Even more surprising was the finding that kids and elderly people both showed more of a bias than college students. On one hand, the young and the old were quite good at responding to desirable information: Everyone updated their beliefs similarly when they learned they were less likely to get cancer or have their credit card stolen than they had initially believed. But when they learned their chances were worse than expected, kids, teenagers and older adults seemed to ignore this information more than college students and middle-aged individuals.

The behavioral economist Andrew Oswald has found that from about the time we are teenagers, our sense of happiness starts to decline, hitting rock bottom in our mid-40s. (Middle-age crisis, anyone?) Then our sense of happiness miraculously starts to go up again rapidly as we grow older. This finding contradicts the common assumption that people in their 60s, 70s and 80s are less happy and satisfied than people in their 30s and 40s.

How can we explain this? The first thing that comes to mind is that these changes have something to do with raising kids in our 30s and 40s. Could it be that having children in the household has a negative influence on our happiness?

Oswald ruled out this possibility. He also controlled for people being born in better times, marital status, education, employment status, income: The age pattern persisted. Even more surprising, the pattern held strong even though Oswald did not control for physical health. In other words, older individuals are happier and more satisfied than middle-aged individuals even though the health of the former is generally worse.

Oswald tested half a million people in 72 countries, in both developing and developed nations. He observed the same pattern across all parts of the globe and across sexes. Happiness diminishes as we transition from childhood to adulthood and then starts rising as we grow wrinkles and acquire gray hair.

And it’s not only we humans who slump in the middle and feel sunnier toward the end. Just recently, Oswald and colleagues demonstrated that even chimpanzees and orangutans appear to experience a similar pattern of midlife malaise.