"Coping with Crowding" by Frans B. M. de Waal, Filippo Aureli, and Peter G. Judge, in Scientific American (May 2000), 415 Madison Ave., New York, N.Y. 10017-1111.
Ever since a psychologist in the 1960s packed a bunch of rats into a room and observed the gruesome results, the idea that overcrowding promotes increased aggression and even violence in humans has become widespread. In recent decades, however, scientists have revised their view. People, after all, somehow navigate peacefully through crowded situations every day, jamming themselves into trains and elevators without ordinarily resorting to ratlike savagery. Despite their irritation and stress, people adjust and stay calm.
But why? Is it human intelligence or cultrue that prompts people to behave in this civilized fashion? No, say de Waal, a psychologist who directs the Living Links Center at the Yerkes Regional Primate Research Center in Atlanta, and his co-authors. Remaining cool in overcrowded situations is part of humans' evolutionary heritage.
Studying 122 rhesus monkeys at the Yerkes center and two other locations, the authors observed that overcrowded adult males became more friendly and no more aggressive, while females did get more aggressive but also made a "concerted effort" to improve their usually antagonistic relationships with non-kin.
Even more relevant was the behavior of 100 chimpanzees--the closest human relatives--studied at the Yerkes center. Chimps "are known for deceptive behavior," de Waal and his colleagues note, and in this case, put into cramped quarters, they seemed to hold their emotions in check. In contrast to the female rhesus monkeys, the chimps showed no increase in aggressive behavior. "We found that chimpanzees in the most crowded situations had a three times lower tendency to react" to neighboring animals' cries--which usually provoke hooting and charging displays--than chimps with more space did, the authors say. "Chimpanzees may be smart enough to suppress responses to external stimuli if those tend to get them into trouble."
Chimps actually became less aggressive when they were put into very crowded quarters for a brief time--which is "a daily experience in human society," de Waal and his colleagues note. On a crowded elevator, people tend to limit body movement, avoid eye contact, and refrain from talking loudly. It's not simply politeness, the authors suggest. It's a way that we "and other primates handle the risks of temporary closeness."