NEW YORK —
He and co-authors assembled data on 508 great apes from zoos and research centers in the U.S., Australia, Canada, Singapore and Japan. Caretakers 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. The raters were even asked how happy they would be if they were the animal for a week.
Sounds wacky? Oswald and his co-authors say research suggests it's a valid approach. And they found that the survey results produced that familiar U-shaped curve, adjusted to an ape's shorter lifespan.
"We find it for these creatures that don't have a mortgage and don't have to go to work and don't have marriage and all the other stuff," Oswald said. "It's as though the U shape is deep in the biology of humans" rather than a result of uniquely human experiences.
Yes, apes do have social lives, so "it could still be something human-like that we share with our social cousins," he said. "But our result does seem to push away the likelihood that it's dominantly something to do with human life."
Oswald said it's not clear what the evolutionary payoff might be from such discontent. Maybe it prods parents to be restless, "to help find new worlds for the next generation to breed," he said.
Frans de Waal, an authority in primate behavior at Emory University, cautioned that when people judge the happiness of apes, there may be a "human bias." But in an email he called the results "intuitively correct" and said the notion of biological influence over the human pattern is "an intriguing possibility."