A desire to punish wrongdoers may be highly influenced by emotional responses, according to a new study. Detailed knowledge of a crime leads those people in judgment to seek retribution, researchers found in a new experiment that could influence courts.
Vanderbilt University researchers in Nashville, Tennessee, examined brain scans showed that carefully planned crimes lead those in judgment to seek more severe punishments than they would otherwise.
Using functional magnetic resonance imaging (fMRI), investigators found the amygdala, part of the brain that controls emotion, was stimulated by graphic descriptions of crimes. When those acts were deemed to be premeditated, the brain wanted to seek justice and retribution. However, when the act was seen as accidental or unintentional, this natural response was tempered by electrical signals in the brain.
"A fundamental aspect of the human experience is the desire to punish harmful acts, even when the victim is a perfect stranger. Equally important, however, is our ability to put the brakes on this impulse when we realize the harm was done unintentionally," Rene Marois, psychology professor at Vanderbilt University, said.
Stories of one person bringing harm to another were read to 30 volunteers. The transgressions ranged from property damage to death, and two versions of each tale were used -- one factual and one designed to stir emotion. In half of the stories, the transgression was committed on purpose, while the harm was accidental in the other versions. At the end of each story, subjects were asked to determine a punishment for the person responsible for the harm.
This research could suggest that crime scene evidence, such as pictures, video and eyewitness testimony, could sway jurors to greater punishments, if the act was premeditated.
Brains of volunteers showed increased activity in both the amygdala, as well as the dorsolateral prefrontal cortex (dlPFC). This section of the brain plays an important role in decision-making when determining punishments. Versions of the stories where harm was unintentional also triggered a separate regulatory network in the brain, which suppressed the urge for revenge in the dlPFC.
"Although the underlying scientific basis of this effect wasn't known until now, the legal system recognized it a long time ago and made provisions to counteract it. Judges are permitted to exclude relevant evidence from a trial if they decide that its probative value is substantially outweighed by its prejudicial nature," Michael Treadway of Harvard Medical School told reporters.
Examination of the role of evidence and emotion in sentencing of criminals was published in the journal Nature Neuroscience.
