M. Barhillel et E. Neter, HOW ALIKE IS IT VERSUS HOW LIKELY IS IT - A DISJUNCTION FALLACY IN PROBABILITY JUDGMENTS, Journal of personality and social psychology, 65(6), 1993, pp. 1119-1131
One event cannot be more probable than another that includes it. Judgi
ng P(A & B) to be higher than P(A) has been called the conjunction fal
lacy. This study examined a disjunction fallacy. Ss received brief cas
e descriptions and ordered 7 categories according to 1 of 4 criteria:
(a) probability of membership, (b) willingness to bet on membership, (
c) inclination to predict membership, and (d) suitability for membersh
ip. The list included nested pairs of categories (e.g., Brazil-South A
merica). Ranking a category more probable than its superordinate, or b
etting on it rather than its superordinate, is fallacious. Prediction,
however, may be guided by maximizing informativeness, and suitability
need conform to no formal rule. Hence, for these 2 criteria, such a r
anking pattern is not fallacious. Yet ranking of categories higher tha
n their superordinates was equally common on all 4 criteria. The resul
ts support representativeness against alternative interpretations.