Discourse of a Mind
Relationship Between the Two-Process Theory of Psychopathy,
P3 and Stimulus Modality
Melanie Tremblay, Julia Kam, & Scott R. Carlson
INTRODUCTION
• 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 attention1. Recent theories suggest that these characteristics are
potentially independent dimensions of psychopathic personality2.
• 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 dependence3.
• 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 functioning4. 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 modality5.
Researchers suggested that visual P3 is associated more strongly with externalizing risk6.
Department of Psychology, University of British Columbia,
Vancouver
RESULTS
• 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 TraitFearlessness 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.
• 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 studies7, 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 P34. 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.
• No one has yet examined whether or not stimulus modality influences the relationship
between P3 amplitude and psychopathic trait dimensions.
• Consumption of different substances such as caffeine, nicotine and alcohol7, in addition to
an early-onset substance use disorder2,8 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.
METHOD
• 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.
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 SelfCentered Impulsivity, respectively). Participants also responded to questionnaires enquiring
on their substance use habits such as caffeine and alcohol consumption, and drug use.
PURPOSE
• 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.
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.
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)
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