National Geographic - New research says it's not just humans who go through midlife crises: Chimps and orangutans also experience a dip in happiness around the middle of their lives.
"There may be different things going on at the surface, but underneath it all, there's something common in all three species that's leading to this," said study leader Alexander Weiss, a primate psychologist at the University of Edinburgh in Scotland.
The study team asked longtime caretakers of more than 500 chimpanzees and orangutans at zoos in five countries to fill out a questionnaire about the well-being of each animal they work with, including overall mood, how much the animals seemed to enjoy social interactions, and how successful they were in achieving goals (such as obtaining a desired item or spot within their enclosure).
The survey even asked the humans to imagine themselves as the animal and rate how happy they'd be.
When Weiss's team plotted the results on a graph, they saw a familiar curve, bottoming out in the middle of the animals' lives and rising again in old age. It's the same U-shape that has shown up in several studies about age and happiness in people.