Would you like to live forever? Probably not.

According to a recent survey by the Pew Research Center, most Americans don’t want to stick around much longer than current life expectancy. Sixty percent don’t want to live past 90. Thirty percent don’t want to live past 80. People who make lots of money don’t want longer lives any more than the rest of us do. Nor do people who think there’s no afterlife.

What’s driving our misgivings? Much of it is uncertainty about what kind of lives we’d be living. Would medical progress keep us feeling young? Or would it only stretch out our declining years?

The survey of more than 2,000 U.S. adults packs several surprises. First, Americans are far more optimistic than is justified by current medicine or technology. By the year 2050 – just 37 years from now – 25 percent of the respondents think it’s at least probable that “the average person in the U.S. will live to be at least 120.” Sixty-nine percent think “there will be a cure for most forms of cancer.” Seventy-one percent think “there will be artificial arms and legs that perform better than natural ones.” Scientifically, there’s no reason to expect any of these achievements in that time frame.

Despite this optimism, Americans are less gung-ho about life extension than you’d imagine. A slight majority – 51 percent – say that “if new medical treatments slow the aging process and allow the average person to live decades longer, to at least 120 years old,” this would be “a bad thing for society.” Sixty-eight percent think that “most people would want these medical treatments,” but 56 percent, when asked whether “you, personally, would want” such treatments, say they wouldn’t. The prevailing view seems to be that everybody else wants to live forever, but not me.

Third, believing that death is final doesn’t make you more eager to postpone it. By a margin of 16 percentage points – 55 to 39 percent – people who believe in an afterlife say they wouldn’t want treatments to extend their lives to 120. People who don’t believe in an afterlife are more likely to say they wouldn’t want such treatments: 59 to 37 percent, a margin of 22 points.

Why so much resistance? One likely reason is dread about the nature of extended life. Pew’s survey explicitly postulated treatments that “slow the aging process.” But when you’re being asked about living to 120 years or beyond, it’s hard not to picture spending much of that time feeling withered, afflicted and debilitated. Although the survey didn’t ask about this assumption directly, several findings are consistent with it. For instance:

1. The more you associate medical treatment with higher quality of life, the more you favor life extension. Respondents who think “medical treatments these days are worth the costs because they allow people to live longer and better quality lives” are evenly divided on the idea of extending life to 120 years. But respondents who say “medical treatments these days often create as many problems as they solve” are against life extension by a ratio of nearly 2-1.

2. The more you associate longevity with productivity, the more you favor life extension.

3. The more you see extended life as a resource burden, the more you oppose it. By a ratio of nearly 2-1, respondents who think that “longer life expectancies would strain our natural resources” say that living to 120 would be bad for society. Respondents who reject the strained-resources claim draw the opposite conclusion: Fifty-nine percent say extended life would be socially beneficial.

4. The more you see old folks as a problem, the more you oppose life extension. Respondents who think having “more elderly people” is good for society are evenly split on extending life to 120 years. Respondents who think having more elderly people is bad solidly oppose this increase in longevity: Seventy-one percent say it would be bad for society.

5. The older you are, the less likely you are to favor life extension. Respondents ages 18 to 29 are closely divided: Forty-eight percent say that living to 120 would be good for society. In the next bracket, ages 30 to 49, support slips just a tad: Forty-six percent say living the extra decades would be good. At ages 50 to 64, support drops to 37 percent. At ages 65 and older, support drops to 31 percent.

6. People don’t want to live past the age at which severe diseases and disabilities are expected. When respondents are asked how long they’d like to live, fewer than 10 percent choose 100 or older. Twenty percent want to live into their 90s. Thirty-two percent want to live into their 80s. Thirty percent don’t want to make it past 80. Why do most people want to die before they reach 90? Probably because being 90 is awful. But that’s true only because of the current rate of physical decline.

There will always be folks who think it’s unnatural to live longer than what’s normal today. But what’s normal has already changed. Sixty-three percent of the Pew respondents, when asked whether life-prolonging medical advances “are bad because they interfere with the natural cycle of life,” reject this view, concluding instead that these advances “are generally good because they allow people to live longer.” Yet among this pro-longevity majority, 51 percent say that treatments extending life to 120 years “would be fundamentally unnatural.”

That’s blatant equivocation. How long can it be sustained? Why would these people, who already accept a 75 percent rise in life expectancy in the last century, balk at another 50 percent increase?

They won’t, of course. They’ll be long dead, leaving the new normal to their descendants. I think.