Judgment under Uncertainty: Heuristics and Biases
Science, 1974 · paper · Psychology
Describes three heuristics people use to judge probabilities and predict values: representativeness, availability and adjustment from an anchor. Argues they are often useful but cause severe, systematic errors, and discusses the biases and their implications.
Checked: PDF from sites.stat.washington.edu, fetched 5 Oct 2026. Page numbers are those of that PDF.
0 findings
None that passed a second check.
4 minor (typos and the like; most checked by the judge only)
Wording "regression toward the mean, which was first documented by Galton more than 100 years ago": counted from 1974, Galton's usually cited work on regression (1877 and 1885-86) is 88 to 97 years earlier, not more than 100.
- p. 3 Misconceptions of regression, column 3
first documented by Galton more than 100 years ago.
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: the dates of Galton's work on regression (1877 sweet-pea lecture, 1885-86 papers on stature). The page prints the sentence as quoted (crop of PDF page 3) and the article gives no reference for Galton, so the dates cannot be checked from the files. If the authors had Hereditary Genius (1869) in mind, the phrase holds (105 years). A loose round figure at most; a query for the authors, not a certain error.
Second check: another model agreed
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Wording The first group "assessed either X10 or X90 for each problem", and the second group judged "the odds that each of the given values exceeded the true value", yet the unbiased answer is given as the single figure "9 : 1"; for the X10 items the odds as worded would be 1:9.
- p. 7 Anchoring in the assessment of subjective probability distributions, column 1
assessed either X10 or X90 for each prob-
- p. 7 Anchoring in the assessment of subjective probability distributions, column 1
They were asked to assess the odds that each of the given values exceeded the true value of the relevant quantity.
- p. 7 Anchoring in the assessment of subjective probability distributions, column 1
group should retrieve the odds specified to the first group, that is, 9 : 1.
- p. 6 column 3, definition of procedure (ii)
abilities that the true value of the Dow-Jones will exceed some specified values
Judge's note: Viewed crops of PDF pages 6 and 7. Page 6 defines X90 as the value with subjective probability .90 of being higher than the true value (9 to 1 odds), so X10 is higher than the true value with probability .10. Page 7 gives one figure, 9:1, for both kinds of item without saying the odds are expressed for the more likely side; that is evidently what is meant ("less extreme, that is, closer to 1 : 1"), so this is an unstated convention, not a wrong number. The second point, that procedure (ii) on page 6 is worded as the true value exceeding the specified value while the page 7 experiment is worded the other way, is real but the paper itself calls the forms formally equivalent. The first quote, not found in the text layer, is on the page image as "assessed either X10 or X90 for each prob-lem" with subscripts.
Second check: another model agreed
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Typo Missing full stop between two sentences in the urn example: "and found that 4 were red and 1 was white Another individual has drawn 20 balls".
- p. 2 Insensitivity to sample size, indented urn example, middle column
and 1 was white Another individual has
- p. 2 urn problem, right column
1 was white Another individual has drawn 20 balls
Judge's note: Viewed the crop of PDF page 2. There is no mark between "white" and "Another", only an ordinary word space, while the capital A starts a new sentence. Other full stops in the same indented paragraph ("another. One individual", "were white. Which") are printed clearly, so scan loss is unlikely, though it cannot be fully excluded for a scanned copy.
Second check: none (judge only)
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Typo A full stop is printed where a comma is needed: "After observing a long run of red on the roulette wheel. for example, most people erroneously believe".
- p. 2 Misconceptions of chance, gambler's fallacy sentence
After observing a long run of red on the roulette wheel. for example, most people erroneously believe
Judge's note: Viewed the crop of PDF page 2. The mark after "wheel" is a round dot on the baseline with no tail, followed by lower-case "for"; the comma after "example" on the next line and other commas nearby are intact. Caveat: this is a scan, and the same thing occurs on page 3 ("husbands and wives. or"), so a comma whose tail failed to print or scan cannot be ruled out. Settling it would need a clean copy of the original issue. Kept as an observation for that reason.
Second check: none (judge only)