Although people think they make 15 food decisions a day on average, his research shows the number is well over 200. Some are obvious, some are subtle. The bigger the plate, the larger the spoon, the deeper the bag, the more we eat. But sometimes we decide how much to eat based on how much the person next to us is eating, sometimes moderating our intake by more than 20 percent up or down to match our dining companion.

Much of his work is outlined in the book “Mindless Eating: Why We Eat More Than We Think” (Bantam), which will be published on Tuesday. The book is his fourth over all, but his first directed at a general audience. It is peppered with his goofy, appealing Midwestern humor and practical diet tips. But the most fascinating material is directly from his studies on university campuses and in test kitchens for institutions like the United States Army.

An appalling example of our mindless approach to eating involved an experiment with tubs of five-day-old popcorn. Moviegoers in a Chicago suburb were given free stale popcorn, some in medium-size buckets, some in large buckets. What was left in the buckets was weighed at the end of the movie. The people with larger buckets ate 53 percent more than people with smaller buckets. And people didn’t eat the popcorn because they liked it, he said. They were driven by hidden persuaders: the distraction of the movie, the sound of other people eating popcorn and the Pavlovian popcorn trigger that is activated when we step into a movie theater.

Dr. Wansink is particularly proud of his bottomless soup bowl, which he and some undergraduates devised with insulated tubing, plastic dinnerware and a pot of hot tomato soup rigged to keep the bowl about half full. The idea was to test which would make people stop eating: visual cues, or a feeling of fullness.

People using normal soup bowls ate about nine ounces. The typical bottomless soup bowl diner ate 15 ounces. Some of those ate more than a quart, and didn’t stop until the 20-minute experiment was over. When asked to estimate how many calories they had consumed, both groups thought they had eaten about the same amount, and 113 fewer calories on average than they actually had.

Last week in his lab seven people were finishing lunch while watching a big-screen TV. Cartoons on the TV served as a distraction so participants would not be influenced by what and how much those nearby ate.