Abstract
OBJECTIVE: Health-related norms in social networks can influence whether people are open to health behavior change. Yet, little is known about how social networks relate to the ways individual brains respond to persuasive health messaging. The current study focuses on ventromedial prefrontal cortex (VMPFC) activity as an index of neural receptivity to health messages that may be related to behavior change. The study tested whether health-related norms and perceived physical activity levels within participants' social networks are associated with neural receptivity to health messages. METHOD: Adults who initially reported under 200 minutes/week of physical activity (N = 146) rated the perceived physical activity levels of, and closeness to, each person in their core social network. VMPFC activity was monitored using fMRI while participants viewed persuasive health messages promoting physical activity. Longitudinal changes in sedentary behavior were objectively logged using wrist-worn accelerometers throughout a 2-week baseline and the month following the fMRI scan. RESULTS: Higher levels of perceived physical activity in participants' social networks were associated with greater VMPFC activity during message exposure, which in turn were associated with greater decreases in sedentary minutes. By contrast, greater closeness to physically inactive social ties was associated with lower VMPFC activity. CONCLUSIONS: Perceived norms in social networks relate to neural receptivity to health messaging. In particular, closeness to physically inactive ties is associated with lower neural receptivity to health messages encouraging physical activity, which may undermine the effectiveness of health messages. (PsycInfo Database Record (c) 2021 APA, all rights reserved).