When I hand my one-year-old son something to eat, he spends a short time looking at it and a long time looking at me: Is this good? Is it tasty? Is this what we eat? The answer (olive from me, yes; bug from floor, no) has a bit to do with the chemical and physiological process of perceiving the thing in his mouth. But it has much more to do with the social and psychological process of his relationships to people, places and the repeated cause-and-effect of daily life. Which fact is the theme of this study. It found people eating lousy food without thought or hesitation when it appeared in a familiar and expected setting. A slight change in the habitual circumstances, though, is apparently enough to make people notice the crappiness they'd otherwise ignore.

The study, by David T. Neal, Wendy Wood, Mengju Wu and David Kurlander, used a setting in which many Americans eat mindlessly: A movie theater. The researchers gave moviegoers in a Los Angeles theater free buckets of popcorn. Some were nice and fresh. But others were a week old and pretty obviously stale. After the film, people from the audience answered a few questions about how hungry they had been coming in, and about their eating habits at the movies. Meanwhile, the researchers measured how much they had eaten.

According to the paper, in this month's issue of Personality and Social Psychology Bulletin, a lot of people accepted the gift—hey, free popcorn!—but not all were in the habit of eating while watching a film. This turned out to be important: People who said they usually ate popcorn at the movies ate about the same amount, no matter what they had received. It didn't matter if their food was stale or fresh. But people who didn't typically get popcorn with their movie ate far less of the stale stuff. (The effect held no matter how hungry they had been before the movie.)

Interestingly, it turned out that this effect only held in the theater. When the same procedure was run on people gathered to watch movie clips in a meeting room, nobody ate much stale popcorn. The habitual popcorn-eaters didn't fall into their automatic behavior, suggesting that the cue wasn't just the activity of movie-going but also the place.

Neal et al. also found that this kind of automatic eating is easily disrupted. In a second experiment, they once again handed out their popcorn buckets at a movie theater. But this time, they asked some of the recipients to eat with their non-dominant hand. That allowed them to compare two kinds of habitual popcorn-at-the-movies types: Those who had eaten as usual and those who had eaten in an odd, attention-demanding way. Result: Those who had to eat with their non-dominant hand apparently noticed when their food was soggy and cold. They ate less stale popcorn.

The fundamental point here probably isn't news to the advertising firms and marketers that work hard to create a sense that their products and restaurants are "a familiar, comfortable place," as this analysis of McDonald's marketing in India puts it. But it might give comfort to people worried about obesity and unhealthy foods to know that this kind of habit-building is rather easily derailed.

From my post-rational perspective, it's one more piece of evidence against the assumption that people have stable preferences, which they understand and act upon consistently. The standard model, after all, is still that consumers place a certain value on popcorn—not that the value depends on where they're sitting or which hand they're using to eat.

Illustration: "A bucket of delicious-looking purple worms ('sand worms' from Beihai, to be killed on demand') at a street vendor in Guangzhou." From Wikimedia.

Neal, D., Wood, W., Wu, M., & Kurlander, D. (2011). The Pull of the Past: When Do Habits Persist Despite Conflict With Motives? Personality and Social Psychology Bulletin DOI: 10.1177/0146167211419863