Our stomachs are bad at math, and what’s more, we get no help from our attention or our memory. We have a difficult time remembering the amount we have eaten; we don’t register whether we ate 20 French fries or 30. It gets even worse when we are out dining with our friends and family. Five minutes after dinner, 31% of the people leaving an Italian restaurant could not remember how much bread they ate, and 12% of the bread eaters denied having eaten any bread at all.
If we could see what we ate we would probably eat less. Unfortunately, all that remains of most foods is an empty plate. However, chicken wings are different; after we finish a chicken wing, the bony evidence remains. This gave my graduate students and me an idea. Usually when people are given all of the chicken wings they can eat, the bones are continuously bussed and we lose track of how much we have eaten. If people could see the remains of what they had eaten, would they eat less?
On a Super Bowl Sunday in 2001, we invited 77 MBA students to a party at a local sports bar to test our idea. After ordering what they wanted to drink, these students took all the wings they wanted and returned to their tables. When they finished their chicken wings, they could pile up the bones in the empty bowls that were on their table.
The waitresses were working with us, and instructed to bus the leftover chicken bones from only half of the tables. They bused these tables three or four times, leaving an empty bowl in which to put any future bones. When they brought the bones back to the kitchen, they told us which table each bowl came from. We then counted (and weighed) the number of leftover bones to determine how much the average person at that table had eaten. For the tables which were not bussed, the waitresses could take drink orders, but we asked them to leave the bones on the tables. After the game was over and the MBA students had left, we went over to these tables and counted the bones.
The results were predictable. If people had their tables continually bused, they continually ate. For the clear-table group, each person ate an average of seven chicken wings. The individuals at the bone pile tables ate an average of two fewer chicken wings. This was 28% less than those whose tables had been bused.
Our stomach cannot count and we do not remember. Unless we can actually see what we are eating, we can very easily overeat.