The brain of a psychopath may be wired in such a way that it overvalues immediate rewards while downplaying the future consequences of dangerous or immoral actions, according to new Harvard research published in the journal Neuron.
The study, which relied on the brain scans of nearly 50 prison inmates, sheds light on why psychopaths make such poor decisions that often result in violence or other anti-social behaviors.
“For years, we have been focused on the idea that psychopaths are people who cannot generate emotion and that’s why they do all these terrible things,” said senior author Josh Buckholtz, associate professor of psychology at Harvard University.
“But what we care about with psychopaths is not the feelings they have or don’t have, it’s the choices they make. Psychopaths commit an astonishing amount of crime, and this crime is both devastating to victims and astronomically costly to society as a whole.”
“And 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. 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 they make decisions that involve trade-offs between the costs and benefits of action,” he said.
The researchers scanned the brains of 49 inmates over two hours as they participated in a type of delayed gratification test which asked them to choose between two options — receive a smaller amount of money immediately, or a larger amount at a later time.
The findings were then fit to a model that allowed researchers to rate how impulsive each participant’s behavior was and to identify brain regions that play a role in such choices. Participants who scored high for psychopathy showed greater activity in the ventral striatum — a brain region involved in evaluating the subjective reward — for the more immediate choice.
“So the more psychopathic a person is, the greater the magnitude of that striatal response,” Buckholtz said. “That suggests that the way they are calculating the value rewards is dysregulated — they may over-represent the value of immediate reward.”
When the researchers began mapping which brain regions are connected to the ventral striatum, things became even clearer.
“We mapped the connections between the ventral striatum and other regions known to be involved in decision-making, specifically regions of the prefrontal cortex known to regulate striatal response,” said Buckholtz. “When we did that, we found that connections between the striatum and the ventral medial prefrontal cortex were much weaker in people with psychopathy.”
This lack of connection is important, Buckholtz adds, because this portion of the prefrontal cortex role is thought to be important for ‘mental time-travel’ — envisioning the future consequences of actions.
There is growing scientific evidence that the prefrontal cortex uses the outcome of this process to change how strongly the striatum responds to rewards. With that prefrontal modulating influence weakened, the value of the more immediate choice may become dramatically over-represented.
“The striatum assigns values to different actions without much temporal context,” he said. “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.”
The effect was so pronounced, that the researchers were able to use the degree of connection between the striatum and the prefrontal cortex to accurately predict how many times inmates had been convicted of crimes.
“They’re not aliens, they’re people who make bad decisions,” said Buckholtz. “The same kind of short-sighted, impulsive decision-making that we see in psychopathic individuals has also been noted in compulsive over-eaters and substance abusers.”
“If we can put this back into the domain of rigorous scientific analysis, we can see psychopaths aren’t inhuman, they’re exactly what you would expect from humans who have this particular kind of brain wiring dysfunction.”
Source: Harvard University