A common factor underlying individual differences in confirmation bias.

When they are asked to test a given hypothesis, individuals tend to be biased towards confirming evidence. This phenomenon has been documented on different cognitive components: information search, weighing of evidence, and memory recall. However, the interpretation of these observations has been debated, and it remains unclear whether they truly reflect a confirmation bias (as opposed to e.g., a bias towards positive information). In the present study we aimed at evaluating whether these biases might be subtended by a common factor. We adapted three classic experimental paradigms on hypothesis testing (Wason selection task, 2-4-6 task, and interviewee task) and examined the relation between these biases using an individual differences approach. Participants (N = 200) completed a total of nine behavioral tasks, in which each component of confirmation bias was measured in each of the three experimental paradigms. Correlations and factor analyses within a multitrait-multimethod framework indicated greater convergence of bias scores within each component across paradigms, than within experimental paradigms. This suggests that a common factor underlies the different measurements of confirmation bias across experimental paradigms, at least to some extent. In these paradigms, thus, biases towards confirming evidence may truly reflect a confirmation bias.