Social facilitation of the spontaneous meal size of humans occurs regardless of time, place, alcohol or snacks.

The amount eaten by humans in spontaneously ingested meals is positively correlated with the number of other people present. This could be due to a social facilitation or may be produced as an artifact of a covariation produced by a third factor. Possible covariations produced by time and location of eating, alcohol intake, and snack/meal ingestion were investigated by paying 78 adult humans to maintain 7-day diaries of everything they ingested, when and where they ingested it, and the number of other people present. The results demonstrate that, although the covariances exist, they could not account for the social correlation. Strong, positive and significant correlations between meal size and the number of other people present were found separately for meals eaten during the breakfast period, the lunch period and the dinner period, eaten in restaurants, at home and elsewhere, eaten accompanied by alcohol intake or without alcohol, and for only snacks or only meals. The results suggest that the correlation results from a true social facilitation of eating and that this facilitation is an important determinant of eating regardless of whether alcohol is ingested with the meal, a snack or a meal is eaten and regardless of when or where it is eaten.