Probability of minority inclusion is underestimated

Abstract

Perception of the probability of minority inclusion in the groups with which we interact is important to daily behaviours (e.g., teachers may consider the probability that a class of 30 students includes at least one gay/bisexual student). The present study showed that the participants surprisingly underestimated this probability even when the group size and the prevalence of the minority were given. Approximately 90% of the participants estimated lower than the mathematically normative probability. The underestimation was larger than in the case of the arithmetically isomorphic probability of the cumulative risk, suggesting a cognitive bias specific to the probability of inclusion. Some of the heuristics used for the estimations, such as the participants using an expected value, were relevant to the underestimation. This cognitive bias may mislead people into believing that minorities are irrelevant to them. It was also shown that the participants’ attitudes became more inclusive when they were informed of the normative probability of inclusion.