reports o f body sensations were not significantly different from those o f nonpsychopaths. It was predicted that individuals high in psychopathic characteristics would display evidence of autonomic hyporeactivity during the cold-pressor task. It has long been hypothesized that the antisocial behaviours associated with psychopathy are a result o f a lack of arousal, fear and anxiety (e.g., Hare, 1978). The low-arousal theory proposed by Hare 52 (1970) suggested that psychopaths have a low level of autonomic and cortical arousal, compared with nonpsychopaths, and consequently are in a chronic state o f stimulation and sensation seeking. It has been argued that low resting HR is one of the best replicated biological markers of antisocial and aggressive behaviour (Raine, 2002). Consistent with this notion, findings from the present study revealed that individuals high in psychopathic characteristics had a significantly lower resting HR than individuals low in psychopathic characteristics. However, although baseline HR was negatively correlated with SRP-III total and subscales scores, no significant differences in HR related to SRP-III scores were found during the cold-pressor task when examining average heart rate or change in HR. Additionally, no significant correlations were found between RSA values and SRP-III scores. These findings suggest that individuals high in psychopathic characteristics are no less (or more) likely to experience autonomic changes during a painful experience. These results provide further evidence that the decreased pain tolerance observed in individuals high in psychopathic characteristics is not a result of increased pain experience. Again, these findings are somewhat unexpected as numerous studies have indicated reduced autonomic activity in psychopathic individuals during fear-related paradigms such as anticipation o f electrical shock (e.g., Flor et al., 2002; Hare, 1982; Rothemund et al., 2012). However, in the study by Gao et al. (2012), although psychopaths were found to have lower heart rate responses than the nonpsychopathic individuals during an anxiety-inducing task, the variances in their autonomic measures were comparable at each time point. Taken together, these findings appear to suggest that psychopathic characteristics are not related to differences in the subjective experience of pain. However, the question remains of why psychopathic characteristics would correlate with a reduced pain tolerance if these 53 individuals are not experiencing higher levels of pain. The low tolerance levels seen may instead be a reflection of the personality characteristics associated with psychopathy. For example psychopaths are well known for their selfishness, hedonism, and tendency to avoid discomfort (Checkley, 1964; Hare, 1970; Kajonius, Persson & Jonason, 2015). With these traits in mind, it is easy to imagine that individuals high in psychopathic traits are simply less willing to endure pain than individuals low in these traits when there are no benefits for them to gain. Consistent with this notion, Hare and Thorvaldson (1970) found no difference in pain tolerance between psychopaths and nonpsychopaths without the use of incentives; however, when incentives were used, psychopaths were willing to tolerate significantly more shock than nonpsychopaths. Additionally, it should be noted that the negative correlation between tolerance and psychopathic characteristics was associated with the IPM scale of the SRP-III. In a recent study (Gaughan, Miller & Lynam, 2012), it was found that the IPM subscale of the SRP-III significantly and negatively correlated with the Compliance (r = -.49), Dutifulness (r = -.37), and Self-Discipline (r = -.19) facets o f the NEO Personality Inventory Revised (NEO PI-R). These findings suggest that individuals high in interpersonal manipulation may feel less of a need to comply and complete the full task than individuals low in these traits, resulting in a lower pain tolerance. As previously stated, psychopathic characteristics were not related to significant differences in subjective reports of pain or cardiovascular activity during the cold-pressor task. Interestingly, however, there was a subtle difference in the linkage between subjective pain and physiological activity revealed upon closer examination. Across participants taken as a whole, individuals’ changes in heart rate were significantly correlated with their ratings of the intensity and unpleasantness of the pain they were experiencing. That is, on average, 54 individuals reported higher subjective ratings of pain intensity and unpleasantness when they experienced increases in their heart rate during the cold-pressor task. However, as hypothesized based on the work of Gao et al. (2012), psychopathic characteristics were related to a mismatch between subjective reports o f pain and the objective autonomic measure o f heart-rate change. In other words, individuals scoring high in psychopathic characteristics did not exhibit the same tendency as those scoring low in psychopathic characteristics to report higher levels of pain when experiencing increased heart rate. This inconsistency between subjective pain ratings and changes in physiological activity was predicted based on the concept o f “somatic aphasia” described by Gao et al (2012). These researchers theorized that if emotional experiences arise from direct perception of body changes, as proposed by James (1884), then the emotional deficit characterizing psychopathy may a result of decreased sensitivity to their body changes during an emotional event. They termed this inaccurate identification and recognition of one's own somatic states “somatic aphasia.” As previously mentioned, Gao et al. (2012) found that psychopathic individuals exhibited a decreased ability to identify their own bodily sensations during an emotioninducing task. Similarly, this deficit was most strongly associated with the interpersonalaffective factor o f psychopathy. The findings from the present study are consistent with those o f Gao et al. (2012) and suggest that somatic aphasia in psychopathy extends to other negative affect experiences. That is, that this autonomic-emotional mismatch occurs not only in anxiety-inducing situations, but also in pain-inducing situations. Interestingly, in the study by Gao et al., the significant association between psychopathic characteristics and the autonomic-body sensation mismatch was observed for skin conductance-derived mismatch 55 scores and not for heart rate-derived scores. However, for psychopaths, those reporting high body sensations and those reporting low body sensations did not differ significantly in heart rate. As skin conductance was not measured in the present study, it is unclear whether a generalized autonomic difference exists. Given that there were no differences found in physiological activity during the pain task, it is unlikely that this somatic aphasia effect is a result of reduced physiological activity. Additionally, and similar to the findings of Gao et al. (2012), the subjective pain ratings of individuals scoring high in psychopathic characteristics did not significantly differ from the ratings o f individuals scoring low in psychopathic characteristics. These findings could suggest that psychopathic individuals are less sensitive to the physiological cues of emotion and thus may be more reliant on external cues for gauging their experience. For example, they may instead report experiences or sensations that they think they should feel based on previous knowledge or social demand characteristics. In line with this idea, research has found that psychopathy is positively correlated with general deception and socially desirable responding (e.g., Book, Holden, Starzyk, Wasylkiw & Edwards, 2006; Seto, Khattar, Lalumiere, & Quinsey, 1997). Interestingly, the somatic aphasia effect was positively correlated with the interpersonal manipulation subscale of the SRP-III in this study and with the interpersonalaffective factor of the PCL-R in the study by Gao et al. (2012). Damasio (2000) has suggested that forming connections between stimuli and physiological changes (i.e., somatic markers) can result in “secondary emotions.” Secondary emotions include emotions such as sympathy, shame, embarrassment, and guilt. Conceivably, if psychopaths lack the ability to form these somatic-affective associations as a result of being less sensitive to physiological 56 changes, then they may be less likely to experience these secondary emotions. In fact, deficits in these emotions are a defining characteristic of psychopathy. Without these somatic markers, individuals high in psychopathic characteristics may be less inhibited by secondary emotions and consequently more likely to engage in manipulation. For example, white collar crimes such as fraud often take place over an extended period o f time, during which an individual would have several opportunities to assess whether or not they should proceed. An individual low in psychopathic traits may feel emotions such as guilt and shame as a consequence o f unpleasant somatic markers, influencing them to stop; whereas an individual high in psychopathic traits would likely lack the unpleasant somatic markers and subsequent emotions and consequently be uninhibited to proceed. Implications. This finding is consistent with the somatic marker hypothesis, which proposes that bodily (e.g., autonomic) feedback to cortical areas is critical for emotional responding (Damasio, 1994). More specifically, Damasio (1994) suggests that somatic markers are formed through learning by automatically pairing the outcome of particular choices with particular body (somatic) states. These markers can then be used to guide decision-making (Bechara & Damasio, 2005). For example, negative markers would decrease the likelihood that an option is selected and positive markers would increase the likelihood. It has been suggested that somatic markers increase the efficiency of decision­ making by rapidly eliminating undesirable options (Damasio, 1994; Felson & Reiner, 2011). Studies involving the Iowa Gambling Task have found provided evidence in support of this theory. In the task, participants select a card from four decks of cards and receive a monetary outcome after each selection. Two of the decks are conservative, yielding small rewards and small punishments, whereas the other two decks are risky, yielding large 57 rewards and large punishments. In the beginning of the task, participants tend to select more cards from risky decks. However, as the task progresses, they begin to favor the conservative decks and generate skin conductance responses (SCRs) before selecting cards from risky decks (e.g., Bechara, Damasio, Damasio & Lee, 1999). Such anticipatory SCRs are thought to be one o f the somatic markers inhibiting risky decisions. Individuals with amygdala lesions have been found to prefer the risky decks and fail to generate anticipatory SCRs (e.g., Bechara et al., 1999). Similarly, psychopathic individuals demonstrated the same impaired gambling behaviour on the Iowa Gambling Task (van Honk et al., 2002). The finding from the present study that individuals high in psychopathic characteristics are less sensitive to changes in their heart rate is consistent with the notion that psychopaths have difficulty forming and utilizing affective somatic associations. If individuals high in these traits lack somatic-affective associations, these individuals would be unable to make use of the rapid, effective emotion-based decision making that is facilitated by somatic markers. Additionally, it suggests that this difficulty is a result o f decreased sensitivity to interoceptive cues, rather than a general autonomic hyporeactivity. This decreased interoceptive sensitivity or somatic aphasia could provide insight into numerous traits associated with psychopathy, including impulsivity, irresponsibility, impaired decision making, and decreased aversive conditioning. For example, a recent study found that participants with good cardiac perception chose significantly fewer disadvantageous and more advantageous options in the Iowa Gambling Task, demonstrating increased decision making and risk assessment skills (Werner, Jung, Duschek & Schandry, 2009). Additionally, Katkin, Wiens, and Ohman (2001) showed superior classical conditioning in individuals with good heartbeat perception, suggesting better learning and 58 memory performance. These deficits in learning and decision making could predispose individuals high in psychopathic traits to violent, antisocial behaviour. More specifically, because individuals high in psychopathic characteristics may be less sensitive to physiological changes during emotional experience, they may lack the “unpleasant gut feeling” associated with somatic markers. The inability to experience this “gut feeling” may in turn cause them to make riskier decisions and be less responsive to punishment (i.e., aversive conditioning). Together, these riskier decisions and diminished response to punishment could help explain the antisocial behaviour and increased rates of recidivism associated with psychopathy. Third-Person Pain Perception It has been consistently shown that psychopathy is associated with recognition deficits for basic emotions (e.g., Dawel et al., 2012; Wilson, Juodis, & Porter, 2011). Additionally, it is widely believed that psychopathic individuals have a profound empathy deficit, resulting in a lack of regard for others’ pain. However, it has remained unclear whether the lack of empathy characterizing psychopathy is related to a deficit in the recognition of painful expressions. To my knowledge, the study by Caes et al. (2012) was the first and only other study to examine the influence of psychopathic characteristics on sensitivity to pain in others. As previously mentioned, using a vicarious-conditioning paradigm, these researchers found that individuals high in psychopathic characteristics were less accurate in detecting pain in others. However, because they used a vicarious conditioning paradigm, it remained unclear whether their measure of perceptual sensitivity reflected detection of pain or detection of other negative emotional expressions that may have occurred during their paradigm. 59 As shown in Figure 3, individuals in the present study who were high in psychopathic characteristics performed better than chance when discriminating between levels o f pain based on facial expressions o f others. Consequently, they were not completely insensitive to evidence o f pain in others. However, they performed significantly worse than individuals scoring low in psychopathic characteristics. As predicted, findings from this study indicate that individuals high in psychopathic characteristics are significantly less sensitive to the facial expressions of pain in others’. Interestingly, however, psychopathic characteristics were not associated with a response bias. That is, these individuals were no more or less likely to infer pain than individuals low in these traits. It should be noted that the third-person pain task was explicitly designed to be difficult, including only lower levels of pain expressions. This was done because previous studies examining third-person pain perception that included high-intensity pain expressions yielded measures of sensitivity that were thought to be too high to capture the range of individual differences anticipated to relate to psychopathic deficits in the present study (e.g., Prkachin et al., 2004; Prkachin & Rocha, 2010; Wojakiewicz et al., 2013). Additionally, participants were undergraduate students and thus unlikely to score high on psychopathic characteristics. Nevertheless, the results o f the present study replicate and expand the findings from Caes et al. (2012) with significant correlations occurring at every level of discrimination, for both intensity and unpleasantness ratings of pain, across the subscales of the SRP-III. No significant correlations were found for response bias. Taken together, these results suggest that psychopathic characteristics are associated with a true perceptual deficit in the perception of pain expressions rather than a motivational bias. However, these findings do raise the questions o f whether individuals high in psychopathic characteristics would 60 exhibit the same deficit with strong pain expressions and whether these findings generalize to other populations such as criminal psychopaths. Importantly, this deficit in perceptual sensitivity was not related to empathy levels, as measured by the TEQ. Rather, it appears to be directly related to other traits associated with psychopathy, such as callous affect and antisocial behaviour. As previously mentioned, it is commonly believed that psychopathic individuals have a lack of regard for others’ pain. As such, it is a logical finding that a deficit in third-person pain perception is related to the callousness or cold-hearted traits associated with psychopathy, as well as antisocial behaviour. These findings provide evidence that the lack of empathy and violent behaviour characterizing psychopathy may be a consequence of a diminished ability to perceive others’ pain. Implications. These findings are potentially important for numerous reasons. First, they add support to the VIM model o f psychopathy (Blair; 1995) that states that nonverbal communication of distress (e.g., facial displays of fear or sadness) triggers cognitive processes involved in the recognition o f distress by others. This recognition of distress is said to result in empathy, which will inhibit violent behaviour or promote prosocial behaviour. According to Blair (1995), because psychopathic individuals are incapable of recognizing the fearful expression in others, their VIM is never fully activated and thus they lack the cues to inhibit aggression or behave in a prosocial way in the face of signals of submission or distress. Findings from the present study add support for this theory and expand it to include the expression of pain, in addition to fear and sadness. Second, these findings provide insight into the violent, antisocial behaviour and lack of empathy associated with psychopathy. In line with the VIM model, if an individual is 61 unable to accurately perceive an expression of pain, they will be unlikely to engage in prosocial behaviour and be less inhibited about engaging in antisocial behaviour. For example, imagine an individual who is unable to perceive a facial expression o f pain. If this individual encounters someone in pain, it would make sense that the individual would be unable to empathize with the person in pain. Consequently, the individual would be unlikely to engage in helping behaviour. Conversely, this decreased sensitivity to pain expressions could facilitate antisocial behaviour and contribute to the high rate of violent crimes among psychopaths. For example, if the individual was engaging in an activity that hurt another person and was unable to perceive the expression o f pain, that individual would lack cues that may inhibit the violent behaviour. Moreover, failure to identify cues of submissiveness (i.e., pain) could explain why psychopaths have been found to engage in significantly more sadistic violence that nonpsychopaths (Porter, Woodworth, Earle, Drugge & Boer, 2003). That is, they make lack the cues that would ordinarily inhibit an individual from engaging in extreme violence. A perceptual deficit for the expression of pain could be beneficial in some situations. A decreased ability to perceive pain expressions may lead to an attraction to certain career choices and could facilitate performance. For example, an inability to perceive pain may be beneficial for work as a military member, police officer, or interrogator. Alternatively, this deficit could be problematic in careers involving care-giving. For example, in the role of a physician or nurse, an inability to accurately perceive pain could lead to a decreased ability to adequately provide care. Facial expressions have been shown to contribute significantly to individuals’ ratings of others’ pain (Ahles, Coombs, Jensen, Stukel, Maurer & Keefe, 1990; Hale & Hadjistavropoulous, 1997). In some cases, as with nonverbal patients, facial 62 expressions offer the best means for accurate assessment of pain (Williams, 2002). In an investigation of the undertreatment of acute pain in emergency departments, it was concluded that inadequate pain management was significantly associated with poor assessment o f pain, and when the assessment of pain improved time delays in treatment were reduced and more patients with moderate pain received analgesics (Stalnikowicz, Mahamid, Kaspi, & Brezis, 2005). Practical Applications Identification. There is well-established link between psychopathy and criminal behaviour. In fact, it has been suggested that psychopathy may be the single best predictor of future violence and recidivism (Salekin, Rogers, & Sewell, 1996; Serin & Amos, 1995), estimating to cost the US criminal justice system $460 billion per year (Kiehl & Hoffman, 2011). Early identification of psychopathy could aid in the prevention of costly criminal careers (Vaughn, Howard, & DeLisi, 2008). Moreover, due to the relative ineffectiveness of treatment among adult psychopaths, it has been argued that the assessment and study of child and adolescent psychopathy could hold the key to its treatment (Lynam, Caspi, Moffitt, Loeber & Stouthamer-Loeber, 2007). Recent findings suggest that psychopathy is relatively stable from age thirteen to age twenty-four (Lynam et al., 2007). Additionally, psychopathic offenders have also been found to begin offending at an earlier age than other offenders (Blackburn & Coid, 1998; Smith & Newman, 1990; Vaughn et al., 2008). Specifically, it has been found that high psychopathic youths (i.e., those scoring one standard deviation above the mean on combined psychopathy measures) were approximately 300% more likely to begin offending earlier compared to youths scoring one standard deviation below the mean (Vaughn et al., 2008). 63 Consequently, a number of self-report measures of psychopathic characteristics have been developed that are based on a dimensional model and intended for use in non­ incarcerated populations, as well as in children and adolescents (e.g., Frick & Hare, 2001; Levenson et al., 1995; Lilienfeld & Widows, 2005; Paulhus et al., 2012). Although selfreport measures have many advantages, they also have potential disadvantages. For example, because psychopathic individuals are prone to deception and manipulation the ability o f selfreport measures to detect psychopathy may be somewhat compromised (Lilienfeld, 1994; Poythress, Lilienfeld, Skeem, Douglas, Edens, Epstein & Patrick, 2010). Additionally, it has been suggested that it is paradoxical to ask individuals to report on the frequency of emotions that they have rarely, if ever, experienced and may not fully comprehend (Lilienfeld, 1994; Poythress et al., 2010). The findings from this study may offer an alternative method or supplement to selfreport measures for the detection of psychopathy. For example, if, as suggested by the findings of this study, psychopaths have a perceptual deficit in the recognition of pain expressions, a task such as the one employed in this study could potentially prove beneficial in the identification of psychopathic characteristics. A perceptual-sensitivity task could aid in reducing the issues of deception and manipulation and would not require the individual to have insight into their emotional deficits. Additionally, this task may be useful as a tool for screening individuals high in psychopathic traits out of, or even into, certain careers. For example, as mentioned, career positions such as physician or nurse may require the accurate detection of pain expressions. In these care-giving careers, insensitivity to facial expressions of pain could prove harmful in terms of inadequate treatment or delays. As such, a task such as that used in this study to 64 examine third-person pain perception may serve as a valuable tool for the screening of these traits and deficits associated with psychopathy. Treatm ent. It is known that psychopaths represent approximately 25% of the prison population (Babiak & Hare, 2006; Hare, 2003). Additionally, psychopaths are more likely to reoffend, and recidivate violently (Serin & Amos, 1995). Based on the high rates of criminal behaviour associated with psychopathy, it is clear that there is a pressing need for treatment. Unfortunately, to date, therapeutic interventions and rehabilitation efforts with psychopaths have shown to be largely ineffective, and occasionally counterproductive (e.g, Ogloff, Wong, & Greenwood, 1990; Rice, Harris & Cormier, 1992; Richards, Casey, & Lucente). Findings from the present study could provide direction for more effective treatments of psychopathy. One reason that treatment efforts may currently be ineffective is that the mechanisms underlying the association between psychopathy and lack o f empathy have remained unclear and thus it is unknown where or how to direct treatment. For example, do psychopaths lack empathy because they are unable to feel pain, unable to detect pain, or because they simply do not care about others’ pain? Findings from this study suggest that individuals high in psychopathic characteristics respond similarly to those low in psychopathic characteristics when in pain, both subjectively and physically. Additionally, individuals high in psychopathic behaviour did not exhibit a motivational bias in rating others’ pain. Rather, individuals high in these traits exhibited a decreased ability to accurately identify their own somatic sensations and a decreased perceptual sensitivity to expressions of pain. As stated, both of these deficits could play a role in the lack of empathy and antisocial behaviour seen in psychopathy. The identification o f these deficits could prove beneficial in guiding treatment. The perception of somatic states or interoceptive awareness has been 65 considered essential for emotional processing (Damasio, 1994). Findings from a recent study (Herbert, Herbert, Pollatos, Weimer, Enck, Sauer & Zipfel, 2012) suggest that it possible to improve sensitization of somatic states. Specifically, researchers found that short-term fasting was associated with an improvement in perceiving one’s cardiac activity. Additionally, it has been determined that individuals with schizophrenia are impaired in overall emotional recognition, particularly fear and disgust (e.g., Kohler et al., 2003). Researchers have found that briefly exposing chronic schizophrenia patients to a simple emotion-training program significantly improved their ability to recognize facial emotional expressions (Silver, Goodman, Knoll & Isakov, 2004). Increasing autonomic awareness and recognition of pain expressions may be beneficial in reducing the emotional deficits characterizing psychopathy. F uture Directions Several suggestions for future research arise from this study. Firstly, although evidence has now been found for somatic aphasia in both anxiety-inducing and pain-inducing situations, it remains unclear whether this autonomic-emotion mismatch generalizes to emotional experiences with positive valence. Secondly, in both this study and the study by Caes et al., (2012), the influence of psychopathic characteristics on third-person pain perception was examined in undergraduate students. Future research should investigate whether the diminished sensitivity to others’ pain extends to high scoring, criminal psychopaths. Moreover, future studies should examine whether these deficits mediate the antisocial behaviour and lack of empathy associated with psychopathy. Additionally, although findings from this study suggest that psychopathic traits are associated with a deficit in the sensitivity to others’ pain, psychopaths appear to be sensitive to some socially relevant information as manipulation is a key component o f psychopathy 66 (Book, Quinsey & Langford, 2007). Consequently, while those high in psychopathic characteristics may be less sensitive to cues that evoke empathy, they may be more sensitive to cues that indicate exploitability. However, research in this area is limited and contradictory. While psychopathy has been associated with a deficit in the recognition of fear expressions (Blair et al., 2004), other research suggests psychopathic characteristics are associated with an increased ability to identify fear and assertiveness in others (Book et al., 2007). As with the studies investigating pain perception, methodological difficulties (i.e., employing techniques that confound perceptual sensitivity with response bias) may be responsible for this inconsistency. Future studies should investigate the influence of psychopathic characteristics on the perception of others’ social distress using signal detection methodology. If, as hypothesized, psychopaths show increased sensitivity to others’ anxiety this could signify enhanced sensitivity to signs of exploitability. Taken together, these findings would suggest a “double whammy” effect, indicating that individuals high in psychopathic characteristics are uninhibited predators, seeking advantage on those who provide evidence of vulnerability. These findings could provide insight into the violent behaviour and manipulation associated with psychopathy, as well as elucidate characteristics that facilitate social predation, conceivably guiding intervention for potential victims. Strengths and Limitations This study had several strengths and limitations that should be considered when interpreting the results. First, a significant strength of this study is that pain perception was examined directly. The few studies that have examined the perception of pain in psychopathy have done so using fear-conditioning paradigms. As such, it is difficult to determine whether the effects observed in these studies are directly related to pain or other emotions such as fear 67 or anxiety. Furthermore, there is strong evidence to suggest that fear-conditioning paradigms can have a pain supressing effect. Evidence from numerous animal studies indicates that exposure to conditioned and unconditioned fear stimuli can produce subsequent decreases in pain reactivity or hypoalgesia (e.g., Bolles & Fanselow, 1980; Hemstetter, 1992). This effect has also been observed in humans. Specifically, through the use of conditioning paradigms with fear-inducing shocks, researchers have shown that conditioned fear induces hypoalgesia on both finger-withdrawal and VAS pain rating tests to a radiant heat stimulus (Rhudy, Grimes & Meagher, 2004; Rhudy & Meagher, 2002). These findings suggest that pain thresholds can be increased by conditioned fear. As such, the studies examining the influence of psychopathic characteristics on pain tolerance and threshold may be confounded by fear. Given that psychopathy has been associated with a diminished fear response, individuals high in these traits would conceivably not experience a fear-induced hypoalgesia effects. As such, comparing the pain reactivity of psychopaths and nonpsychopaths using conditioning paradigms may be biased. Instead of using conditioning paradigms, this study directly examined the influence of psychopathic characteristics on both first-person and third-person pain perception. By doing so, the methodology allowed for the independent examination o f perceptual sensitivity and response bias through the use of magnitude estimation procedures and signal detection analysis. Distinguishing between these two parameters of perception (i.e., pain sensitivity and response bias) allows for deeper insight into the emotional deficits associated with psychopathy. A possible limitation o f this study is that psychopathic characteristics were examined in a sample of undergraduate students. The use of undergraduate students may account for 68 the relatively weak statistical effects observed. Additionally, it is possible that these findings may not generalize to other populations such as high scoring criminal psychopaths. However, as previously mentioned, university students with psychopathic traits have been found to show similar emotional and cognitive deficits to incarcerated psychopaths, including response modulation deficits, autonomic hyporeactivity, and risky decision making (e.g., Osumi et al., 2007; Mahmut, Homewood & Stevenson, 2008; Gao & Raine, 2010). Additionally, the fact that consistent effects were found in a relatively advantaged population may suggest that the deficits in pain perception found in this study are indicative of true differences associated with psychopathy and may be even greater in clinical populations. Conclusion Overall, findings from this study provide evidence that suggests psychopathic characteristics influence the perception of pain in oneself and others. Although psychopathic characteristics were not found to be related to lower subjective ratings of pain or reduced physiological activity during pain, psychopathic characteristics were found to be associated with important psychophysiologic differences during the experience o f pain. Specifically, high levels of psychopathic characteristics were associated with a mismatch between individuals’ subjective ratings of pain and physiological activity. Additionally, results of this study suggest that psychopathic characteristics are associated with decreased perceptual sensitivity to others’ pain. Specifically, individuals high in psychopathic characteristics were found to have a decreased ability to accurately perceive facial expressions of pain in others. 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Ethnicity: □ Caucasian/White □ Latino/Hispanic □ Middle Eastern □ First Nations (Aboriginal/Metis) □ Multiple ethnicity □ African □ Caribbean □ South Asian □ East Asian □ Other 7. Handedness: □ Right □ Left □ Both (ambidextrous) 81 Appendix B Self-Report Psychopathy Scale III Please rate the degree to which you agree with the following statements about you. You can be honest because your name will be detached from the answers as soon as they are submitted. 1 2 3 4 5 Disagree Strongly Disagree Neutral Agree Agree Strongly 1. I’m a rebellious person. 2. I’m more tough-minded than other people. 3. I think I could "beat" a lie detector. 4. I have taken illegal drugs (e.g., marijuana, ecstasy). 5. I have never been involved in delinquent gang activity. 6. I have never stolen a truck, car or motorcycle. 7. Most people are wimps. 8. I purposely flatter people to get them on my side. 9. I’ve often done something dangerous just for the thrill of it. 10.1 have tricked someone into giving me money. 11. It tortures me to see an injured animal. 12.1 have assaulted a law enforcement official or social worker. 13.1 have pretended to be someone else in order to get something. 14.1 always plan out my weekly activities. 15.1 like to see fist-fights. 16. I’m not tricky or sly. 17. I’d be good at a dangerous job because I make fast decisions. 18.1 have never tried to force someone to have sex. 19. My friends would say that I am a warm person. 2 0 .1 would get a kick out of ‘scamming’ someone. 21.1 have never attacked someone with the idea of injuring them. 2 2 .1 never miss appointments. 2 3 .1 avoid horror movies. 2 4 .1 trust other people to be honest. 2 5 .1 hate high speed driving. 2 6 .1 feel so sorry when I see a homeless person. 27. It's fun to see how far you can push people before they get upset. 2 8 .1 enjoy doing wild things. 2 9 .1 have broken into a building or vehicle in order to steal something or vandalize. 3 0 .1 don’t bother to keep in touch with my family any more. 31.1 find it difficult to manipulate people. 3 2 .1 rarely follow the rules. 82 3 3 .1 never cry at movies. 3 4 .1 have never been arrested. 35. You should take advantage of other people before they do it to you. 3 6 .1 don’t enjoy gambling for real money. 37. People sometimes say that I’m cold-hearted. 38. People can usually tell if I am lying. 3 9 .1 like to have sex with people I barely know. 4 0 .1 love violent sports and movies. 41. Sometimes you have to pretend you like people to get something out of them. 4 2 .1 am an impulsive person. 4 3 .1 have taken hard drugs (e.g., heroin, cocaine). 44. I'm a soft-hearted person. 4 5 .1 can talk people into anything. 4 6 .1 never shoplifted from a store. 4 7 .1 don’t enjoy taking risks. 48. People are too sensitive when I tell them the truth about themselves. 4 9 .1 was convicted of a serious crime. 50. Most people tell lies everyday. 51.1 keep getting in trouble for the same things over and over. 52. Every now and then I carry a weapon (knife or gun) for protection. 53. People cry way too much at funerals. 54. You can get what you want by telling people what they want to hear. 55.1 easily get bored. 5 6 .1 never feel guilty over hurting others. 5 7 .1 have threatened people into giving me money, clothes, or makeup. 58. A lot of people are “suckers” and can easily be fooled. 59. I admit that I often “mouth o ff’ without thinking. 6 0 .1 sometimes dump friends that I don’t need any more. 61.1 would never step on others to get what I want. 6 2 .1 have close friends who served time in prison. 6 3 .1 purposely tried to hit someone with the vehicle I was driving. 6 4 .1 have violated my parole from prison. 83 Norms for offender, student, and community samples IPM CA ELS ASB Overall Offenders Wisconsin 2.80 2.75 3.31 3.00 2.97 College students Texas & UBC 2.38 2.31 2.56 1.56 2.20 Community Eugene-Springfield 1.94 1.88 1.94 1.25 1.75 Note. Entries are item means on 5-point scales. Student and community samples have equal number of male and female respondents. Offenders are all male. Sample sizes range from 300 to 1500. Overall alpha reliabilities from the student sample were: IPM (.81) CA (.79) ELS(.74) ASB (.82) Overall SRP (.81). 84 Appendix C Toronto Empathy Questionnaire Below is a list of statements. Please read each statement carefully and rate how frequently you feel or act in the manner described. Circle your answer on the response form. There are no right or wrong answers or trick questions. Please answer each question as honestly as you can. Never Rarely Sometimes Often Always 1. When someone else is feeling excited, I tend to get excited too 0 2. Other people's misfortunes do not disturb me a great deal 0 3. It upsets me to see someone being treated disrespectfully 0 4. I remain unaffected when someone close to me is happy 0 5. I enjoy making other people feel better 0 4 6. I have tender, concerned feelings for people less fortunate than me 0 4 7. When a friend starts to talk about his\her problems, I try to steer the conversation towards something else 0 8. I can tell when others are sad even when they do not say anything 0 9. I find that I am "in tune" with other people's moods 0 2 4 10. I do not feel sympathy for people who cause their own serious illnesses 0 2 4 11. I become irritated when someone cries 0 2 4 12. I am not really interested in how other people feel 0 2 4 13. I get a strong urge to help when I see someone who is upset 0 2 4 14. When I see someone being treated unfairly, I do not feel very much pity for them 0 15. I find it silly for people to cry out of happiness 0 4 16. When I see someone being taken advantage of, I feel kind of protective towards him\her 0 4 85 Appendix D Task Instructions First-Person Pain Task “During this task, I am going to ask you to put your left hand into this cold water bath. Exposure to cold water is harmless; however, it can be associated with some discomfort or pain, which is absolutely normal and has no further consequences. While your hand is in the water, I would like you to make a set of two pain ratings every fifteen seconds. These ratings will be of two different components of pain, intensity and unpleasantness. The first is easy to distinguish - it is how much the cold water physically hurts your hand and arm. The second type o f pain is emotional; it is how much the pain bothers or annoys you. The distinction between these two aspects of pain might be made clearer if you think of listening to music on a radio. As the volume of the music increases, I can ask you how loud it sounds or how unpleasant it is to hear. The intensity of pain is like loudness. The pleasantness or unpleasantness of the music depends on how much you like or dislike the music. The unpleasantness o f pain depends on how much you dislike the feeling. Here are examples of each scale (show posters). The bottom range of the first scale represents “no pain at all,” while the top range represents “worst pain imaginable”. To manipulate this scale, you click on the spot on the scale that you feel best represents your sensory pain. The bottom range of the second scale represents “not at all” unpleasant, while the top range represents “the most unpleasant feeling.” You will use this scale in the same way as the first one. Each scale will remain on the screen for ten seconds, or until you make your rating. A “ding” will sound every fifteen seconds to remind you to make a new set of ratings. The task will continue for three minutes. You should try to keep your hand and arm in as long as you can; however, if you feel you cannot endure the full three minutes, you may withdraw your hand and terminate the experiment. Using this monitor, I will observe your hand from the adjoining room. The monitor will transmit video and audio to me, so that I may let you know when to start the task, and you may let me know when you’ve finished. The monitor transmits audio as well as video of your arm in real time; it is not making any recordings. I’m going to go to the other room to calibrate the psychophysiological recording equipment. Please remain still, with your arm resting on the armrest, until three minutes have passed and you hear me say 86 “start.” Then, put your hand in the water, and click anywhere on the screen to begin the task. It is very important that you try to remain as still as possible during the task, as any body movements will interfere with the psychophysiological recording equipment. When the task is over, say “stop,” and we will continue to the next part of the experiment. Do you have any questions?” Third-Person Pain Task “During this task, I’ll ask you to view a video consisting of 60 clips of other people in varying amounts o f pain. Following each clip, you will make a set of pain ratings. One rating will be o f pain intensity, and the other will be of pain unpleasantness. The first is easy to distinguish - it is how much you believe the pain physically hurts the person in the clip. The second type of pain is emotional; it is how much you think the pain bothers or annoys the person in the clip. Here are examples o f each scale (show posters). The bottom range of the first scale represents “no pain at all,” while the top range represents “worst pain imaginable”. To manipulate this scale, you click on the spot on the scale that you feel best represents the sensory pain of the person in the clip. The bottom range of the second scale represents “not at all” unpleasant, while the top range represents “the most unpleasant feeling.” You will use this scale in the same way as the first one.” 87