New research from The Australian National University (ANU) has found people with high levels of psychopathic traits have difficulty telling when someone is genuinely afraid or upset, based on people's facial expressions.

The study involved participants looking at photographs of faces expressing different emotions. Some faces were showing real emotions and others were faking it.

Lead researcher Dr Amy Dawel of the ANU Research School of Psychology said the results showed people with high levels of psychopathic traits don't respond to genuine emotions in the same way as most people.

"For most people, if we see someone who is genuinely upset, you feel bad for them and it motivates you to help them," Dr Dawel said. "People who are very high on the psychopathy spectrum don't show this response."

"We found people with high levels of psychopathic traits don't feel any worse for someone who is genuinely upset than someone who is faking it. They also seem to have problems telling if the upset is real or fake. As a result, they are not nearly as willing to help someone who is expressing genuine distress as most people are."

Interestingly, these problems in responding to other peoples' emotions seem to be just for people who are sad or afraid.

"For other emotions such as anger, disgust, and happy, high psychopathy individuals had no problems telling if someone was faking it. The results were very specific to expressions of distress."

Dr Dawel hopes her research will lead to better understanding and treatments for psychopathy.

"There seems to be a genetic contribution to these traits, we see the start of them quite early in childhood," she said.

"Understanding exactly what is going wrong with emotions in psychopathy will help us to identify these problems early and hopefully intervene in ways that promote moral development."

The study, titled 'All tears are crocodile tears: Impaired perception of emotion authenticity in psychopathic traits. Personality Disorders: Theory, Research, and Treatment' has been published in the Personality Disorders journal.