Base rate neglect and conservatism in probabilistic reasoning: Insights from eliciting full distributions

Abstract

Bayesian statistics offers a normative description for how a person should combine their original beliefs (i.e., their priors) in light of new evidence (i.e., the likelihood). Previous research suggests that people tend to under-weight both their prior (base rate neglect) and the likelihood (conservatism), although this varies by individual and situation. Yet this work generally elicits people’s knowledge as single point estimates (e.g., x has a 5% probability of occurring) rather than as a full distribution. Here we demonstrate the utility of eliciting and fitting full distributions when studying these questions. Across three experiments, we found substantial variation in the extent to which people showed base rate neglect and conservatism, which our method allowed us to measure for the first time simultaneously at the level of the individual. While most people tended to disregard the base rate, they did so less when the prior was made explicit. Although many individuals were conservative, there was no apparent systematic relationship between base rate neglect and conservatism within each individual. We suggest that this method shows great potential for studying human probabilistic reasoning.

Bayesian Advice Taking: Adaptive Strategy Selection in Sequential Advice Seeking

“…Note that the large performance variability of the choosing-self strategy for holistic distributional predictions is inherited from the judgment parameter. In Previous research suggests that the existence of certain weighting fallacies (i.e., base rate neglect, conservatism) varies between individuals and situations (Howe et al, 2022).…”

“…Specifically, in contrast to other experiments employing a sampling approach to advice taking (e.g., Hütter & Ache, 2016;Scheunemann et al, 2020), this experiment involved distributional measures of confidence regarding participants' initial and final judgments. Previous research suggests that the impact of weighting fallacies (i.e., base rate neglect, conservatism) varies not only between individuals but also between situations (Howe et al, 2022). Therefore, our aim is to generate insights mainly with respect to individual differences in participants' information aggregation strategies in judgment tasks that allow to sequentially sample external evidence.…”