Georgio Coricelli of the USC Dornsife College of Letters, Arts and Sciences led a multinational team of researchers that measured activity in the regions of the brain associated with rewards and with social reasoning while participants in the study entered in lotteries.

Their study appears in the Proceedings of the National Academy of Sciences.

The researchers found that the striatum, a part of the brain associated with rewards, showed higher activity when a participant beat a peer in the lottery, as opposed to when the participant won while alone. The medial prefrontal cortex, a part of the brain associated with social reasoning, was more activated as well. Those participants who won in a social setting also tended to engage in more risky and competitive behavior in subsequent lotteries.

"These findings suggest that the brain is equipped with the ability to detect and encode social signals, make social signals salient, and then, use these signals to optimize future behavior," Coricelli said.

As Coricelli explained, in private environments, losing can more easily be life-threatening. With no social support network in place, a bad gamble can spell doom.

In group environments, on the other hand, rewards tend to be winner-takes-all. Nowhere is this more clear than in sexual competition, where -- to borrow a phrase from racing legend Dale Earnhardt, Sr. -- second place is just first loser.

"Among animals, there are strong incentives for wanting to be at the top of the social ranking," Coricelli said. "Animals in the dominant position use their status to secure privileged access to resources, such as food and mates."

The research was supported by the Human Frontier Science Program, the Fondation pour la Recherche Medicale, the National Science Foundation, and the Agence Nationale de la Recherche and Provincia Autonoma de Trento.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Southern California, via EurekAlert!, a service of AAAS.

 

Journal Reference:

1. N. Bault, M. Joffily, A. Rustichini, G. Coricelli. Medial prefrontal cortex and striatum mediate the influence of social comparison on the decision process. Proceedings of the National Academy of Sciences, 2011; DOI:10.1073/pnas.1100892108
    

Abstract

We compared private and social decision making to investigate the neural underpinnings of the effect of social comparison on risky choices. We measured brain activity using functional MRI while participants chose between two lotteries: in the private condition, they observed the outcome of the unchosen lottery, and in the social condition, the outcome of the lottery chosen by another person. The striatum, a reward-related brain structure, showed higher activity when participants won more than their counterpart (social gains) compared with winning in isolation and lower activity when they won less than their counterpart (social loss) compared with private loss. The medial prefrontal cortex, implicated in social reasoning, was more activated by social gains than all other events. Sensitivity to social gains influenced both brain activity and behavior during subsequent choices. Specifically, striatal activity associated with social gains predicted medial prefrontal cortex activity during social choices, and experienced social gains induced more risky and competitive behavior in later trials. These results show that interplay between reward and social reasoning networks mediates the influence of social comparison on the decision process.