Social equality in the number of choice options is represented in the ventromedial prefrontal cortex.
A distinct aspect of the sense of fairness in humans is that we care not only about equality in material rewards but also about equality in nonmaterial values. One such value is the opportunity to choose freely among many options, often regarded as a fundamental right to economic freedom. In modern developed societies, equal opportunities in work, living, and lifestyle are enforced by antidiscrimination laws. Despite the widespread endorsement of equal opportunity, no studies have explored how people assign value to it. We used functional magnetic resonance imaging to identify the neural substrates for subjective valuation of equality in choice opportunity. Participants performed a two-person choice task in which the number of choices available was varied across trials independently of choice outcomes. By using this procedure, we manipulated the degree of equality in choice opportunity between players and dissociated it from the value of reward outcomes and their equality. We found that activation in the ventromedial prefrontal cortex (vmPFC) tracked the degree to which the number of options between the two players was equal. In contrast, activation in the ventral striatum tracked the number of options available to participants themselves but not the equality between players. Our results demonstrate that the vmPFC, a key brain region previously implicated in the processing of social values, is also involved in valuation of equality in choice opportunity between individuals. These findings may provide valuable insight into the human ability to value equal opportunity, a characteristic long emphasized in politics, economics, and philosophy.
Tamagawa University Brain Science Institute, 6-1-1, Tamagawa-gakuen, Machida, Tokyo 194-8610, Japan, Japan Society for the Promotion of Science, 5-3-1, Koji-machi, Chiyoda-ku, Tokyo 102-8471, Japan, Division of the Humanities and Social Sciences, California Institute of Technology, Pasadena, California 91125, Department of Psychology, University of California Los Angeles, Los Angeles, California 90095, and Department of Cognitive and Behavioral Science, University of Tokyo, 3-8-1, Komaba, Meguro-ku, Tokyo 153-8902, Japan.
Ryuta
R
Aoki
Madoka
M
Matsumoto
Yukihito
Y
Yomogida
Keise
K
Izuma
Kou
K
Murayama
Ayaka
A
Sugiura
Colin F
CF
Camerer
Ralph
R
Adolphs
Kenji
K
Matsumoto
D001931:Brain Mapping; D002755:Choice Behavior / Q000502:physiology*; D004644:Emotions; D005260:Female; D005717:Games, Experimental; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D017397:Prefrontal Cortex / Q000098:blood supply / Q000502:physiology*; D012054:Reinforcement, Psychology; D012938:Social Perception; D013997:Time Factors; D055815:Young Adult
D010100:Oxygen
neuroeconomics; reward system; social comparison