Think you'll be the same person in 10 years that you are today? Think again. Most people realize they've changed in the past, but few expect to change in the future, a new study finds.

Instead, while acknowledging that their tastes, values and even personality have varied over the past decade, people tend to insist the person they are today is the person they will be in 10 years — a belief belied by the evidence, said study researcher Daniel Gilbert, a psychologist at Harvard University.

"It's not that we don't realize change happens, because we all admit at every age that a lot of change has happened to us in the last 10 years," Gilbert told LiveScience. "All of us seem to have this sense that development is a process that has delivered us to this point and now we're done."

Permanent personality

In a new study published this week (Jan. 4) in the journal Science, Gilbert and his colleagues dub this mistaken belief the "end of history" illusion. No matter what age, Gilbert said, people act as if history shaped them and ended, leaving them in their final form. [7 Ways the Mind & Body Change With Age]

The illusion emerged when the researchers recruited participants online to fill out various personality, preference and value surveys as themselves 10 years prior and as themselves 10 years in the future. Over the series of studies, more than 19,000 people participated.

In each case, the researchers compared the look-ahead answers of 18-year-olds with the look-back answers of 28-year-olds, and so forth (comparing 19-year-olds with 29-year-olds, and 20-year-olds with 30-year-olds) all the way up to age 68. The older ages always reported changing in the past decade, but the younger ages did not expect to change nearly as much in the future as their elders' experiences suggested they would.

"When a 40-year-old looks backward, they say, 'I've changed a lot in terms of my personality, in terms of my values, in terms of my preferences,'" Gilbert said. "But when 30-year-olds look forward, they say, 'I don't expect to change a lot on any of those dimensions.'"

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To make sure the results weren't a consequence of people overestimating their past change rather than underestimating their future change, the researchers analyzed the actual personality change of 3,808 people who filled out personality questionnaires in 1995-96 and then again in 2004-05. Sure enough, the measures of actual change in this group were nearly identical to the reports of change among the current study participants. In other words, people are good at gauging how much they've changed in the past. It's the future that gives them trouble.

The "end of history" illusion may be driven by two factors, Gilbert said. One is that people find it comforting to believe that they know themselves and that the future is predictable. Thus, people are motivated to see the present as permanent.

The other is that it's simply harder to imagine the future than to remember the past. People may struggle to imagine how they might change and mistakenly conclude that since they can't figure it out, they won't change at all, Gilbert said.

Consequences of changing

This misjudgment can have real-world consequences, Gilbert said. For one thing, people make a number of life choices, from marriages to careers, assuming that decades from now they'll like the same people and activities they do today. The researchers even demonstrated some of these consequences by asking 170 people, ranging in age from 18 to 64, how much they'd pay today to see their favorite band perform in 10 years. They also asked how much the people would be willing to pay to see their favorite band of 10 years ago perform this week. [7 Personality Traits That Are Bad For You]

People were willing to shell out $130 to see their current favorite band in a decade. But they wanted to part with only $80 to see their former favorite band play now. The gap suggests people are overestimating how similar their future preferences will be to their current ones, Gilbert said.

Psychologists actually know quite a bit about how personality and values change over a lifetime, Gilbert added. For example, people tend to become less open to new experience over time but more conscientious, he said. And the older you are, the less you're likely to change in the future — though you'll still probably change more than you expect, this study suggests.

"If we know that our preferences are likely to be less stable than they feel, we can take great care when we make decisions. We can build in a margin for escape – so, for example, if I am going to buy a ticket to see a concert in 10 years, I ought to buy a refundable ticket," Gilbert said.

But before you write a 10-year opt-out clause into your wedding vows, take heed: Gilbert's other research has found that when people feel they have the ability to change their minds, they're less happy with the choices they've made. People who make irrevocable choices tend to be happier with them than those who can flip-flop later, Gilbert said.

"The best of all possible worlds would be a world in which you're allowed to change your mind but you don't know it," he said.

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