Editing Representativeness heuristic (section)

===Tom W.===
In a study done in 1973,{{sfn|Kahneman|Tversky|1973}} Kahneman and Tversky divided their participants into three groups:

*"Base-rate group", who were given the instructions: "Consider all the first-year graduate students in the U.S. today. Please write down your best guesses about the percentage of students who are now enrolled in the following nine fields of specialization." The nine fields given were business administration, computer science, engineering, humanities and education, law, library science, medicine, physical and life sciences, and social science and social work.{{sfn|Kahneman|Tversky|1973}}
*"Similarity group", who were given a personality sketch. "Tom W. is of high intelligence, although lacking in true creativity. He has a need for order and clarity, and for neat and tidy systems in which every detail finds its appropriate place. His writing is rather dull and mechanical, occasionally enlivened by somewhat corny puns and by flashes of imagination of the sci-fi type. He has a strong drive for competence. He seems to feel little sympathy for other people and does not enjoy interacting with others. Self-centered, he nonetheless has a deep moral sense." The participants in this group were asked to rank the nine areas listed in part 1 in terms of how similar Tom W. is to the prototypical graduate student of each area.{{sfn|Kahneman|Tversky|1973}}
*"Prediction group", who were given the personality sketch described in 2, but were also given the information "The preceding personality sketch of Tom W. was written during Tom's senior year in high school by a psychologist, on the basis of projective tests. Tom W. is currently a graduate student. Please rank the following nine fields of graduate specialization in order of the likelihood that Tom W. is now a graduate student in each of these fields."{{sfn|Kahneman|Tversky|1973}}

The judgments of likelihood were much closer for the judgments of similarity than for the estimated base rates. The findings supported the authors' predictions that people make predictions based on how representative something is (similar), rather than based on relative base rate information. For example, more than 95% of the participants said that Tom would be more likely to study computer science than education or humanities, when there were much higher base rate estimates for education and humanities than computer science.{{sfn|Kahneman|Tversky|1973}}