Hear the word 'psychopath' and you're probably picturing someone like Hannibal Lecter, the evil psychopath and cannibal from 'The Silence of the Lambs' movie.

But if you've watched the movie, you'll know Jodie Foster's character Clarice Starling comes face to face with Dr. Hannibal when he's behind bars, his evil side already exposed. 

But would she know how to spot a psychopath if there was one next to her?  And would you?  Researchers in Hong Kong think they've uncovered a key characteristic that gives them away - but it's creepy.

The one thing many of them share in common is that they are very good liars.  

Rather than researching criminal psychopaths, the study recruited 52 students and used a simple experiment involving photographs of people.

The photos included people who were known and unknown to the students.  They were asked if they recognize the people in the photograph and were then prompted to pretend whether they knew them or not, according to the Daily Mail.  

The researchers then measured the time it took for the students to answer and also measured their brain activity as they formulated their answer.  After a break, the process was repeated again.

Those with higher levels of psychopathic traits were those who were fastest at giving answers that were lies.  Those who needed more time to give their answer had lower levels of psychopathic traits, the researchers said.

In the end, the researchers found that students who had low psychopathic traits took the same length of time to give the true answer as the false.

Out of the group, 23 students demonstrated low levels of psychopathic traits while 29 had high levels. 

Researcher Dr Robin Shao explained that 'high psychopathy is characterised by untruthfulness and manipulativeness.'  But the specific question the study wanted to resolve was whether psychopaths 'lie more or better than others.'

Now she and the team think they know the answer to this question.  She said: 'Our findings provide evidence that people with high psychopathic traits might just be better at learning how to lie.'

Lead researcher Dr Tatia Lee explained the significance of the findings.  'Lying requires a series of processes in the brain including attention, working memory, inhibitory control and conflict resolution which we found to be reduced in individuals with high levels of psychopathic traits,' she said. 

'By contrast, in individuals with low levels of psychopathic traits this lie-related brain activity increased.  'The additional 'effort' it took their brains to process untruthful responses may be one of the reasons why they didn't improve their lying speed.'