People entering the movies were given a bucket of either just-popped, fresh popcorn or stale, week-old popcorn. Moviegoers who didn’t usually eat popcorn at the movies ate much less stale popcorn than fresh popcorn. Moviegoers who typically had popcorn at the movies ate about the same amount — regardless it was fresh or stale. When we’ve repeatedly eaten a food in an environment, our brain comes to associate the food with that environment and we keep eating as long as those environmental cues are present.
Personality and Social Psychology Bulletin, 2011