The following example can be used simply to illustrate creative research design but can also be useful in a section or course on motivation to illustrate the role of memory in influencing people’s decisions about when to start and stop eating. Suppose you have just finished a big lunch at your favorite restaurant when a server gets mixed up and brings you another plate of that same lunch that was meant for someone else. You would almost certainly send it away, but why? Decisions to start eating or stop eating are affected by many biological factors, including signals from your blood that tell your brain how much “fuel” you have available, but Paul Rozin and his colleagues were interested in how these decisions are affected by psychological factors, such as being aware that you have already eaten. What if you didn’t remember that you had just had lunch? Would you have started eating that second plate of food?

To explore this question, Rozin conducted a series of tests with R.H. and B.R., two men who had anterograde amnesia, a kind of brain damage that left them unable to remember anything for more than a few minutes. The men were tested individually, on three different days, in a private room where they sat with a researcher at lunchtime and were served a tray of their favorite food. Before and after eating, they were asked to rate their hunger on a scale from 1 (extremely full) to 9 (extremely hungry). Once lunch was over, the tray was removed, and the researcher continued chatting, making sure that each man drank enough water to clear his mouth of food residue. After ten to thirty minutes, a hospital attendant reentered with an identical meal tray and announced “Here’s lunch.” These men had no memory of having eaten lunch already, but would signals from their stomachs or their blood be enough to keep them from eating another one?

Apparently not. In every test session, R.H. and B.R. ate all or part of the second meal and, in all but one session, ate at least part of a third lunch that was offered to them ten to thirty minutes after the second one. Rozin conducted similar tests with J.C. and T.A., a woman and a man who had also suffered brain damage but who still had normal memory for recent events. In each of two test sessions, these people finished their lunch but refused the opportunity to eat a second one. These results suggest that the memory of when we last ate can indeed be a factor in guiding decisions about when to eat again. They also support the conclusion that eating is controlled by a complex combination of biological, social, cultural, and psychological factors. As a result, we may eat when we think it is time to eat, regardless of what our bodies tell us about our physical need to eat.

[Reference: Rozin, P., Dow, S., Moscovitch, M., & Rajaram, S. (1998). The role of memory for recent eating experiences in onset and cessation of meals. Evidence from the amnesic syndrome. Psychological Science, 9, 392–396.]