The biology of psychopathy and empathy
Topic: Science & Technology
Researchers have found that psychopathy may be an inherited trait.

An article in The Economist "Original sinners?" reported the results of a study on twins' behaviour. Many of the twins studied had a tendency to bad behaviour and for the display of callous and unemotional traits, such as a lack of feelings of guilt after doing something wrong, or not having at least one good friend. In adults, callous and unemotional traits are symptoms of psychopathy.

The findings were reported as follows:

Based on the teachers' assessments, the researchers identified the naughtiest 10% of the individuals in their sample—in other words those with severe conduct disorder. They then subdivided these children into those with psychopathic traits and those without and asked, in each case, whether an individual's twin showed bad behaviour, psychopathy, or both.

Their analysis showed that bad behaviour without psychopathy has relatively little genetic component—less than a third. By contrast, four-fifths of the difference in behaviour between the general population and children with psychopathic traits seems to lie in the genes.

The article concluded that if there is a genetic basis for psychopathy, there is probably a selective advantage to the trait.

If it does, such an advantage probably pertains only when psychopaths are in the minority (a state of affairs known to biologists as a balanced polymorphism). But it does mean that far from being an aberrant behaviour, psychopathy may be disturbingly normal.

Callous and emotional traits are related to empathy, or more accurately, the lack of it. An earlier article in The Economist "A mirror to the world" discussed the biological basis of empathy.

Essentially, empathy appears to rely on a type of nerve cell known as a mirror neuron. A mirror neuron is one that is active when the individual whose brain it is in is engaged in some action or experiencing some sensation or emotion, and also when that particular action, sensation or emotion is being observed in someone else. A lack of mirror-neuron activity is considered to be at least part of the cause of autism.

The idea that traits such as empathy and psychopathy have biological and even genetic bases will inevitably be controversial to society, as most claims of genetic linkages in personality traits tend to be. However, it is the job of scientists to discover the science behind the traits, and the responsibility of society as a whole to determine what to do with the discoveries.