Neural circuits in the brain that are activated when mitigating criminal sentences

Abstract

In sentencing guilty defendants, jurors and judges weigh 'mitigating circumstances', which create sympathy for a defendant. Here we use functional magnetic resonance imaging to measure neural activity in ordinary citizens who are potential jurors, as they decide on mitigation of punishment for murder. We found that sympathy activated regions associated with mentalising and moral conflict (dorsomedial prefrontal cortex, precuneus and temporo-parietal junction). Sentencing also activated precuneus and anterior cingulate cortex, suggesting that mitigation is based on negative affective responses to murder, sympathy for mitigating circumstances and cognitive control to choose numerical punishments. Individual differences on the inclination to mitigate, the sentence reduction per unit of judged sympathy, correlated with activity in the right middle insula, an area known to represent interoception of visceral states. These results could help the legal system understand how potential jurors actually decide, and contribute to growing knowledge about whether emotion and cognition are integrated sensibly in difficult judgments.

Figure 1. Task design and behavioural performance.

(a) Study paradigm. (b) Mean punishment ratings for sympathy and no-sympathy trials (n = 22, paired t-test, t₂₁=−18.94, P<0.001). (c) Mean sympathy ratings for sympathy and no-sympathy trials (n = 22, paired t-test, t₂₁=11.82, P<0.001). (d) Correlation between sympathy and punishment ratings for sympathy stories (red circles) and no-sympathy stories (green circles). Error bars indicate s.d.

Figure 2. Brain regions activated during trial-by-trial sympathy and punishment reduction.

Regions in which activity correlated with parametric regressors of increasing sympathy (green) and reduced punishment (red). Common areas were found in precuneus (yellow). The image is shown at P<0.001 (uncorrected; n = 22, one-sample t-tests).

Figure 3. Individual differences in inclination towards mitigation.

Activation in right middle insula in the contrast sympathy minus no-sympathy trials (a, MNI 34/−8/12; n = 22, one-sample t-test, P=0.023, small-volume-corrected) correlated with participant-wise coefficient of mitigation (b, n = 22, Pearson r=−0.62, P=0.002).