What the subjects didn’t see, however was that the soup bowl was rigged up to system of unseen tubes and valves that let the experimenters covertly add or take away soup as people ate. Some subjects ate an amount of soup equal to what they were presented with (either the small or the large portion), but others ate a different amount from what they saw. In these ‘incongruous’ cases, people thought they consumed the large portion, but really ate the small portion, or vice versa. With this setup, the experimenters could then test how hungry the subjects were some time later, and tease apart the purely physiological aspects of hunger (having to do with the volume consumed) from the cognitive aspects of hunger (having to do with impressions and judgments about what was consumed).
The first result is that there’s no fooling your stomach immediately after a meal. When tested shortly after eating the soup, subjects who had eaten the larger portion were more sated than those who had eaten the smaller portion, and it mattered comparatively little how much people thought they ate. Two cups is more than one cup, and your stomach gets it right, despite any visual trickery.
Two and three hours after eating, however, a different sort of pattern emerged. The subjects were all hungrier, of course, but their hunger had little to do with the volume of soup they had actually eaten. Instead, it was what they remembered seeing in the bowl that mattered. In fact, those who ate the small portion and thought it was large were more sated than those who ate the large portion and thought it was small. When it comes to the feeling of fullness, the eyes are more important than the stomach.
Overall, this work helps clear up our thinking on an important component of hunger that’s historically been tough to study. Of course, this doesn’t say that hunger is the same thing as a memory of having eaten (or rather, having not eaten). Just that our drive to eat can be biased by memory, as well as possibly the contexts in which we encounter food. On the practical front, this work also opens the door for some possible cognitive-based approaches to dieting. Memory is notoriously fickle, and we may be able to use this to our advantage to enhance our feelings of fullness. In fact, previous work has already suggested that distracted, or “mindless” eating leads people to feel hungry, while more deliberate and mindful eating leads people to feel full. One possibility is that deliberative eating leads to stronger food-associated memories, in turn providing a stronger antidote against future hunger.
So when you sit down for your next meal, pay close attention and remember what you eat – you may pull off that New Year’s resolution yet.
Are you a scientist who specializes in neuroscience, cognitive science, or psychology? And have you read a recent peer-reviewed paper that you would like to write about? Please send suggestions to Mind Matters editor Gareth Cook, a Pulitzer prize-winning journalist at the Boston Globe. He can be reached at garethideas AT gmail.com or Twitter @garethideas.