Psychopathy May Be An Adaptation, Not A Disorder

As I have written before, members of our Research team, with our colleagues at the Clarke Institute and Queen's University, have studied psychopathy for many years. A while back, I mentioned our theory that psychopathy is not a disorder. A disorder, by definition, is the failure of some physical or mental feature to do its natural, evolved function.

We think evolution designed a subgroup of humans to use aggression and deception to get resources from others. In theory, such people ought to have: skill at deception, lack of concern for the suffering of others, willingness to use violence, ease and flexibility in the exploitation of others, lack of concern for the opinion of others, and extreme reluctance to be responsible for others (including, for males, their own offspring).

Males of this subgroup would also engage in lots of uncommitted sex. These are all psychopathic traits. The point is that psychopathy is not a disorder because psychopaths (and their psychological characteristics) are doing exactly as they were designed by natural selection. According to this view, psychopathy is an adaptation.

Research on psychopaths shows big differences in the ways they act (impulsive especially in the presence of rewards), process information (unaffected by emotionally powerful information), and learn from experience (resistant to punishment). These have been thought of as defects, but it is just as possible they are adaptations that underlie a life long aggressive, cheating, and manipulating strategy.

A strategy that, if the psychopath keeps moving around to find new victims, and if there are not too many psychopaths, leads (more importantly, in past generations, led to) reproductive success. This theory does not necessarily say that psychopaths are especially economically or socially successful. The theory says that it is reproductive success (having offspring that grow up to have their own offspring) that matters most.

Also, the theory puts the basis for psychopathy in the past -- called ancestral environments; what matters is whether psychopathic traits led to success then. Finally, the theory does not say that this psychopathic strategy is more successful than a cooperative, prosocial one. It just says that, if most people are caring, cooperative, and trusting, that creates an opportunity to get along by cheating, bullying, and exploiting them.

At first glance, it might seem impossible to test a theory that says that everything happened many generations ago. But we have managed to think of some ways using data collected in the present. First, other researchers have discovered that violent people have high rates of particular types of medical problems in their histories -- obstetrical problems (toxaemia, Rh factor, maternal substance abuse, etc.), and perinatal difficulties (e.g., prematurity, low birth weight, severe fetal distress). Such problems are also associated with schizophrenia. These findings suggest that violence can be the result of problems in very early physical development, and that schizophrenia is a true disorder of neurological development. (It is interesting that people with schizophrenia are not especially violent, however.)

What does our adaptation theory say should be found in the prevalence of these medical problems among psychopaths? Because the theory says that psychopathy is not a disorder of neurological development, psychopaths should have fewer of these problems than other violent offenders. And that is what we found. If psychopathy were an extreme disorder (and knowing that these problems are associated with violence), one would predict that psychopaths would have high rates of these problems, but we found the opposite.

We also tested our theory with another measure of developmental stability -- fluctuating bilateral asymmetry. That is a polysyllabic way of saying, the degree to which the left side of the body is exactly the same size as the right side. In all species, the two sides of the body are genetically programmed to be the same size -- symmetrical. The amount of difference between the two sides, asymmetry, is a measure of the instability in a person's development. Again, violent individuals have been reported to be asymmetrical as have persons with schizophrenia. What about psychopaths? Our research showed that violent offenders who were also psychopaths were more symmetrical than those who were not psychopaths.

Again, although psychopaths are the most dangerous offenders, they do not have signs that their neurological development has been disrupted. From a medical point of view, they appear to have had healthy development compared to persons with schizophrenia or mental retardation.

Of course, our theory definitely says that the nervous systems of psychopaths must be different somehow. But that difference should not, according to the theory, look like damage. In fact, attempts by other researchers to find signs of damage in psychopaths using neuropsychological tests or fancy imaging methods (CT, PET, MRI scans, etc.) have not panned out.

So far at least, it does not look as though psychopaths have damaged brains, even though it does appear that their brains are different.

This theory says that psychopathy is inherited; does that mean nothing can be done to change violent psychopaths? People often think that genetic and environmental influences are in contrast; they often think that if something is inherited then it is not affected by the environment.

In fact, this is a big misconception. Almost every inherited human trait or behaviour is very strongly affected by the environment. As a simple example, we all inherit the `ability' to form callouses on our hands, but when, where, and how callouses form on your hands is determined by your environment. That is, the expression of an inherited trait is almost completely determined by the environment. What can we do to affect the expression of psychopathy?