Moral and visual choices follow similar rules in different brain patterns
A peer-reviewed experiment asked 53 volunteers to make moral and visual choices using identical pictures. Both tasks fitted the same model of evidence accumulation, yet brain activity linked to difficult choices differed between them. Holding the images and response movements constant helped separate the tasks, while the young university sample limits how widely the findings apply.
Science··Midday
Identical images carried two different choices
A choice between two pictures can involve judging their size or the seriousness of the behaviour they depict. Researchers used that contrast with 53 healthy, right-handed volunteers recruited from universities in Zurich. Participants first rated the pictures, then alternated between moral and visual tasks during functional magnetic resonance imaging, which measures changes associated with brain activity. The peer-reviewed experiment kept the response movement the same.[1]
One decision model fitted both tasks
Pictures were prepared so that their moral ratings and displayed area varied independently. Bringing alternatives closer on the relevant dimension made decisions more difficult, affecting speed and accuracy. Four computational models were compared. The best-fitting one used a fixed decision threshold with an evidence-accumulation rate that changed with conflict, describing the behaviour in both tasks.[1]
Brain responses separated the two kinds of conflict
Similar behaviour did not correspond to identical neural patterns. Moral conflict increased activity in the right posterior temporoparietal junction, where temporal and parietal brain regions meet, and in some prefrontal areas. Visual conflict involved other locations and sometimes opposite response directions. Activity associated with response time was more widely shared. The young university sample and tasks concerning blameworthy or neutral behaviour restrict the comparison: everyday morality and moral praise were not measured.[1]
