Contrary to the media depiction, a diagnosis of clinical psychopathy does not necessarily describe someone who enjoys sadistic violence, but instead describes an aggressive or antisocial person who also seems to have shallow emotions, manipulates others, and has a lack of guilt and empathy for victims.
These traits are usually measured by the use of a diagnostic checklist called the PCL-R.
One of the theories of psychopathy suggests that we learn to avoid treating others badly because their negative emotional reaction is also unpleasant for us.
Psychopaths, so the theory goes, lack the ability to perceive distress in others, and so have less reason to avoid treating others badly if it serves their needs.
A group of researchers, led by Dr Quinton Deeley, tested this theory by brain-scanning 15 psychopaths and 9 healthy controls while they viewed happy, sad and neutral faces.
The participants were asked to indicate whether the faces were male or female as a way of focusing participants on the faces and testing whether they could identify faces adequately, but the real comparison was for their reaction to different emotional expressions.
The researchers found that people with psychopathy show reduced activation in brain areas linked to vision and face perception in response to fearful faces, and surprisingly, also to happy faces.
They also showed less activation to fearful faces compared to neutral faces, which was the reverse of the pattern found in control participants.
These results suggest that psychopathy may involve a problem with identifying others’ emotional reaction that is particularly apparent for fearful faces.
However, a previous study with psychopaths reported that they do not show the same fearful response to mild pain when compared to controls, suggesting that the effect may not be specific to faces but a more general problem with fear-based learning.
Whether the problem with identifying fear in other people’s faces is a part of this, or an additional problem, remains to be seen.
It is known that both genetics and early life experiences, such as coming from a broken home, experiencing physical punishment and anti-social parenting, can contribute to psychopathy.
What remains to be answered is how much of the differences in brain function are due to inherited traits, and how much are the result of the brain developing in response to early experiences.
UPDATE: Dr Quinton Deeley discusses emotion recognition and psychopaths in the December Royal College of Psychiatrists podcast. The interview starts 27 mins 35 secs in.