Larger portions of food cause people to eat more. Anyone who has eaten at Chili’s and observed the girth of their clientele already knows this. Related: I remember seeing some research that showed as the size of an HTML textarea increases, the more words people write in it. (via mr)
Update: A self-refilling soup bowl experiment suggests that “visual cues of portion size may influence intake”. (thx, justin) Also, adding lanes to heavily traveled roadways increases traffic; that is, supply increases demand.