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The scientists went to prison to work with convicted psychopaths. Reuters

The way psychopaths' brains are wired may explain why they make poor decisions that often result in violence, scientists have said. The connections in their brain may lead them to over-value immediate reward without thinking of the consequences of their dangerous actions.

Most studies on psychopathy portray psychopaths as devoid of feelings. This lack of emotions is thought to be the main reason many commit horrifying crimes.

But in a paper now published in the journal Neuron, researchers have shown that this theory may not reflect the entire story. Looking at why psychopaths take the decisions they do rather at their emotional state may be much more informative.

"Even though psychopaths are often portrayed as cold-blooded, almost alien predators, we have been showing that their emotional deficits may not actually be the primary driver of these bad choices," lead author Josh Buckholtz, from Harvard University, said in a statement.

"Because it's the choices of psychopaths that cause so much trouble, we've been trying to understand what goes on in their brains when the make decisions that involve trade-offs between the costs and benefits of action."

Going to prison

To conduct the study, Buckholtz and colleagues had to go to two medium-security prisons, to work with 49 male inmates who had been sentenced after committing violent crimes. The process involved using a mobile scanner to image the brain of as many volunteers as possible, as quickly as possible.

The participants were tested to see the extent to which they displayed characteristics of psychopathy. Their brains were also scanned as they took part in a type of delayed gratification test. It involved making a choice between receiving a small amount of money immediately, or a larger one, but at a later time.

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One of the most famous scenes in the movie American psycho. Flickr/Creative commons/Steve

The data allowed the researchers to create a model to measure not only how impulsive each participant's behaviour was, but to identify brain regions that play a role in assessing the relative value of such choices.

They found that inmates who had scored high for psychopathy showed greater activity in a region of the brain called the ventral striatum - known to be involved in evaluating the subjective reward - when presented with the more immediate choice. This suggest they value the immediate choice more than other, less psychopathic individuals.

"So the more psychopathic a person is, the greater the magnitude of that striatal response," Buckholtz pointed out. "That suggests that the way they are calculating the value rewards is dysregulated - they may over-represent the value of immediate reward."

The scientists then mapped the connections in the brain of the participants and discovered that the connections between the striatum and the ventral medial prefrontal cortex, an area involved in decision-making, were much weaker in people with psychopathy. This was even more noticeable in people who had been convicted of multiple crimes.

These connections between the striatum and the prefrontal cortex are thought to be crucial for people to envision the future consequences of their actions. Weak connections could explain why psychopaths make impulsive, sometimes even dangerous decisions without thinking of the long-term implications.

"We need the prefrontal cortex to make prospective judgements how an action will affect us in the future - if I do this, then this bad thing will happen. The way we think of it is if you break that connection in anyone, they're going to start making bad choices because they won't have the information that would otherwise guide their decision-making to more adaptive ends," Buckholtz explained.

The goal of this research is go beyond the popular image of psychopaths as incomprehensible, cold-blooded monsters. Showing that these are everyday humans whose brains are simply wired differently is a first step in achieving this.

The findings could also provide clues for how best to 'treat' psychopaths.

"The best treatment work on psychopathy to date suggests that intervening early - in adolescence - likely has the most benefit for reducing problematic behaviours. Our work suggests that interventions focused on helping these individuals better represent and focus on the future costs and consequences of their behaviour may be helpful. It's too early to suggest a specific treatment that would follow from our research, though," Buckholtz concluded.