structural:expansion, structural:summarization
Neural mechanisms

From a neurological perspective, the medial prefrontal cortex (mPFC) and the striatum play an important role in figuring out the value of specific actions. The mPFC is active when determining "socially tagged" objects, which are objects that peers have expressed an opinion about; the striatum is significant for determining the value of these "socially tagged" objects and rewards in general. An experiment performed by Mason et al. utilizing fMRI scans analyzed individuals who were assigned to indicate if a chosen symbol appeared consecutively. The researchers did not tell the subjects the real purpose of the experiment, which was to collect data regarding mPFC and striatum stimulation. Before the actual experiment began, the subjects were subject to a phase of "social" influence, where they learned which symbols were preferred by other subjects who had completed the experiment (while in actuality these other subjects did not exist). Mason et al. found that determining an object's social value/significance is dependent on combined information from the mPFC and the striatum. Without both present and functional, it would be difficult to determine the value of action based upon social circumstances.

A similar experiment was conducted by Stallen, Smidts, and Sanfrey. Twenty-four subjects were manipulated using a minimal group paradigm approach. Unbeknownst to them, they were all selected as part of the "in-group", although there was an established "out-group". Following this socialization, the subjects estimated the number of dots seen on the screen while given information about what an in-group or out-group member chose. Participants were more likely to conform to in-group decisions as compared to out-group ones. The experiment confirmed the importance of the striatum in social influence, suggesting that conformity with the in-group is mediated with a fundamental value signal—rewards. In other words, the brain associates social inclusion with positive reward. The posterior superior temporal sulcus (pSTS), which is associated with perspective taking, appeared to be active as well, which correlated with patients' self-reports of in-group trustworthiness.

In adolescence, risk-taking appears to increase dramatically. Researchers conducted an experiment with adolescent males who were of driving age and measured their risk-taking depending on whether a passenger (a peer of the same age) was in the car. A driving simulation was created, and certain risky scenarios, such as a decaying yellow light as the car was approaching, were modeled and presented to the subjects. Those who were most likely to take risks in the presence of peers (but took fewer risks when there were no passengers) had greater brain activity in the social-cognitive and social-affective brain systems during solo activity (no passengers.) The social-cognitive aspect refers to the ability to gauge what others are thinking and is primarily controlled by the mPFC, right temporal parietal junction, and the posterior cingulate cortex. The social-affective aspect relates to the reward system for committing actions that are accepted or rejected by other people. One side of the reward system is "social pain", which refers to the emotional pain felt by individual due to group repudiation and is associated with heightened activity in the anterior insula and the subgenual anterior cingulate cortex.