Developmental change in the use of base-rates and individuating information.

Adults tend to make biased inferences when they are given base-rates (i.e., prior probabilities) that conflict with individuating information (i.e., a personality description), relying heavily on individuating information. Recent work has shown that six-year-olds do the same, whereas four-year-olds rely more on prior probabilities. In the present article, we revisit the argument that producing responses that align closely with base-rates should necessarily be seen as normative. We instead posit that rational inferences should be sensitive to all relevant information and should depend on its strength. In three experiments, we explored four-year-olds', six-year-olds' (N = 200), and adults' (N = 196) information use by manipulating the strength of individuating and base-rate information. Across base-rate manipulations, adults showed a bias for individuating information regardless of its strength. In contrast, six-year-olds appeared to use each type of information flexibly, depending on which was more informative. Four-year-olds' performance was less clear: Although they relied on base-rates when they were informative, they struggled to use the individuating information in their inferences and did not appreciate the manipulation of the strength of individuating information. Thus, six-year-olds appear to more flexibly use multiple sources of information than both younger children and adults, suggesting a period in development where children are able to weigh information before they are too biased toward individuating information. (PsycInfo Database Record (c) 2021 APA, all rights reserved).