Time spent in conversation over meals predicts default network function: Evidence from a passive mobile-sensing and fMRI study.

Sharing meals with others, often referred to as commensality, fosters social connection and may have been essential to human brain evolution. Here, we investigate whether shared meals impact social brain processes through the conversations they afford. If so, then time spent in conversation over meals should affect the default network- a set of interconnected cortical regions reliably associated with the social exchange of ideas. To test this possibility, we combined passive-mobile sensing with neuroimaging. Undergraduate participants had an application on their smartphone for two months that unobtrusively captured their time spent in conversation, as well as their location on and around campus. In between these two months, participants completed a resting state scan. Time spent in conversations around meals (e.g., at cafeterias and restaurants) during the prior month predicted greater functional connectivity in the dorsomedial default network subsystem, specifically between the left inferior frontal gyrus (LIFG) portion and the rest of the subsystem regions. This relationship was preferential to: (1) time spent in conversation over the past (vs. future) month, (2) connectivity with the LIFG (vs. other dorsomedial subsystem nodes), (3) the dorsomedial subsystem (vs. other default network subsystems), (4) eateries (vs. other locations), and (5) time spent around conversation at eateries, rather than time at eateries more generally. Follow-up analyses further revealed results were driven by a ventral portion of the LIFG, with peaks in voxel-connectivity associated with language, social, memory, and affective processes, as determined by the meta-analytic platform, NeuroSynth. Time spent in conversation over meals may exercise social cognitive processes supported by the dorsomedial subsystem, a network key to social communication, understanding, and connection.