The pupils of psychopaths do not respond normally to distressing images or scenes, research reveals.
The pupils — the dark part of the eye in the centre — usually get bigger when people look at nasty images or something revolting.
Psychopaths, who display fearless dominance, do not show this response.
The reason is that strongly psychopathic individuals have little or no fear response, explained Dr Dan Burley, the study’s author:
“Our findings provide physical evidence of an emotional deficit common to psychopathic offenders.
The pupil has long been known to be an indicator of a person’s arousal.
Card sharks have learnt to look carefully at the eyes of their opponents to gauge if they have a great hand, and many an astute salesperson knows to up their price if your eyes reveal your excitement at their product.
Likewise, the pupil usually dilates when an image shocks or scares us.
The fact that this normal physiological response to threat is reduced in psychopathic offenders provides us with an obvious physical marker for this condition.”
Psychopaths fearless dominance
The conclusions come from a study of offenders, some of whom were psychopaths.
The results showed that psychopaths reacted normally to cute images of puppies and couples, but not to distressing images.
This suggests psychopaths do respond to emotions — just not all of them.
Professor Nicola Gray, who was involved with the project, said:
“This is one of the first times we have objective, physiological, evidence of an emotional deficit underpinning the offending behaviour of psychopathic offenders that does not depend on invasive methods or expensive equipment.
We hope to be able to develop this methodology to assist with clinical assessment and intervention in offender populations.”
Professor Robert Snowden, who supervised the research, said:
“Many psychopathic offenders appear to be bold, confident, and can act in cold-blooded manner.
It’s much easier to act bold if you have no feelings of fear, and to be cold-blooded if there is no emotion to get in the way of the act.”
The study was published by Cardiff University (Burley et al., 2017).