TED日本語 - ローラ・カーステンセン: 年をとるほど幸せになる

People are living longer and societies are getting grayer. You hear about it all the time. You read about it in your newspapers. You hear about it on your television sets. Sometimes I'm concerned that we hear about it so much that we've come to accept longer lives with a kind of a complacency, even ease. But make no mistake, longer lives can and, I believe, will improve quality of life at all ages.

Now to put this in perspective, let me just zoom out for a minute. More years were added to average life expectancy in the 20th century than all years added across all prior millennia of human evolution combined. In the blink of an eye, we nearly doubled the length of time that we're living. So if you ever feel like you don't have this aging thing quite pegged, don't kick yourself. It's brand new.

And because fertility rates fell across that very same period that life expectancy was going up, that pyramid that has always represented the distribution of age in the population, with many young ones at the bottom winnowed to a tiny peak of older people who make it and survive to old age is being reshaped into a rectangle.

And now, if you're the kind of person who can get chills from population statistics, these are the ones that should do it. Because what that means is that for the first time in the history of the species, the majority of babies born in the Developed World are having the opportunity to grow old.

How did this happen? Well we're no genetically hardier than our ancestors were 10,000 years ago. This increase in life expectancy is the remarkable product of culture -- the crucible that holds science and technology and wide-scale changes in behavior that improve health and well-being. Through cultural changes, our ancestors largely eliminated early death so that people can now live out their full lives.

Now there are problems associated with aging -- diseases, poverty, loss of social status. It's hardly time to rest on our laurels. But the more we learn about aging, the clearer it becomes that a sweeping downward course is grossly inaccurate. Aging brings some rather remarkable improvements -- increased knowledge, expertise -- and emotional aspects of life improve. That's right, older people are happy. They're happier than middle-aged people, and younger people certainly. Study after study is coming to the same conclusion.

The CDC recently conducted a survey where they asked respondents simply to tell them whether they experienced significant psychological distress in the previous week. And fewer older people answered affirmatively to that question than middle-aged people, and younger people as well. And a recent Gallup poll asked participants how much stress and worry and anger they had experienced the previous day. And stress, worry, anger all decrease with age.

Now social scientists call this the paradox of aging. After all, aging is not a piece of cake. So we've asked all sorts of questions to see if we could undo this finding. We've asked whether it may be that the current generations of older people are and always have been the greatest generations. That is that younger people today may not typically experience these improvements as they grow older. We've asked, well maybe older people are just trying to put a positive spin on an otherwise depressing existence. (Laughter) But the more we've tried to disavow this finding, the more evidence we find to support it.

Years ago, my colleagues and I embarked on a study where we followed the same group of people over a 10-year period. Originally the sample was aged 18 to 94. And we studied whether and how their emotional experiences changed as they grew older. Our participants would carry electronic pagers for a week at a time, and we'd page them throughout the day and evenings at random times. And every time we paged them we'd ask them to answer several questions -- On a one to seven scale, how happy are you right now? How sad are you right now? How frustrated are you right now? -- so that we could get a sense of the kinds of emotions and feelings they were having in their day-to-day lives.

And using this intense study of individuals, we find that it's not one particular generation that's doing better than the others, but the same individuals over time come to report relatively greater positive experience. Now you see this slight downturn at very advanced ages. And there is a slight downturn. But at no point does it return to the levels we see in early adulthood.

Now it's really too simplistic to say that older people are "happy." In our study, they are more positive, but they're also more likely than younger people to experience mixed emotions -- sadness at the same time you experience happiness; you know, that tear in the eye when you're smiling at a friend. And other research has shown that older people seem to engage with sadness more comfortably. They're more accepting of sadness than younger people are. And we suspect that this may help to explain why older people are better than younger people at solving hotly-charged emotional conflicts and debates. Older people can view injustice with compassion, but not despair.

And all things being equal, older people direct their cognitive resources, like attention and memory, to positive information more than negative. If we show older, middle-aged, younger people images, like the ones you see on the screen, and we later ask them to recall all the images that they can, older people, but not younger people, remember more positive images than negative images. We've asked older and younger people to view faces in laboratory studies, some frowning, some smiling. Older people look toward the smiling faces and away from the frowning, angry faces. In day-to-day life, this translates into greater enjoyment and satisfaction.

But as social scientists, we continue to ask about possible alternatives. We've said, well maybe older people report more positive emotions because they're cognitively impaired. (Laughter) We've said, could it be that positive emotions are simply easier to process than negative emotions, and so you switch to the positive emotions? Maybe our neural centers in our brain are degraded such that we're unable to process negative emotions anymore. But that's not the case. The most mentally sharp older adults are the ones who show this positivity effect the most. And under conditions where it really matters, older people do process the negative information just as well as the positive information.

So how can this be? Well in our research, we've found that these changes are grounded fundamentally in the uniquely human ability to monitor time -- not just clock time and calendar time, but lifetime. And if there's a paradox of aging, it's that recognizing that we won't live forever changes our perspective on life in positive ways. When time horizons are long and nebulous, as they typically are in youth, people are constantly preparing, trying to soak up all the information they possibly can, taking risks, exploring. We might spend time with people we don't even like because it's somehow interesting. We might learn something unexpected.

(Laughter) We go on blind dates. (Laughter) You know, after all, if it doesn't work out, there's always tomorrow. People over 50 don't go on blind dates. (Laughter)

As we age, our time horizons grow shorter and our goals change. When we recognize that we don't have all the time in the world, we see our priorities most clearly. We take less notice of trivial matters. We savor life. We're more appreciative, more open to reconciliation. We invest in more emotionally important parts of life, and life gets better, so we're happier day-to-day. But that same shift in perspective leads us to have less tolerance than ever for injustice.

By 2015, there will be more people in the United States over the age of 60 than under 15. What will happen to societies that are top-heavy with older people? The numbers won't determine the outcome. Culture will. If we invest in science and technology and find solutions for the real problems that older people face and we capitalize on the very real strengths of older people, then added years of life can dramatically improve quality of life at all ages. Societies with millions of talented, emotionally stable citizens who are healthier and better educated than any generations before them, armed with knowledge about the practical matters of life and motivated to solve the big issues can be better societies than we have ever known.

My father, who is 92, likes to say, "Let's stop talking only about how to save the old folks and start talking about how to get them to save us all."

Thank you.

(Applause)