In a recent series of experiments, Jennifer K. MacCormack, a doctoral candidate in psychology and neuroscience at the University of North Carolina, Chapel Hill, found that people describe themselves, when hungry, as more annoyed than usual and less in control of their emotions. But that behavior arose only in specific circumstances, and only in comparison to peers who had recently eaten, Ms. MacCormack found.

In one study, she tested the patience of more than 230 hungry student participants by deliberately but discreetly crashing their computers when they were in the middle of a tedious task. That frustration alone was not enough to get a rise out of the hungry students. Ms. MacCormack had divided the subjects into two groups, one that focused on their emotional state as they worked on the computer and another that did not. Only the individuals in the second group, presumably less self-aware of their growing agitation, showed clear signs of stress and annoyance when the computer crashed.

“Being hungry clearly does change our affect, our emotional state,” Ms. MacCormack said. “But this evidence suggests that it does not automatically lead to being angry or more selfish.”