Another possibility is that people “might well anticipate substantial change, yet not know how they would change, and thus, just predict the status quo”
To give a specific example: If personality can be modeled over time as a martingale)—meaning that the expected future personality is always equal to the current personality—then it is quite appropriate for participants to provide their current personality as a prediction of their future personality, even if they think that the standard deviation of the martingale is large.
More generally, given the current personality c and random variable p following the distribution of predicted future personality, the predicted change in personality can be characterized by the expected absolute deviation
) or the expected squared deviation
%5E2)). However, study 1 in the paper measured the absolute expected deviation
%7C) instead, which is a poor measure. (This limitation of the study is understandable because collecting data on c and
) is relatively easy.)
The authors tried to circumvent this limitation in a replication of study 1 by asking each participant to directly predict change rather than inferring predicted change from c and
). P. 97 column 2:
Instead of being asked to report or predict their specific personality traits, these participants were simply asked to report how much they felt they had “changed as a person over the last 10 years” and how much they
thought they would “change as a person over the next 10 years.”
I think there is an interpretational issue here—we cannot be sure if the participants actually estimated something similar to the expected absolute deviation
). If the participants relied on imagining a future self, then this will again give the absolute expected deviation
%7C).
I’m surprised that the authors did not report whether any of the Big Five personality domains mediated this “end of history illusion”. That seems like an obvious thing to check. Maybe they’re saving that for a later paper.
“The single best way to make predictions about what you’re going to want in the future isn’t to imagine yourself in the future, … it’s to look at other people who are in the very future you’re imagining,” [Gilbert] says.
The distinction you highlight between the expected absolute deviation and the absolute expected deviation seems extremely important; Jordan Ellenberg says that the study is measuring one and calling it the other, and goes on to say (emphasis added)
Let me be clear: I don’t think the authors are trying to put one over. This is a mistake — a somewhat subtle mistake, but a bad mistake, and one which kills a big chunk of the paper. Science should not have accepted the article in its current form, and the authors should withdraw it, revise it, and resubmit it.
Thanks for the link. Ellenberg gives a great analogy to stock prices and points out something important: the study measured the absolute expected deviation
|) for the predictors, but measured the expected absolute deviation
) for the reporters.
This difference can explain the observed discrepancy between the two groups without invoking the “end of history illusion” because
%20%3E%20|c%20-%20\operatorname%20E(p)|).
This difference came about because obtaining an X+10-year-old’s report of current personality is equivalent to drawing a random sample from an X-year-old’s distribution of actual future personality, but the X-year-olds’ are providing point-estimates (of something like the mean) from their distributions of predicted future personality.
To give a specific example: If personality can be modeled over time as a martingale)—meaning that the expected future personality is always equal to the current personality—then it is quite appropriate for participants to provide their current personality as a prediction of their future personality, even if they think that the standard deviation of the martingale is large.
More generally, given the current personality c and random variable p following the distribution of predicted future personality, the predicted change in personality can be characterized by the expected absolute deviation
The authors tried to circumvent this limitation in a replication of study 1 by asking each participant to directly predict change rather than inferring predicted change from c and
I think there is an interpretational issue here—we cannot be sure if the participants actually estimated something similar to the expected absolute deviation
I’m surprised that the authors did not report whether any of the Big Five personality domains mediated this “end of history illusion”. That seems like an obvious thing to check. Maybe they’re saving that for a later paper.
In other words, take the outside view.
The distinction you highlight between the expected absolute deviation and the absolute expected deviation seems extremely important; Jordan Ellenberg says that the study is measuring one and calling it the other, and goes on to say (emphasis added)
Thanks for the link. Ellenberg gives a great analogy to stock prices and points out something important: the study measured the absolute expected deviation
This difference can explain the observed discrepancy between the two groups without invoking the “end of history illusion” because
This difference came about because obtaining an X+10-year-old’s report of current personality is equivalent to drawing a random sample from an X-year-old’s distribution of actual future personality, but the X-year-olds’ are providing point-estimates (of something like the mean) from their distributions of predicted future personality.