Four Neuropsychological Models
Recent work in neuroscience is revealing that the brains of psychopaths are different from those of normal people in several interesting ways. Whether these differences should be considered malfunctions of brain systems that operate in normal people, or are part of a genetically different type of brain, will probably have to be decided on a case-by-case basis. But whatever the cause of these differences, they raise the question as to whether psychopaths can be held legally responsible for the mayhem they create. We exempt people with schizophrenia and very low IQs from legal responsibility—so why should we not do the same with psychopaths?
Currently there are four different theories, or models, offering explanations or reasons why these differences in the brains of psychopaths cause them to be so callous towards others, and such a danger to society at large. I will describe these four approaches in the sections below; then, at the end of the article, I consider briefly how some of the findings that have been used to support the different theories may also be used to construct a hypothesis according to which at least some psychopaths are clearly legally responsible.
The attentional model
According to Joseph Newman and his colleagues, the primary problem in psychopathy is a failure of what he calls “response modulation” (Hiatt & New- man, 2006; Motzkin, Newman, Kiehl, & Koenigs, 2011; Newman, Patterson, & Kosson, 1987). Normal people are able to alter what they are doing when the demands of the task change. Thus, when we undertake a task, we focus our attention on certain parts of that task—but sometimes information in the periphery becomes relevant and the new infor- mation should force us to change our actions. The brain contains two attentional systems: top-down and bottom-up. Top-down attention tends to be un- der voluntary control; bottom-up attention is invol- untary, and can temporarily capture top-down at- tention—as when movement in the periphery of our visual field attracts our attention. Psychopaths have trouble using top-down attention to accommodate information that activates bottom-up attention during a task whereas in normal people, this pro- cess tends to happen automatically: thus, when the hunter is scanning for deer, a rabbit hopping into the periphery of his visual field automatically attracts his attention and disrupts his action plan.
Once they have started on a task, psychopaths are remarkably insensitive to changes in the pat- tern of rewards. In one revealing study, psychopaths were shown a series of playing cards on a screen. They were told that they would receive one point for each face card but lose a point for each non-face card; however, the deck was deliberately stacked so that the first ten cards were face cards, then nine of the next ten, then eight of the next ten, and so on. Subjects were told they could stop playing at any time. Non-psychopaths noticed the worsening trend and stopped playing after seeing around 50 cards; psychopaths played blindly on, though, until their early winnings were gone.
The amygdala model
James Blair and his colleagues have argued that the amygdala and ventromedial prefrontal cortex (vmPFC) are the core dysfunctional areas in psy- chopathy (Blair, Mitchell & Blair, 2005; Marsh & Blair, 2008). The amygdala has many functions but some of the primary ones involve the production and regu- lation of emotions. The notorious lack of fear shown by psychopaths thus points to an amygdala dysfunc- tion. In line with this paradigm, Adina Roskies has suggested that vmPFC patients have normal rea- soning capacities, but are simply not motivated to act on moral beliefs (Roskies, 2003, 2006). This may be due to their inability to experience moral emo- tions such as empathy. For example, when patients with ventromedial damage are asked to provide an answer to the famous “trolley” thought experiment, where subjects must decide whether to intention- ally kill one person to save five, they are more likely than normals to judge that killing the one person (by pushing him onto the trolley tracks) is the right thing to do, despite their having an active role in the kill- ing, in that scenario. They don’t experience the same reluctance of normals, whose empathic emotions attempt to inhibit the fatal push.
When the brains of normal subjects are imaged while they are being presented with moral dilem- mas having a strong emotional character, activity is observed in a network including the amygdala, medial prefrontal cortex, posterior cingulate gyrus, and the angular gyrus. This network has been found to be active during “self-referential thinking, emo- tional perspective taking, recalling emotional expe- riences to guide behavior and integrating emotion in social cognition” (Glenn, Raine, & Schug, 2009, p. 6). On the other hand, Glenn and her colleagues found reduced activity in the amygdalae of psycho- paths during emotional decision-making; they also found that a subgroup of these subjects, who were particularly skilled at conning and manipulation, showed reduced activity within this “moral” circuit. “Dysfunction in these regions,” they say, with the ap- propriate guardedness, “suggests failure to consider how one’s actions affect others, failure to consider the emotional perspective of the harmed other, or a failure to integrate emotion into decision-making processes” (2009, 6).
The paralimbic model
Kent Kiehl accepts that the amygdala is dysfunc- tional in psychopaths, but implicates a much wider problem area, called the paralimbic cortex. This col- lection of cortical areas includes the anterior cingu- late, posterior cingulate, superior temporal, insular and hippocampal cortex. The insula, hidden in the fold that separates the temporal lobe from the lat- eral cortex above it, has been found to activate when a subject detects violations of social norms. It also activates when subjects experience anger, fear, em- pathy, and disgust (Kiehl & Buckholtz, 2010). Given that the insula also plays a role in pain perception, dysfunction there may explain experimental findings in which psychopaths were insensitive to the threat of impending pain—in this case an electric shock that was never actually delivered.
Cognition without the proper mix of emotion (or, more neutrally, autonomic activity)— whether it is too much or too little emotion—may be aimless, and subject to being sidetracked by poor reasoning. The role of emotion in cognition goes beyond that of merely inhibiting us from doing harmful, illegal, or counterproductive things; it guides our reason- ing, and can provide us with a sense of how strong or weak an argument is. For example, Baird and Fugelsang (2004) found that adolescents take longer to make moral decisions partly because they have yet to develop the “gut feeling” that requires peo- ple to stop considering a decision when an immoral or harmful result is realized. Without this feeling, a strong reason to do x and a weak reason to not do x can appear to be equal, and this can have a sort of neutralizing effect—in which a weak argument and an opposing strong argument seem to be equal inforce. So, in the mind of the psychopath, the way is clear to proceed with the (harmful) action.
The executive model
Executive processes exist mainly in the brain’s frontal portions. They are responsible for planning and inhibiting actions, as well as allowing emotions to influence cognition in the proper way, so there is reason to think psychopaths may have a problem in this realm. Morgan and Lilienfeld (2000) conducted a meta-analysis of the existing research on execu- tive functioning in people diagnosed as exhibiting antisocial behavior—a large category that includes those diagnosed with antisocial personality disor- der, as well as those diagnosed as psychopathic— and found that the antisocial behavior group scored .62 standard deviations worse on tests of executive functioning, which yielded a medium to large effect size.
Since then, several attempts have been made to delineate subtypes within the category of psy- chopaths in order to discern whether some groups might have more severe executive function deficits. Gao and Raine (2010) distinguished two categories of psychopath, which apparently have very differ- ent executive profiles: successful psychopaths with a minimal or no criminal record, and unsuccess- ful psychopaths, currently incarcerated or with a substantial criminal record. They found that un- successful psychopaths show reduced prefrontal and amygdala volumes in addition to hippocam- pal abnormalities, resulting in reduced executive functioning, including impaired decision-making. Unsuccessful psychopaths also show abnormal fear- conditioning, which is thought to contribute to poor and risky decision-making (Birbaumer et al., 2005).
Successful psychopaths do not show similar structural and functional impairments of the pre- frontal cortex, amygdala and hippocampus. In fact, in a study designed specifically to produce em- barrassment, where subjects had to prepare and then deliver a two-minute speech detailing their personal faults and weaknesses, Ishikawa and col- leagues found that successful psychopaths actually had greater autonomic responses than both unsuc- cessful psychopaths and normal controls (Ishikawa, Raine, Lencz, Bihrle, & Lacasse, 2001). This study also found that, compared with unsuccessful psy- chopaths (i.e., those who had at least one criminal conviction), successful psychopaths had enhanced executive functioning as measured by the Wiscon- sin Card Sorting Task (WCST). The WCST is used to assess the frontal lobe functions used in strategic planning, organised searching, shifting of cognitive sets, considered attention, and modulating respons- es. Indeed, the successful psychopaths performed significantly better on the WCST than non-psycho- pathic controls while, in contrast, the unsuccessful psychopaths scored lower than the controls. The authors of this study suggested that better execu- tive functioning might play a protective role for suc- cessful psychopaths, thus decreasing their tendency to be caught up in the criminal justice system. This executive profile may also make successful psycho- paths more effective at manipulating people.
In a series of recent articles, my colleague Katrina Sifferd and I have argued that the executive prob- lems of psychopaths are relevant to their legal and ethical status in our society (Hirstein & Sifferd, 2011; Sifferd & Hirstein, 2013). Given the roles of execu- tive processes in planning actions, and directing at- tention while the action is underway, and possibly stopping or altering the action based on its effects on others, they are extremely relevant to moral and legal responsibility. Our hypothesis, in short, is that executive processes are in fact the seat of legal re- sponsibility, and that people with intact executive processes are responsible for their intentional ac- tions. This implies that successful psychopaths in general should be held legally and morally responsi- ble for their destructive actions. On the other hand, since unsuccessful psychopaths may lack the abil- ity to alter or inhibit actions, they are less legally responsible for what they do, according to our ap- proach. On the bright side, executive processes are trainable, and there is some initial evidence of success in training psychopathic inmates to employ them more effectively.