Psychopathy is a poorly understood phenomenon. It used to be thought of as exclusively psychological, but it’s increasingly looking like it’s partly neurological in origin, in that the brains of psychopaths are wired differently. It’s not even very well defined – it involves a range of behaviors, not just one – and certainly doesn’t mean someone is necessarily “crazy.”
With all this confusion, it makes sense that researchers are now turning to chimpanzees, our most closely related fellow apes, to understand psychopathy better. Chimpanzees are free of human societal constraints, and as such, they represent a model study for the innate nature – or lack thereof – of psychopathy.
As reported by the British Psychological Society, recent work on our evolutionary cousins suggests that there’s a clear genetic basis for psychopathy.
A Georgia State University-led team carefully observed 164 of these primates housed at two research centers, one in Atlanta and another run by the University of Texas. Two or three handlers were assigned to each chimpanzee, with the requirement being that they knew them well.
Assessing psychopathy in humans is normally done via a psychological evaluation, and sometimes using magnetic resonance imaging (MRI) scans on the brain. The way people describe their normal behaviors and proclivities, and the flow of blood in the brain to and from the amygdala – the “fear center” – are often good ways to see if people have psychopathic tendencies.
This is not so easily achieved in chimpanzees, who aren’t known for being particularly conversational or happy to sit in extremely noisy MRI scanners. Amazingly, there exists something called the CHMP-Tri scale, a sort of personality test specifically designed for chimpanzees.
This scale looks for callous aggression, and lack of restraint, and propensity towards bold behaviors. All these are suggestive of psychopathy, and these can be observed without needing to ask the chimpanzees any direct questions.
The researchers also looked for a specific gene known as AVPR1A. This is known to influence the production of vasopressin, a hormone found in most mammals that primarily deals with water retention and blood vessel sizes. There’s mounting evidence that suggests it also drives sexual motivation, stress and social behaviors, including those linked to psychopathy.
Going yet another step further, the chimpanzees’ individual life experiences were also taken into account. Whether they were reared by their own mother, or abandoned; whether they had been severely injured early on in life, or reared by people, and so on.
So what did they discover? Well, as ever, there’s no simple answer to what drives or causes psychopathy – but genes play a major role.
For chimpanzees that were raised by their own mothers, variations in the AVPR1A gene were not linked to callous aggression, but were associated with boldness and a lack of inhibitions, as well as their overall psychopathy “score.” For those that were reared by people, there were no correlations between the gene and their overall psychopathic tendencies.
At a glance, then, this suggests the appearance of this gene influences psychopathy, unless you’re raised by an entirely different species from a young age. There’s no human analog to this, of course – so this correlation is tricky to interpret.
However, all this does imply that AVPR1A – and by association, levels of vasopressin – does seem to influence psychopathy.
The Frontiers in Neuroscience study notes that “in both humans and chimpanzees, recent research suggests a strong genetic contribution to individual variation in psychopathic traits.”
Essentially, instead of being something purely psychological in nature, psychopathy is looking more and more like it has a physical basis, in both neurology and genetics. That paves the way for not just better diagnoses, but better treatment as well.