1. INTRODUCTION PURPOSE METHOD RESULTS DISCUSSION “Their acts result not from a deranged mind but from a cold, calculating rationality combined with a chilling inability to treat others as thinking, feeling human beings” – Robert HARE (1999) Melanie Tremblay, Julia Kam, & Scott R. Carlson Department of Psychology, University of British Columbia, Vancouver Psychopathy features personality and interpersonal characteristics such as deceit, manipulation, and associated lack of empathy and ignorance of the feelings and suffering of others. Psychopathic personality is also associated with recklessness, impulsivity and sensation seeking that may be related to limitations of executive control of behaviours, response inhibition and attention 1. Recent theories suggest that these characteristics are potentially independent dimensions of psychopathic personality 2. Recently, Patrick and Bernat (2009) proposed the Two-Process Theory suggesting that psychopathy includes two separate dimensions; Trait Fearlessness, associated with the affective and interpersonal aspects, and Externalizing Vulnerability relating to the characteristic impulsivity, poor inhibition capacities and higher level of aggressiveness also seen in individuals with drug and alcohol dependence 3. The P3 Event-Related Potential (ERP) component reflects cognitive processes such as executive attention, working memory, and inhibition related to executive functions. Evidence suggests that the two dimensions of psychopathy could have opposite underlying cognitive mechanisms with Externalizing Vulnerability associated with reduced P3 and Trait Fearlessness associated with enhanced executive cognitive functioning 4. Carlson et al., (2009) found a specific relationship between a reduction in P3 amplitude and the externalizing dimension of psychopathy. The authors also found the reverse results with an increase in P3 amplitude associated with the Trait Fearlessness dimension. Externalizing characteristics could also be related to P3 differently as a function of stimulus modality 5. Researchers suggested that visual P3 is associated more strongly with externalizing risk 6. No one has yet examined whether or not stimulus modality influences the relationship between P3 amplitude and psychopathic trait dimensions. Discourse of a Mind The findings of this study aimed at increasing understanding of the phenomenon and etiology surrounding psychopathy by suggesting underlying neural functions associated with the disorder. We tried to determine if visual P3 amplitude was more strongly associated with the Externalizing Vulnerability dimension. Establishing differences in P3 in psychopathic individuals could give insight for possible genetic markers for psychopathy, but also other disorders such as internalizing and anxiety related disorders. REFERENCES 1. Morgan, A. B., & Lilienfeld, S. O. (2000). A meta-analytic review of the relation between antisocial behavior and neuropsychological measures of executive function. Clinical Psychology Review, 20, 113–136. doi: 10.1016/S0272-7358(98)00096-8 2. Patrick, C. J. & Bernat, E. M. (2009). Neurobiology of psychopathy: A two-process theory. In G. G. Berntson & J. T. Cacioppo (Eds.), Handbook of neuroscience for the behavioural sciences. New-York: John Wiley & Sons. 3. Krueger, R. F., Hicks, B., Patrick, C. J., Carlson, S. R., Iacono, W. G., & McGue, M. K. (2002). Etiologic connections among substance dependence, antisocial behavior, and personality: Modeling the externalizing spectrum. Journal of Abnormal Psychology, 111, 411-424. doi: 10.1037//0021-843X.111.3.411 4. Selbom, M., & Verona, E. (2007). Neuropsychological correlates of psychopathic traits in a non-incarcerated sample. Journal of Research in Personality, 41, 276–294. doi: 10.1016/j.jrp.2006.04.001 5. Reese, C. & Polich, J. (2003). Alcoholism risk and the P300 event-related brain potential: Modality, task, and gender effects. Brain and Cognition, 53, 46-57. doi: 10.1016/S0278-2626(03)00202-1 6. Polich, J., Pollock, V. E. & Bloom, F. E. (1994). Meta-Analysis of P300 amplitude from males at risk for alcoholism. Psychological Bulletin, 115, 55-73. doi: 10.1037/0033-2909.115.1.55 7. Carlson, S. R., Thai, S. & McLarnon, M. E. (2009). Visual P3 amplitude and self-reported psychopathic personality traits: Frontal reduction is associated with self-centered impulsivity. Psychophysiology, 46, 100-113. doi: 10.1111/j.1469-8986.2008.00756.x 8. Benning, S. D., Patrick, C. J., Hicks, B. M., Blonigen, D. M., & Krueger, R. F. (2003). Factor structure of the Psychopathic Personality Inventory: Validity and implications for clinical assessment. Psychological Assessment, 15, 340-350. doi: 10.1037/1040-3590.15.3.340 This study found a moderate correlation between the two dimensions of psychopathy; Externalizing Vulnerability and Trait-Fearlessness (r =.43, p =.008) such that individuals who scored high on one dimension also scores high on the other, and vice versa. We did not find a significantly stronger association between reduction in P3 amplitude and the Externalizing Vulnerability dimension of Psychopathy, compared to the Trait- Fearlessness dimension. Contrary to our prediction, we found a non significant but small positive correlation between the Externalizing factor and P3 amplitude. Finally, we found no relationship between either dimensions of the Two Process Theory of Psychopathy and task modality, or between task modality and P3 amplitude at different scalp locations. Table 1 demonstrates our results correlations between task modality at specific scalp locations and the two dimensions of psychopathic personality. Participants The data were collected from 30 right handed undergraduate students between the age of 17 and 25 recruited from a university research pool. Measures Experimenters used the Psychopathic Personality Inventory-Revised (PPI-R) in order to assess psychopathic traits in the sample of participants. Trait Fearlessness and Externalizing Vulnerability are tapped by PPI-R factor scores (also known as Fearless Dominance and Self- Centered Impulsivity, respectively). Participants also responded to questionnaires enquiring on their substance use habits such as caffeine and alcohol consumption, and drug use. Procedure and Apparatus P3 Assessment. Participants executed two consecutive oddball tasks presented in two different modalities; visual and auditory, provided in a random order across individuals established by counterbalancing. Participants pressed one of two buttons on a response box that were either on the same side (easy condition) or on the opposite side (hard condition) of a stimulus as fast and accurately as possible. Each task required about 15 minutes to complete. Visual task. A circle with a nose pointing up with either a right or left ear constituted the easy condition and required a response on the corresponding side of the presentation of the ear. A nose pointing down constituted the hard condition and required a response opposite to the side from which the ear was presented. A plain circle did not require a response. Auditory task. A high frequency tone of 2400Hz presented to only one ear constituted the easy condition and required a response on the corresponding side of the ear in which the tone was presented. A low frequency tone of 800Hz presented to only one ear constituted the hard condition and required a response on the opposite side of the ear in which the tone was presented. A medium frequency tone of 1600Hz presented to both ears did not require a response. Psychopathy is a complex phenomenon. This research project attempted to reconcile previous inconsistency in results that studied P3 amplitude and its relationship with psychopathic traits by looking at specific associations with the two dimensions of psychopathy assessed by the Psychopathic Personality Inventory Revised (PPI-R). In contrast with previous studies 7, we did not find a relationship between P3 amplitude and the two dimension of psychopathy proposed by the Two-Process model. Our small sample could account for our failure to replicate previous studies. It would be logical to observe an inverse relationship in P3 amplitude between the two dimensions of psychopathy since Externalizing Vulnerability is relates to a deficit in executive cognitive functioning associated with reduced P3, whereas Trait Fearlessness relates to an enhanced executive cognitive functioning associated with increased P3 4. In addition, undergraduate students may not possess strong externalizing traits and antisocial tendencies as would be expected in a convicted inmate population. Students who score high on the PPI-R could have developed self-discipline and cognitive capacities that compensate for a reduction in executive functioning that would have resulted in reduced P3 amplitude. This was the first study to look at modality as a moderator of the relationship between P3 amplitude and the two dimensions of psychopathy. It is possible that task modality does not significantly affect underlying cognitive processes involved in decision making necessary for simple oddball visual and auditory tasks. However, stimulus demand such as the simplicity and artificiality of the tasks could also account for our failure to find significant results. Consumption of different substances such as caffeine, nicotine and alcohol 7, in addition to an early-onset substance use disorder 2,8 could also alter brain activity and act as potential confounds by being associated with the Externalizing Vulnerability dimension of the PPI-R, possibly accounting for our lack of outcomes. Despite our lack of significant results, evidences from past studies suggest that differences in brain mechanism and related P3 amplitude exist not only between individuals with psychopathic traits and non-psychopathic subjects, but also between the two dimensions of psychopathy. Relationship Between the Two-Process Theory of Psychopathy, P3 and Stimulus Modality