Conversational conventions, order of information acquisition, and the effect of base rates and individuating information on social judgments.

Numerous studies have shown that people underuse base-rate information in making social judgments and rely instead almost exclusively on individuating information. Seven studies reported here demonstrate that this occurred partly because most past studies gave subjects hase-rate information before giving them individuating information. A recency effect in the use of base-rate and individuating information is demonstrated using a set of reasoning problems of varying character. The recency effect is shown to be the result of subjects' inferences (based on conversational conventions) that the experimenter believes that subjects should rely most on the piece of information presented last. Additional evidence discredits the hypothesis that the recency effect is due to heightened availability of more recently acquired information in memory. One of the most engaging topics of research in social cognition has been the impact of base-rate information on social judgments. Numerous empirical studies have compared the impact of base-rate information with the impact of individuating information about a person on assessments of the person's category membership or likely future behavior. Although early research suggested that individuating information overwhelms base-rate information (e.g., Kahneman & Tversky, 1973; Nisbett & Borgida, 1975), later studies revealed that base-rate information can have substantial impact when the base rate is derived from a representative sample (Wells & Harvey, 1977), when the individuating information lacks credibility (Schwarz, Strack, Hilton, & Naderer, in press), when the base rate has strong causal implications (Ajzen, 1977), when people bring a scientific orientation to a problem (Zukier & Pepitone, 1984), or when inferential rules suggesting the use of base rates have been activated (Ginossar & Trope, 1987). Our focus in this article is on another factor that may regulate the impact of base-rate information: the order in which the base rate and individuating information is acquired by a judge. A majority of the studies that have documented underuse of base rates in social prediction tasks presented subjects with the baseSome of the research reported here constituted a portion of a master's thesis submitted by Fan Li to Ohio State University. Some of the studies reported here were presented at the 1988 annual meeting of the Midwestern Psychological Association, Chicago. This research was supported, in part, by NSERC Grant 87-1715 to Darrin R. Lehman. We wish to express our thanks to Ray Corteen, Eric Eich, Geoff Fong, Michael Geis, Rich Jagacinski, Tom Ostrom, and especially Denis Hilton for helpful comments. We also thank Jim Ashenhurst, who collaborated with us in conducting Study 2, and Tanya Gabille, who collaborated with us in conducting Study 6. Correspondence concerning this article should be addressed to Jon