Among social animals, humans are unique in their willingness to punish the deserving, even at a personal cost. And thanks to a new study published today in Neuron, we have a better idea of where our sense of justice comes from—specifically, a brain area known as the dorsolateral prefrontal cortex (DLPFC).
“Despite the centrality of such third-party punishment decisions to modern institutions of justice, we don’t know very much about how the brain combines evidence of intentionality and harm,” said study co-author Joshua Buckholtz of Harvard University. “Our study provides new insight into how humans make these judgments.”
What we knew before is that the success of the human species often relies on our ability to cooperate together on a large scale, which requires us to establish and enforce social norms. The DLPFC is one of the most recently evolved areas of the brain, and it would make sense that it would have evolved to fit the new need to punish norm-breakers—so the team from Vanderbilt and Harvard decided to test it for this function.
Brain Law and Order
The researchers studied 66 men and women as they were asked to rate the blameworthiness or the amount of punishment deserved for various hypothetical situations. The situations ranged from assault to murder, with potentially mitigating factors like duress and psychosis thrown in.
While making these decisions, half of the group had the activity in their DLPFCs disrupted via repetitive transcranial magnetic stimulation (rTMS)—a noninvasive and targeted method to stimulate specific brain areas using magnetic fields. The other half had a sham or placebo rTMS done on them.
For the 33 who had their DLPFCs interrupted by the magnetic fields, the ratings of blameworthiness were entirely unaffected, but the level of punishment dropped. Closer analysis revealed that rTMS seemed to cause the subjects to base punishment decisions more on the consequences of the crime rather than on the criminal’s intentions—so punishment ratings were lowered only when a deliberate crime resulted in minimal damage.
In a separate experiment, the team imaged the brains of the subjects using an fMRI as they rated either blameworthiness or punishments. The DLPFC lit up more during punishment decisions, and showed sensitivity to culpability in terms of punishment (but not blameworthiness).
This suggests that the DLPFC weighs and balances information regarding intent and harm in order to reach an appropriate punishment—but receives this information from other brain regions.
“We were able to significantly change the chain of decision-making and reduce punishment for crimes without affecting blameworthiness,” said René Marois, professor and chair of psychology at Vanderbilt and co-principal author of the study. “This strengthens evidence that the dorsolateral prefrontal cortex integrates information from other parts of the brain to determine punishment and shows a clear neural dissociation between punishment decisions and moral responsibility judgements.”
Does this mean we’re going to have changes in courtrooms?
The study may have implications in regards to the legal system: “This research gives us deeper insights into how people make decisions relevant to law, and particularly how different parts of the brain contribute to decisions about crime and punishment. We hope that these insights will help to build a foundation for better understanding, and perhaps one day better combatting, decision-making biases in the legal system,” said co-author Owen Jones, professor of law and biological sciences at Vanderbilt and director of the MacArthur Foundation Research Network on Law and Neuroscience.
However, it probably won’t change much for the time being.
“While this study does provide new insight into how human brains make decisions of the kind that judges and jurors make daily, the effects that we report are modest in size, and it’s unclear how they would generalize to trial courts. The value of this study lies in its ability to reveal the basic mechanisms of norm-enforcement decisions,” said Marois. “Magnetic brain stimulation will not be coming to a courtroom near you anytime soon.”
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Feature Image: Thinkstock
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