When I try to estimate the same thing several times, without remembering my earlier estimates, I tend to get different results. I strongly suspect this is universal, though I haven’t seen research on that question.
There is research by Val & Pashler (2008) showing a within-person wisdom of crowds effect. They asked each person a trivia question, and then asked the same question to the same person again two weeks later, and found that averaging those two answers provided 1⁄3 the accuracy benefit that you get from asking the question to two different people. Wisdom of crowds works because each person’s estimate is (the true value) + (systematic bias in the population) + (random person-specific noise), and the random person-specific noise cancels out when you average together more people. This result suggests that random person-specific noise actually breaks down into two parts: 2⁄3 is noise that depends stably on the person, and 1⁄3 of the noise varies within a person over time (although the exact proportions will presumably depend on the particular question and person).
There is research by Val & Pashler (2008) showing a within-person wisdom of crowds effect. They asked each person a trivia question, and then asked the same question to the same person again two weeks later, and found that averaging those two answers provided 1⁄3 the accuracy benefit that you get from asking the question to two different people. Wisdom of crowds works because each person’s estimate is (the true value) + (systematic bias in the population) + (random person-specific noise), and the random person-specific noise cancels out when you average together more people. This result suggests that random person-specific noise actually breaks down into two parts: 2⁄3 is noise that depends stably on the person, and 1⁄3 of the noise varies within a person over time (although the exact proportions will presumably depend on the particular question and person).