Since colonial times, Americans have had a deep interest in crime and the not-always-inevitable punishment. Now, a new study has used brain imaging techniques to look at the neural circuitry influencing any decision about how severely someone should be punished after hurting another. Surprisingly, emotion does not rule the day. The neural circuits which help us decide whether an act was intentional or unintentional override any emotional urge to punish, the study finds, even when gruesome details of a crime are provided.

Crime Stories Have Always Been Popular

Among the very first books written by American colonists of the 17th Century were the captivity narratives. Essentially, these were simple memoirs written by people imprisoned by the Indian tribes, and featured harrowing tales of their moment of capture and their travels with the natives. Generally, each story ends when relatives find and purchase back the unwilling prisoner, who happily returns home. These stories were written in a manner that is best described as trauma-induced, with details recounted in a quick, if numb, style. Hugely popular in England, these stories of captivity offered a taste of the wild New World. While most end at the moment of homecoming, in rare cases, the authors would describe their dreams of punishing their captors.

What exactly goes on in our minds when we decide how to punish another? To understand this mental process, a team of researchers led by Dr. Rene Marois, a professor of psychology at Vanderbilt University, devised an experiment in which 30 volunteers had their brains scanned while they read a series of scenarios. The scenarios described how a character named John brought harm to either Steve or Mary in the form of death, maiming, physical assault, or property damage. In half of the scenarios, the harm was clearly identified as intentional, and in the other half it was clearly identified as unintentional. The volunteers read two versions for each scenario: one, a simple matter-of-fact description, the other, a lurid description. After reading each, participants rated the level of punishment John deserved on a scale from zero (no punishment) to nine (most severe punishment).

How did the volunteers mete out John's punishment? Severity was significantly influenced by John's intention yet also by the style of the description. When victim's suffering were described in a lurid fashion, participants punished more severely than when suffering was described matter-of-factly. However, in cases where the harm was unintentional, lurid descriptions had no effect.

Things get even more interesting when the researchers looked at the brain scans. The amygdala, known to play a role in processing emotion, responded strongly to the graphic language. However, this effect only occurred when John intentionally harmed his victim. Additionally, in these situations, the amygdala showed stronger communication with the dorsolateral prefrontal cortex, an area critical for decision-making. Comparatively, when John's actions were unintentional, a different circuit of neurons lit up and this action suppressed the amygdala’s response to the graphic language. Effectively, the amygdala was prevented from having input into the decision-making process.

"This is basically a reassuring finding," Marois said. "It indicates that, when the harm is not intended, we don't simply shunt aside the emotional impulse to punish. Instead, it appears that the brain down-regulates the impulse so we don't feel it as strongly. That is preferable because the urge to punish is less likely to resurface at a future date."

Source: Treadway MT, Buckholtz JW, Martin JW, et al. Corticolimbic gating of emotion-driven punishment. Nature Neuroscience. 2014.