Graphic descriptions of intentionally harmful acts boost brain activity in the amygdala - a region involved with processing emotions - and strengthen its connectivity with the lateral prefrontal regions, which are involved in decision-making. These findings, reported this week in Nature Neuroscience, reveal a mechanism by which emotional reactions and measured decision-making interact when people decide on the severity of punishment appropriate for harmful actions.
Two factors can influence people's punishment decisions: instinctive, emotional reactions and intellectual assessments. Previous studies report that punishment decisions vary based on whether the act is perceived as purposeful or not, but the neuronal basis for this has been unknown.
Michael Treadway and colleagues used functional magnetic resonance imaging (fMRI) to track brain activity while people decided how much punishment to give someone involved in an accidentally or intentionally harmful scenario, such as property damage or death. Half of these scenarios were objectively described, while the other half were graphically described.
The authors found higher punishment ratings for the vividly described scenarios, but only in the intentionally harmful cases. In these, the fMRI activity in participants' amygdala was greater as was the connectivity activity between the amygdala and the dorsolateral prefrontal cortex. In contrast, participants meted out more moderate punishment for the unintentionally harmful behavior. In these cases, the authors report greater connectivity between the amygdala and the dorsal anterior cingulate cortex, which is involved in working out the mental states of others. The authors suggest that the two different patterns of connectivity found may explain the emotional component of punishment decisions, and why sometimes people decide on harsher punishments.