Laura Carstensen

If you reach 65, you've got a good chance of making it to 90.

So things have shifted very quickly in terms of length of life, but our expectations are old.

Absolutely.

I mean, today, 65-year-olds in my book are not old.

And in fact, a lot of the emails I got after our conversations

comprised messages of people telling me I'm not old.

I'm happy, but I'm not old.

Right.

That's a great question.

And so when these findings first appeared, people asked this question exactly.

Is it a selection effect?

Are these people who have always been happy?

Which is part of the motivation for a longitudinal study that my colleagues and I ran where we followed people over time.

And

We found that there was this change in people from being more negative when they were young within individual change to more positive when they were older.

So we don't think that a selection effect accounts for the full finding.

However, it is the case that happiness contributes to life expectancy.

That's a fairly modest contribution.

So both are true, but selection doesn't account for everything.

Well, the data suggests it's driven more by less sadness than an increase in happiness.