How do we judge when to stop eating?

Brian Wansink has a lab where he tests how people decide how much to eat.

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.

Just now I didn't eat a cookie biscuit in the work kitchen because the packet was in a plastic bag. When I moved to the US I was very confused by those offers where you get a quart of coke for only 20 cents more. According to the article a lot of companies are now trying to use Dr. Wansink's ideas for good, not evil (because it's better for them in the long run).