New York - Chimpanzees in a midlife crisis? It sounds like a setup for a joke. "I believe no ape has ever purchased a sports car," said Andrew Oswald, an author of the study. But researchers report that captive chimps and orangutans do show the same low ebb in emotional well-being at midlife that some studies find in people. He and co-authors assembled data on 508 great apes from zoos and research centres in the US, Australia, Canada, Singapore and Japan. Social lifeCaretakers and other observers had filled out a four-item questionnaire to assess well-being in the apes. The questions asked such things as the degree to which each animal was in a positive or negative mood, how much pleasure it got from social situations, and how successful it was in achieving goals. Frans de Waal, an authority in primate behaviour at Emory University, cautioned that when people judge the happiness of apes, there may be a "human bias".Even happiness researcher Sonja Lyubomirsky of the University of California, Riverside, who thinks the U-shaped pattern in people is a statistical mirage, says she can't write off the ape result the same way. "I'm not really sure what it means," she said. "I am finding this very intriguing." Maybe it will spur more thinking about what's going on in both apes and humans, she said.