Today Ed Yong has a post on Not Exactly Rocket Science that is about updating - actually, the most extreme case in updating, where a person gets to choose between relying completely on their own judgement, or completely on the judgement of others. He describes 2 experiments by Daniel Gilbert of Harvard in which subjects are given information about experience X, and asked to predict how they would feel (on a linear scale) on experiencing X; they then experience X and rate what they felt on that linear scale.
In both cases, the correlation between post-experience judgements of different subjects is much higher than the correlation between the prediction and the post-experience judgement of each subject. This isn't surprising - the experiments are designed so that the experience provides much more information than the given pre-experience information does.
What might be surprising is that the subjects believe the opposite: that they can predict their response from information better than from the responses of others.
Whether these experiments are interesting depends on how the subjects were asked the question. If they were asked, before being given information or being told what that information would be, whether they could predict their response to an experience better by making their own judgement based on information, or from the responses of others, then the result is not interesting. The subjects in that case did not know that they would be given only a trivial amount of information relative to those who had the experience.
The result is only interesting if the subjects were given the information first, and then asked whether they could predict their response better from that information than from someone else's experience. Yong's post doesn't say which of these things happened, and doesn't cite the original article, so I can't look it up. Does anyone know?
I've heard studies like this cited as strong evidence that we should update more; but never heard that critical detail given for any such studies. Are there any studies which actually show what this study purports to show?
EDIT: Robin posted the citation. The original paper does not contain the crucial information. Details in my response to Robin.
EDIT: The original paper DOES contain the crucial info for the first experiment. I missed it the first time. It says:
.. a woman was escorted to the speed-dating room and left to have a 5-min private conversation with the man. Next, the experimenter escorted the woman to another room where she reported how much she had enjoyed the speed date by marking a 100-mm continuous “enjoyment scale” whose end points were marked not at all and very much. This report is hereinafter referred to as her affective report.
Next, a second woman was given one of two kinds of information: simulation information (which consisted of the man’s personal profile and photograph) or surrogation information (which consisted of the affective report provided by the first woman). The second woman was then asked to predict (on the enjoyment scale) how much she would enjoy her speed date with the man. This prediction is hereinafter referred to as her affective forecast.
After making her prediction, the second woman was shown the kind of information (simulation or surrogation) that she had not already received. We did this to ensure that each woman had the same information about theman before the actual speed date. The only difference between the two conditions, then, was whether the second woman had surrogation information or simulation information when she made her forecast.
Next, the second woman was escorted to the dating room, had a speed date, and then reported how much she enjoyed it (on the enjoyment scale). This report is hereinafter referred to as her affective report. The second woman also reported whether she believed that simulation information or surrogation information would have allowed her to make the more accurate prediction about the speed date she had and about a speed date that she might have in the future.