Are People Programmed to Commit Fallacies? Further Thoughts about the Interpretation of Experimental Data on Probability Judgment

During the last decade or so a characteristic method of interpreting experimental data has been followed by most researchers in their investigations into how statistically untutored subjects actually judge probabilities. For the most part the investigator tacitly assumes that the problem-task set to his or her subjects is correctly soluble only in terms of some academically well-regarded conception of probabilities that he or she has in mind. The investigator therefore evaluates the subjects’ performance for correctness or incorrectness by a technique of assessment or estimation that is appropriate to this mode of conception. If some subjects’ responses seem, when thus evaluated, to be incorrect, their error may be put down by the investigator-in terms of the computational metaphor-either to a standing fault in the programming of ordinary people (in that they are not programmed to apply appropriate valid principles to the task in question or are programmed to apply inappropriate or invalid ones) or to a temporary malfunction in the running of a valid programme.