Value Computations Underlying Human Proposer Behavior in the Ultimatum Game

Interacting with others to decide how finite resources should be allocated between potentially competing parties is an important part of social life. Considering that not all of our proposals to others are always accepted, the outcomes of such social interactions are probabilistic and risky. Here, we highlight cognitive processes related to value computations in human social interactions, based on mathematical modeling of the proposer behavior in the Ultimatum Game. Our results suggest that the perception of risk is an overarching process across nonsocial and social decision-making domains, whereas the nonlinear weighting of others' acceptance probabilities appears to be more closely associated with social interactive decision-making situations in which others' valuation processes needs to be inferred. Despite the complexity of social interactive decision-making, human participants adjust their risk and probability weighting parameters while interacting with opponents with different social value orientations, and these parameters governing participants' decision-making strategies are influenced by the inferences participants make about their opponents (e.g., how prosocial they think their opponent is relative to themselves), as well as their own social value orientation.