The survey also asked about “global well-being” by having each person rank overall life satisfaction on a 10-point scale, an assessment many people may make from time to time, if not in a strictly formalized way.

Finally, there were six yes-or-no questions: Did you experience the following feelings during a large part of the day yesterday: enjoyment, happiness, stress, worry, anger, sadness. The answers, the researchers say, reveal “hedonic well-being,” a person’s immediate experience of those psychological states, unencumbered by revised memories or subjective judgments that the query about general life satisfaction might have evoked.

The results, published online May 17 in the Proceedings of the National Academy of Sciences, were good news for old people, and for those who are getting old. On the global measure, people start out at age 18 feeling pretty good about themselves, and then, apparently, life begins to throw curve balls. They feel worse and worse until they hit 50. At that point, there is a sharp reversal, and people keep getting happier as they age. By the time they are 85, they are even more satisfied with themselves than they were at 18.

In measuring immediate well-being  yesterday’s emotional state  the researchers found that stress declines from age 22 onward, reaching its lowest point at 85. Worry stays fairly steady until 50, then sharply drops off. Anger decreases steadily from 18 on, and sadness rises to a peak at 50, declines to 73, then rises slightly again to 85. Enjoyment and happiness have similar curves: they both decrease gradually until we hit 50, rise steadily for the next 25 years, and then decline very slightly at the end, but they never again reach the low point of our early 50s.

Other experts were impressed with the work. Andrew J. Oswald, a professor of psychology at Warwick Business School in England, who has published several studies on human happiness, called the findings important and, in some ways, heartening. “It’s a very encouraging fact that we can expect to be happier in our early 80s than we were in our 20s,” he said. “And it’s not being driven predominantly by things that happen in life. It’s something very deep and quite human that seems to be driving this.”