In court arguments, the less gruesome the description of a crime, the less likely the punishment will match U.S. Federal Sentencing Guidelines, according to researchers at Duke University.
The team had study participants read vignettes of a perpetrator committing a crime while having their brains scanned by an MRI. The only times the study participants said the crime deserved punishment matching the guidelines was when the description of the crimes elicited strong disgust. Crimes considered less disgusting were judged worthy of significantly less punishment than the recommended guidelines.
The researchers wanted to examine how brain regions used in logical reasoning responded to the gruesome nature of crimes and biological descriptions of people's personalities. The disgusting nature of a crime and descriptions of the perpetrator's personality were found to influence logical reasoning among participants, according to the study.
"Legal decisions hinge on different inferences about the mind of the accused, like responsibility, culpability, intentionality," said senior author Lasana Harris, a professor of social psychology and cognitive neuroscience at Duke University. "If the focus is drawn away from the mind of a perpetrator by providing biological explanations of personality instead of traits, people may not make the same social cognitive inferences.
"Similarly, many years ago our legal systems were perhaps built with violent, gruesome crimes in mind," Harris said. "Therefore legal penalties for crimes better match people's modern intuitions when the crimes are gruesome. Both factors -- the mind of the accused and the gruesomeness of the crime -- demonstrate built-in bias within the legal system."
The study appears online in the U.K.-based journal Social Neuroscience (Taylor & Francis, pub. http://tinyurl.com/odhglan).
Seventeen participants read 84 vignettes for 20 seconds each on a computer screen that depicted the details of a perpetrator committing a crime. The vignettes described crimes that elicit strong or weak disgust. The study also matched responses with the punishment severity called for by the Federal Sentencing Guidelines and the North Carolina Sentencing Manual.
Finally, an extra sentence described the perpetrator's personality using biological language, such as the perpetrator had a "genetic predisposition to aggressive behaviors," or traits -- the perpetrator was an "aggressive person."
Neuroimaging results indicated that brain regions active during logical reasoning responded less to crimes weak in disgust and to biological descriptions of a perpetrator's personality. This, they said, demonstrated the impact of emotion and social cognition on logical reasoning mechanisms necessary for legal decision-making.
A sample vignette that generated strong disgust read:
"Rob Whitley was on his lunch break. He saw his boss at the hot dog stand and approached him while taking out a pair of scissors. He stabbed his boss on the side of the neck first, and then the lower back, causing the victim serious blood loss and requiring hospitalization."
A vignette weak in disgust read:
"John Noel was at a bar and saw his ex-girlfriend's new lover, James. Although John was not expecting to see James there, John took out the gun that he regularly carried from his back pocket and tried to shoot James, but missed."
Both of these crimes would be punishable for aggravated assault, and have an offense level of 19 on the Federal Sentencing Guidelines. Study participants chose punishment values in ranges, mimicking actual sentences for crimes.
While participants accurately matched federal standards for the strong disgust vignettes, they suggested less punishment than the standards recommend for crimes considered weak in disgust.
Parts of their brain engaged in logical reasoning also reflected this bias. Logical reasoning areas responded less when faced with biological descriptions of the perpetrators' personality and when faced with less gruesome crimes.
Harris added that attorneys can influence jurors' cognitive processes and final decisions by the level of gruesome details and biological explanations of personality they present during a trial.
"But, of course, we expect that good lawyers are inherently aware of this, given the increased use of scientific evidence like brain scans in the courtroom," he said.