One key subtle sign could signify someone is a psychopath just by looking at them

Wouldn't it be handy if there was a subtle way you could find out if the stranger sitting next to you on the bus is a psychopath?

Well, it turns out that there's a well researched method to do just that and it probably wouldn't take too long.

Firstly, it's important to define a 'psychopath', which according to the NHS, is someone who is considered to have a severe form of antisocial personality disorder.

The disorder is often characterised by impulsive, irresponsible and criminal behaviour.

But to be clear, psychopaths are considered to have a severe form of antisocial personality disorder. So don't worry if you're a little awkward around new people, it doesn't mean you're a serial killer.

Anyway, a 2018 study by researchers at the Cardiff and Swansea Universities has seemingly determined a test for a psychopath.

It did this by taking a look at the effects of graphic and nasty images would have on people who are psychopaths and offenders.

Lead author Dr Dan Burley, from Cardiff University’s School of Psychology, said: "Our findings provide physical evidence of an emotional deficit common to psychopathic offenders."

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When looking at the graphic images - which would include a range of audio and visual aids - researchers noticed a subtle difference in eye responses.

The eyes of psychopathic offenders did not show pupil enlargement, while those of non-psychopathic offenders did.

Burley explained: "The pupil has long been known to be an indicator of a person’s arousal.

"Card players 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."

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Professor Nicola Gray, a clinical and forensic psychologist from Swansea University who provided clinical supervision for the project, added: "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 from Cardiff University, who supervised the research, concluded: "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."