Comparison of activity during judgments of sympathy, and sentence reduction, suggest that activity in DMPFC (also known as paracingulate), precuneus (also known as posterior cingulate) and TPJ reflect a judgment-action circuit, which is illustrated in . Strength of sympathy judgments is associated with activity in DMPFC, precuneus and TPJ. DMPFC is involved in general mentalising11
and is active when empathizing12
with others in pain. Precuneus has been linked to subjective perspective taking14
. TPJ is also commonly identified as a part of a theory-of-mind circuit17
, including mentalising about intentions18
, and was activated in one study on judging innocence of intentions of people who caused harm19
. This suggests that the sympathy judgment is an engagement with a reasoned simulation of what the defendant was thinking when committing the crime or how most people would judge the normative basis for mitigation. Note that although precuneus and TPJ can each be activated by non-social demands as well (for example, attention reorienting20
), they are rarely co-activated as a group unless social cognitive demands are present.
Regions activated by the punishment reduction judgment include a large region of precuneus and smaller regions in DMPFC and ACC. As noted, precuneus has been linked to simulation on the self to understand others, and is also active when compassionating21
and forgiving others22
. The activation in this area is correlated with more iterated steps23
strategic thinking in game theory tasks. Note that both feelings of sympathy and judged mitigation of punishment were encoded in activity in precuneus. This overlapping activity suggests that the precuneus may be a region that accepts emotional judgment input and maps it into concrete punishment actions.
ACC is a region now thought to be activated by negative affect25
, positive reward27
and cognitive control26
. In our context, mapping emotional sympathy into numerical sentencing requires high-level executive function by weighing negative affective reaction to murder, positive sympathy for the murder's mitigating circumstances and exerting cognitive control to choose numerical punishments that weigh these emotions consistently.
Smaller regions in caudate also showed differential activation in response to punishment reduction (Supplementary Table S2
). Caudate activity is consistent with the hypothesis that sentence reduction is encoded as a special kind of prosocial 'charity' (as mitigation is like giving to charity29
), as other prosocial choices activate the caudate too30
One fMRI study elicited punishment judgments in artificial scenarios varying offender culpability6
and reports right DLPFC activity associated with responsibility judgments. We speculate that the absence of right DLPFC activation in our study is because there is no doubt about the defendants' guilt, so the most morally burdensome question of guilt versus innocence is resolved (right DLPFC is discharged from jury duty, so to speak). Activity then shifts to areas generally associated with moral and cognitive conflicts instead (DMPFC, precuneus and ACC).
The individual difference analysis showed that activity in the right mid-insula was related to the individual differences on the inclination to mitigate (mapping sympathy to sentences). Middle/posterior insula has been suggested to encode economic inequity31
, norm violation32
, somatosensory representation33
, monitoring internal states34
and heart rate during a compassionate state35
. These types of interoceptive processing in middle insula suggest that it is sensitive to emotions linked to sociality. Our study provides unusual evidence of this processing associated with a unique high-impact social judgment that affects others.
The identified brain activity provides new insight into the capacity of the average brain to translate sympathetic feelings into appropriate legal action. A plausible neuro-legal standard is that the influence of sympathetic reaction on difficult sentencing should recruit brain areas that process sympathy judgments in general, as well as areas that encode difficult decision conflict. Activity in these 'sympathy' regions is evident in our study when judging sympathy alone, and in choosing sentence mitigation. However, not every brain maps sympathy to prison sentences in the same numerical way (as reflected in differential mid-insula activity). Differences in these brain circuits between individuals, suggest that differential juror responses might need to be considered unequally. There is also mixed evidence about the normative basis of legal judgment, including a recent finding that judges' decisions are affected by timing of meals36
The current finding would also contribute to the attribution literature on situational correction, as there has not been any fMRI work on this. People often attribute behaviour to the corresponding personal disposition, which is, yet, corrected based on situational inducements too37
. This is an apt psychological function behind mitigating circumstances that is to make someone less culpable, and the revealed brain activity might be associated with this type of situational correction.
Finally, we note that many legal principles treat emotional responses as likely to be prejudicial and prone to inflammatory manipulation (that is, an ideal juror would suppress them and legal rules limit their influence). Weighing mitigating circumstances during sentencing (after
a verdict) represents an unusual case in which emotional sympathy judgment is actually required. Japanese criminal law, for example, requires that the decision among these sentences be based on mitigating circumstances38
Ironically, the fact that sympathy is clearly evident in brain activity, and influences sentence mitigation (as it should), raises interest in the opposite question: can people also suspend emotions when the law instructs them to? More generally, a deeper understanding of the brain could help figure out how highly evolved brain structures, which were sculpted to maintain order in small-scale ancestral societies, can be put to work under modern legal rules in much more challenging cases to create modern justice.