Study discovers the ordinary psycho

Jeremy Renner as Sergeant First Class William James in The Hurt Locker was 'a bit of a cowboy'. Photo / Supplied

There's more to psychopaths than being murderous. They aren't all as smart as Hannibal Lecter, or evil, and they can change, say researchers.

Victoria University Associate Professor Devon Polaschek, one of four authors of research about to be published in Psychological Science in the Public Interest, says psychopaths of the popular imagination give the personality disorder a bad name.

Patrick Bateman in the film American Psycho inserts a chainsaw into a prostitute. Alex in A Clockwork Orange fantasises about torture and slaughter while listening to music.

But psychopaths can wreak havoc in workplaces without stabbing, or eating, their colleagues.

"It's a much more ordinary condition than those movies portray. They aren't more intelligent than the rest of us," Dr Polaschek said.

She suggested another movie character for a different look at psychopaths: Sergeant First Class William James in The Hurt Locker.

James joins a bomb disposal team in Iraq and quickly earns the distrust of his comrades through his lack of care.

"He could well be a psychopath, but he doesn't do anything to hurt anybody. He's a bit of a cowboy and does a fearless kind of work tracking those improvised explosives, and he doesn't work well in a team."

Dr Polaschek's research found that psychopathy was poorly understood. A broader definition of the personality disorder has been suggested, in which people are considered psychopaths if they are a bit too much of at least two of the following: bold, impulsive, mean.

"People with boldness and impulsiveness might be a problem for their co-workers and managers, but they aren't necessarily going to be involved in any crime. They will tend to mess things up because they don't think things through. Maybe they drink too much, but they're not out to hurt people," she said.

"It's not Hannibal Lecter or any favourite super-criminal at all. It's a personality that isn't socially attractive, but not malevolent, evil or criminal either."

Dr Polaschek said there were signs that psychopathic behaviour could be modified.

Adolescent psychopaths, in particular, could end up being tolerable - if not saintly - adults.

She said there should be more ways to measure and identify psychopaths.

Psychopaths have been thought to be at least as common as one in 100 people, though the estimate is unreliable because of the focus of the previous research.

Dr Polaschek said it was a complex disorder - there was no clear line dividing a common and commendable display of boldness from full-blown psychopathy.

"But there probably isn't such a thing as a harmless psychopath. People who live for themselves and for the day will tend to blunder around, causing harm to people - because that's not how society works."