To investigate whether social influences cause increases in eating behavior, thirty undergraduate psychology students completed a diet diary for three 5-day periods. Subjects were instructed to either eat alone or eat with other people, actively eating with them for two of these periods. For the third period, subjects were instructed to eat as they normally would (with or without other people present). When instructed to eat with others present, subjects overall consumed more food, water, sodium, and alcohol than when they were instructed to eat alone. In the normal condition, food intake was 60% higher when the subjects ate with others present than when they ate alone. These results suggest that social facilitation has a causal influence on eating which increases food intake.