About 1% of people are a psychopath, and there are more men with the traits than women in the general population. To be diagnosed as one, you have to score highly on the Hare Psychopathy Checklist. But essentially psychopathy means being impulsive and thrill-seeking, while feeling no empathy for other people.
There isn't a lot of research on the differences in how psychopathic men and women behave. But as psychopaths are more likely than the rest of the population to be incarcerated for crime, and about 93% of the prison population is male, it's not farfetched to suggest male psychopaths may act more violently.
According to one study from 2012, published in the International Journal of Women's Health, female psychopaths are more likely to flirt and use their sexuality to manipulate people. They're more likely to be verbally aggressive and mean, and less likely to violently attack people. Psychopathic men, on the other hand, are more physically aggressive and more likely to commit fraud - perhaps why there are many more in prisons.
Another study, published in the Journal of Personality Disorders in 2017, found that female psychopaths are more likely to be anxious, have emotional problems, and be promiscuous.
Adrian Raine, a professor of Criminology at the University of Pennsylvania and expert of psychopathy, said he hasn't seen a lot in terms of research about how male and female psychopaths behave. But he told INSIDER the causes for psychopathy in men and women tend to be pretty much the same.
He calls psychopathy a neurodevelopmental disorder, because it is characterised by behaviour but is partly down to the structure of someone's brain.
The amygdala is largely where people process emotions. In psychopaths, this area is up to 18% smaller. When regular people are given a moral dilemma to consider, such as the trolley problem, the amygdala fires up and lights up on brain scans. In psychopaths, this doesn't happen to the same degree.
"We know that there's strong genetic contributions to the brain areas, but we also know that the social environment can impact the brain," said Raine. "People who are abused early in life or who are neglected for example, they have a reduction in the volume of the amygdala. That's at least true in children. So it can be genes and it can be the environment. Most likely, it's a contribution of both."
Raine didn't want to make any claims about male and female psychopaths, but he did say female psychopaths are definitely antisocial, like their male counterparts.
"I think if I had to speculate, if there is a general male female divide, that males are more aggressive physically than females," he said. "And if you look at women in prisons, a lot of it is drugs and a lot of it is prostitution. And I'm suspecting that in respect to female psychopaths, you'll see a similar reflection there."
Female psychopaths probably dabble in all sorts of criminal offences too, he added, but they're usually not the ones raping people.
"And they're much less likely to be committing homicide," he said. "When it comes to the sex differences in ratio it's really large - nine males for every female murderer. So I would think you'd get that with male and female psychopathy too."
Women, of course, do kill sometimes. In an article for The Conversation, Marissa Harrison wrote about her research looking at 64 female serial killers.
The results of the study found that most female serial killers were middle and upper class. Almost all of them were white, and had a degree or college education. Most of them also knew their victims - two thirds were related to them, a third murdered their significant other, and 44% killed their own children.
Primarily, Harrison's team found that female serial killers would murder people over money, rather than sex or rage, which are more likely to be motives for male murderers.
There is a strong sex difference with psychopaths in general, said Raine, but more research is probably needed to know the specific details.
It's a myth that all psychopaths are obsessed with death and homicide anyway. Due to their blunted emotions, psychopaths are more likely to be thrill-seekers, but they're not all that much more likely to commit murder than the rest of the population, Raine said.
"Most psychopaths don't kill," he said. "Most psychopaths are not violent. However, they are perhaps more likely to be violent, and more likely to commit homicide than other offenders."
It sounds contradictory, but that's because the rate of homicide is so low. If 1% of the normal population considers murder, then a psychopath may be two or three times more likely to, at 2-3% of them. That number is still relatively small.
"I wouldn't think psychopaths generally speaking have an unusual fascination with death more than the average person," Raine said.
"Male psychopaths, if they are going to kill, they are far more likely to than a female psychopath. But you'll always find examples of female psychopaths who kill. There's always exceptions."
Also from Business Insider South Africa: