Conformity In An Ultimatum Game

When individuals’ actions are incongruent with those of the group they belong to, they may change their initial behavior in order to conform to the group norm. This phenomenon is known as "social conformity" and refers to the action of changing one’s initial choices or opinions to match those of the group majority. Previous literatures distinguished between informational and normative conformity motivations, the former based on the desire to form an accurate interpretation of reality and behave correctly, and the latter based on the goal of obtaining social approval from others. Traditional economic analyses generally make the simplifying assumption that people are exclusively self-regarding, but there is now a large body of experimental evidence indicating that many people exhibit social preferences, that is, their preferred choices are based on a positive or negative concern for the welfare of others, and on what other players believe about them. This indicates that, in addition to self-interested behavior, people sometimes behave as if they have altruistic preferences, and preferences for equality and reciprocity. Economic theories of social preferences model the motivational forces driving the deviations from economic self-interest in a precise way.We used event-related functional magnetic resonance imaging (fMRI) to investigate brain activity in response to group opinion during an ultimatum game. In the original UG, one player (the proposer) allocates money to himself/herself and to another player (the responder). The responder can either accept or reject the offer. If the responder accepts, both players win their respective amounts, but if the responder rejects, both players receive nothing. The standard economic solution to the Ultimatum Game is for the proposer to offer the smallest sum of money possible to the responder and for the responder to accept this offer, on the reasonable grounds that any monetary amount is preferable to none. However, considerable behavioral research indicates that, irrespective of the monetary sum, modal offers are typically around50%of the total amount. Results have also shown that people reject a high proportion of unfair offers, which would not be adaptive from a rational perspective. The ultimatum game measures whether Responders have a preference in fair.In the present study, we developed a variant of the UG in which participants were asked to decide whether to accept or reject an offer provided by a proposer. After the subject made his/her initial choice, he/she was informed of the choices from four other peers, which could be incongruent, moderately incongruent, or congruent with his/her choice. Then, the participant was given a second opportunity to decide whether to accept or reject the same offer. We predicted that participants would change their choices once they found out that their decisions did not match those of the majority of the group. And we also hypothesized that a conflict with the group opinion would enhance activity in regions involved in norm violations and behavioral adjustment.The interaction between choice and offer type was significant. The result indicated that responses were faster when subjects rejected the fair offers than when they rejected the unfair ones. Regarding the participants’ choices, we found that subjects rejected the unfair offers at a significantly higher rate than the fair offers. In addition, Subjects changed their initial choices at a significantly higher rate in incongruent condition than in congruent condition. Participants changed their initial choices at a significantly higher rate in incongruent condition than in congruent condition, when they rejected the unfair offers in the first decision phase. The interaction between offer type and choice type was significant in several brain regions, including the bilateral insula, medial prefrontal cortex (mPFC), anterior cingulate cortex, precuneus, and bilateral inferior parietal lobule (IPL). Post hoc contrast indicated that these brain regions were activated when participants rejected the fair offers and accepted the unfair offers. The fMRI data in the social influence revealed that the difference between incongruent condition and baseline condition (no information) induced activation in bilateral insula, middle temporal gyrus (MTG), bilateral middle frontal gyrus (MFG), bilateral IPL, mPFC, and precuneus. Comparison of activity in congruent condition with baseline condition showed significantly greater activation in bilateral superior parietal lobule (SPL) and superior frontal gyrus (SFG) when participants viewed congruent peers’ choice. And we also compared neural activity in the incongruent condition and congruent condition. Incongruent condition activated the mPFC. Then, we compared the incongruent trials which subjects changed their initial choices with the trials which subjects didn’t change their initial choices. The result showed that the neural activity in the insula, bilateral MFG, mPFC, bilateral IPL, and midbrain elicited by the social conflict following conformity were stronger than the activity elicited by the social conflict following non-conformity. Finally, the neural activity in the medial frontal gyrus was higher for unfair-reject-incongruent condition.These findings contribute to recent research examining neural mechanisms involved in detecting violations of social norms, and provide information regarding the neural representation of conformity behavior in an economic game. The mechanisms underlying social conformity may be similar to those implicated in behavioral adjustments. Considering the social implications of an unfair offer, one possible explanation is that individuals’ group identification increased when they believed that they have been treated unfairly. This strong group identification motivated individuals to take the viewpoints of the other group members, change their initial choices, and conform to group norms. The other possible explanation is that the incongruent-fair condition contains two social norms that conflict with each other (accept the fair offer versus conform to group opinions). This would make the conformity effect in the incongruent-fair condition easier to resist. Participants were more likely to conform to others’ behavior in the incongruent-unfair condition, because the incongruent-unfair condition presents the "conform to group opinion" norm more directly. Such reasoning is also consistent with the behavioral result that participants changed their initial choices when their initial choices were incongruent with the group opinion in unfair offer scenarios.