Use of base rates and case cue information in making likelihood estimates.

In five experiments, we investigated college students' use of base rate and case cue information in estimating likelihood. The participants reported that case cues were more important than base rates, except when the case cues were totally uninformative, and made more use of base rate information when the base rates were varied within subjects, rather than between subjects. Estimates were more Bayesian when base rate and case cue information was congruent, rather than contradictory. The nature of the "witness" in case cue information (animate or inanimate) did not affect the use of base rate and case cue information. Multiple trials with feedback led to more accurate estimates; however, this effect was not lasting. The results suggest that when base rate information is made salient by experience (multiple trials and within-subjects variation) or by other manipulations, base rate neglect is minimized.