Abstract: “Health behaviors such as drinking, smoking, and physical activity can be influenced by peers’ behaviors1. Oftentimes, peer habits and norms shape others’ behavior implicitly, even in the absence of any peer explicitly attempting to influence behavior2. However, little is known about how the brain tracks information about the health behaviors of others and represents this information in daily life.

The current investigation builds on this work by investigating how the brain represents the health habits of peers and supports the ability to take the perspective of peers who vary in their health habits, such as their consumption of alcohol. We will use multivoxel pattern analysis (MVPA) to ask the following questions: (1) How does the brain encode information about peer drinking habits first when explicitly thinking about peers who drink more vs. less than oneself? (2) Second, does the brain evoke information about a peer’s drinking habits outside of a drinking context, even when individuals are not instructed to think about the health behavior of their peers? And to what degree is this neural representation shared across individuals vs. idiosyncratic? (3) Finally, is the degree to which one’s brain evokes information about peer drinking habits spontaneously associated with how they respond to pro-drinking influences outside the lab? Answering these questions may provide insight into how individuals process information about others more generally and respond to health-related peer influence outside the laboratory. Moreover, this investigation provides an opportunity to bridge traditional health behavior theories (e.g., about social norms and social learning) with models of the social brain to predict individual differences in susceptibility to social influence.

Current study The main goals of the study are threefold. First, we test (1) how the brain encodes information about peers who drink more or less than oneself during explicit alcohol-related perspective-taking, and (2) whether the brain evokes this neural information (specific to peers drinking habits), in a more naturalistic context, such as when viewing peer faces. Next, IF WE ARE ABLE TO XX., we WILL examine (3) whether individuals whose brains express information about peer drinking habits more strongly when viewing peer faces are also more susceptible to pro-drinking conversational influences in their daily lives. To examine these questions, we will combine data from two different fMRI tasks and behavioral data collected via mobile diaries completed by the same participants. Participants included 34 college students who were part of 10 existing social groups, recruited across two campuses.

In the first task, which we will refer to as the “face-viewing” task, participants passively viewed the faces of around 25 peers from their social group. In the second “perspective-taking” fMRI task, participants were asked to respond to images of alcoholic beverages by taking the perspective of four target peers: two of whom they previously described to drink more alcohol than they did, and two of whom they described to drink less than they did. The target peers in the perspective-taking task were also referenced in the faces task. As part of the protocol, participants completed the face-viewing fMRI task first and the perspective-taking task second to avoid potential alcohol-related priming when passively viewing peer faces.”