The results of the current study were generally consistent with our hypotheses in that psychopathic personality traits linked to primary and secondary psychopathy were differentially related to abnormal perceptual selection and cognitive control, respectively. In particular, traits typically associated with primary psychopathy (i.e., PPI-CU) were associated with reduced distractor processing at a lower level of perceptual load than low levels of these traits. This finding suggests that individuals with primary psychopathic traits may have diminished early perceptual processing capabilities, which may explain their tendency to screen out environmental information that is irrelevant to goal attainment, such as distress cues that engender empathy or threatening consequences that deter antisocial behavior. Conversely, high levels of secondary psychopathic traits (i.e., PPI-II) were related to both less response interference from distractors under low working memory load and greater response interference from distractors under high working memory load. Individuals with these traits may respond impulsively and have trouble maintaining cognitive control in complex situations, which could explain their risk-taking tendencies and problems with frustration and anger regulation.
On the Perceptual Load Task, high scores on PPI-CU were related to diminished distractor processing at a less perceptually demanding load (i.e., perceptual load 4) than participants as a whole who continued to show interference from the distractors until the most perceptually demanding condition (i.e., perceptual load 6) (cf. Huang-Pollock et al., 2002
; Maylor & Lavie, 1998
). Interestingly, this is the first study to identify individual differences in distractor processing under high
levels of perceptual load, which challenges research that suggests individual differences may only be important for determining distractibility at low levels of perceptual load (Forster & Lavie, 2007
). Although the performance by the high PPI-CU scorers may seem adaptive and not a “deficit”, cognitive researchers have observed similar findings among young children and older adults and have attributed their reduced processing of distractors at low levels of perceptual load to underdeveloped attentional capacity for perceptual selection and the deleterious effects of aging on processing capacity, respectively (Huang-Pollock et al., 2002
; Maylor & Lavie, 1998
). Individuals with primary psychopathic personality traits seem to exhibit a similar decrease in perceptual processing capacity.
This finding may be a result of the affective poverty (e.g., low neuroticism) that is central to the disorder. From a developmental perspective, individuals with low levels of anxiety may allocate relatively fewer attentional resources to monitoring their environment for threatening stimuli, which in turn may influence their capacity to perceive peripheral information overtime. Thus, a long-term consequence of psychopathic individual's tendency to devote less attentional resources to processing contextual information may be overall reduced perceptual capacity relative to individuals who are motivated by anxiety or fear to regularly monitor peripheral stimuli for threatening cues. In support of this contention, deficient contingency monitoring and peripheral information processing has been repeatedly observed in incarcerated individuals with primary psychopathic traits (Jutai & Hare, 1983
; Newman, Patterson, & Kosson, 1987
Although the neuroanatomical basis for this deficit is currently unknown, the brain mechanisms implicated in both the emotion- and attention-based models of psychopathy are plausible contributors to the reduced perceptual capacity observed in this study. More specifically, the capacity of the frontoparietal attention network (i.e., right prefrontal cortex, frontal eye fields, anterior cingulate, parietal cortex) engaged by the perceptual load task may be reduced in individuals high on primary psychopathic traits as a consequence of chronic hypoactivation in the amygdala and thus reduced reciprocal connections with cortical regions that modulate attention, such as the prefrontal cortex. Given this theoretical model, it is interesting to note that we observed differences in attentional functioning on a task that did not involve affective stimuli, suggesting that if amygdala deficits/ fearlessness can account for performance on this task (as some emotion-based models would assume), it may be due to the long-term outcome of these deficits on attentional processing. Alternatively, the attentional abnormality observed in this study may reflect deficits in septohippocampal system functioning or the combined effect of amygdala and septohippocampal system dysfunction, given their reciprocal interconnections. Based on Newman's (1998)
theory, the reduced peripheral processing observed among those high on primary psychopathic traits could be interpreted as a consequence of poor integration of bottom-up inputs (i.e., task-irrelevant distractors) coming from visual areas into an established top-down attentional set (i.e., focusing only on targets). Since this model is not based primarily on an emotion deficit, it provides an explanation for the abnormal selective attention observed in a task with relatively neutral stimuli (perceptual load task) that does not rely on the long-term of effects of limbic system dysfunction. However, it does not preclude the possibility of a more complex interaction between deficits in the amygdala and septohippocampal system. More research is needed to clarify the neural substrates that govern the development of attenuated attentional capacity in primary psychopathy, including work that uses psychophysiological and neural imaging techniques to determine whether the abnormalities in perceptual processing observed in this study via behavioral indices can be detected at earlier stages of processing, such as sensory brain potentials.
Analysis of the Cognitive Control Task revealed a selective impairment under the high working memory load for individuals elevated on certain PPI-II subscales, particularly Blame Externalization. These findings suggest that taxing working memory capacity differentially affects the ability of individuals with high levels of alienation and hostility to control the effects of incompatible distractors on their behavioral responses. Diminished cognitive control may contribute to the chronic irresponsibility, substance use, and emotional dysregulation observed in individuals with high levels of these traits. It should be noted that the Blame Externalization subscale of the PPI is conceptually distinct from what is assessed in the PCL-R item “lack of remorse”. The PCL-R assesses the psychopath's inability to take responsibility for criminal actions, whereas PPI Blame Externalization assesses feelings of distrust and resentment and correlates with negative affect traits such as alienation (r
= .70) and aggression (r
= .34) (Benning et al., 2003
). Research has found associations between low agreeableness (i.e., antagonism) similar to Blame Externalization and deficient prefrontal activation using hemodynamic measures (Haas, Omura, Constable, & Canli, 2007
A subset of PPI-II traits, especially those measuring impulsivity and sensation-seeking (Impulsive Nonconformity and Carefree Nonplanfulness), were differentially related to faster responding (but not error rate) under low working memory load. This finding suggests that impulsivity may be advantageous in fairly simple tasks, with no gross cognitive abnormalities observed among persons with impulsive and nonplanful traits. However, most real-life endeavors involve substantial complexity and dual-tasking, which may explain why these traits were not related to rapid responding under high working memory loads (i.e., individuals high on these traits needed to slow their responding under high cognitive load in order to respond correctly). Given the differential relationships of the social deviance factor subscales of the PPI with performance on the cognitive control task, it may be important in future research on cognitive functioning in psychopathy to examine these personality traits both in isolation and as an aggregate factor. Indeed, our findings for PPI-II are consistent with work in the personality psychology literature, which suggests that narrowly construed facets show more predictive validity than broader dimensions (Paunonen, Haddock, Forsterling, & Keinonen, 2003
). It is important to note, however, that the follow-up analyses with the individual PPI-II subscales on the Cognitive Control Task were exploratory in nature and conducted in an attempt to understand the unexpected association between PPI-II with RT interference under low working memory load. Thus, the findings with the individual subscales should be interpreted with caution until further research is conducted.
Strengths, Weaknesses, and Future Directions
This study has several strengths. One contribution is its ability to demonstrate hypothesized relationships between a widely-used self-report measure of psychopathy and mechanisms of attention, research that is currently lacking. Secondly, we attempted to advance current cognitive models of psychopathy by adopting an up-to-date theory on mechanisms of selective attention developed in the cognitive psychology literature. Importantly, this study is one of the few to examine individual difference moderators of the perceptual load theory advanced by Lavie and colleagues (1995)
. Additionally, we used a well-validated assessment instrument to examine the multidimensional nature of psychopathic traits, which allowed us to investigate the combined cognitive effects that contribute to the manifestation and development of the disorder.
In addition to these strengths, the current study also has limitations. One potential concern is how closely the Perceptual Load task employed resembles cognitive demands that arise in real world situations. In support of the ecological validity of this task, Forster and Lavie (2007)
have demonstrated an association between distractibility on a variant of the perceptual load task in a laboratory setting and distractability in everyday life. Higher interference in response to distractors has been linked to attentional deficits that occur in the natural environment, which suggests that the decreased interference from distractors under high perceptual load observed in high PPI-CU scorers is also representative of how these individuals process information in everyday life. Psychopathic individuals' tendency to myopically focus on obtaining a goal or reward regardless of contradicting peripheral information (e.g., high probability of arrest, distress cues that engender empathy) is an example of how this type of abnormal selective attention may relate to psychopathic behavior as it occurs in the real world.
Secondly, although we recruited from both the general community and the college campus, participants were mostly college students who likely had relatively intact cognitive functions. Despite the potentially restricted range of our sample, we still detected differences on the tasks that were consistent with research in incarcerated individuals (Hiatt et al., 2004
; Vitale et al., 2007
). Additional replication in incarcerated or forensic samples is still needed to ascertain how these attentional mechanisms operate in more severe manifestations of the psychopathic syndrome. Furthermore, the magnitude of the relationships we found between the psychopathy factors and the cognitive tasks were relatively small (r
s ~ .25), which limits the implications of these findings. However, the effect sizes obtained are comparable to those reported in other investigations of affective or cognitive abnormalities in forensic samples (e.g., Benning, Patrick, & Iacono, 2005
; Bernat, Hall, Steffen, & Patrick, 2007
). We also did not include female participants, which further limits the generalizability of our findings to non-incarcerated men. Prior studies on the generalizability of laboratory findings to psychopathic females has been equivocal, with some cognitive abnormalities observed with males replicating among females (e.g., abnormal selective attention; Vitale et al., 2007
) while others do not (response perseveration; Vitale & Newman, 2001
). Importantly, abnormal selective attention has been demonstrated among both male and female psychopathic offenders (Hiatt et al., 2004
and Vitale et al., 2007
, respectively), which increases the likelihood that our findings generalize to females.
Given that the community and student samples were compensated differently (money versus course credit, respectively) it should be considered that the form of compensation each received may have influenced task performance (e.g., increased or decreased motivation), though the compensation was non-contingent on performance. Furthermore, the stimuli in this study were limited to the visual modality, leaving open the possibility that our findings are modality specific. In relation to psychopathy, there is no theoretical reason to expect the results would change if the stimuli were presented aurally, and Jutai & Hare (1983)
found a similar effect (reduced processing of peripheral stimuli) when the distractor was an auditory stimulus. Despite some weaknesses, the current results provide insight into how selective attention and cognitive control may contribute to the development and maintenance of distinct psychopathic traits.