The ladies who lunch do not obsess about their weight in the rhesus monkey compound at the Yerkes National Primate Research Center in Atlanta. Food is freely available, and the high-status females do not pride themselves on passing it up.

In fact, the dominant females ordinarily eat a little more than the subordinates. The lower status monkeys can get as much food as they want but seem to have less of a desire to eat, perhaps because of the higher level of stress hormones in their brain.

But suppose you tempted them with the equivalent of chocolate and potato chips and ice cream? Mark Wilson, a neuroscientist at Emory University, and a team tried that experiment at Yerkes by installing feeders with a constant supply of banana-flavored pellets.

Once these foods were available, the low-status monkeys promptly developed an appetite. They began eating significantly more calories than their social superiors. While the dominant monkeys dabbled in the sweet, fatty pellets just during the daytime, the subordinate monkeys kept scarfing them down after dark.

The experiment intrigues scientists studying human junk-food binges, which are hard to understand because there are so many confounding factors.

For the monkeys the situation seems simple. They get some sort of comfort that is particularly appealing to the subordinate monkeys. One possibility is that the fatty foods help block the monkeys’ stress responses.

Another possible explanation, the one favored by the Yerkes researchers, is that the snacks activated the reward pathways in the brain. They may have provided the same sort of dopamine reward as cocaine, which was studied in a previous experiment with monkeys by researchers at Wake Forest University.

“Essentially, eating high-calorie foods becomes a coping strategy to deal with daily life events for an individual in a difficult social situation,” Dr. Wilson said.

Debra A. Zellner, a psychologist at Montclair State University, tested both men and women by putting bowls of potato chips, M&Ms, peanuts and red grapes on a table as the participants in the study worked on solving anagrams.

The stress seemed to affect snacking in different ways for each sex. The women given solvable puzzles ate more grapes than M&Ms, while the women under stress preferred M&Ms.

Humans are not as lucky as monkeys in one way. “Female humans report that they eat high-calorie foods to make themselves feel better when stressed,” Dr. Zellner says, “but they actually don’t feel better after eating them. Instead, because they are restrained eaters, they feel guilt and actually feel worse. Female monkeys don’t have that cognitive baggage.”

Only the monkeys, it seems, find comfort in comfort foods.

—John Tierney, The New York Times, 5/20/08