Delusion‐proneness or miscomprehension? A re‐examination of the jumping‐to‐conclusions bias

Previous research has consistently shown that individuals with delusions typically exhibit a jumping‐to‐conclusions (JTC) bias when administrated the probabilistic reasoning ‘beads task’ (i.e., decisions made on limited evidence and/or decisions over‐adjusted in light of disconfirming evidence). However, recent work in this area has indicated that a lack of comprehension of the task may be confounding this finding. The purpose of the present study was to evaluate the influence of task administration, delusion‐proneness, and miscomprehension on the elucidation of the JTC bias. A total of 92 undergraduate university students were divided into one of two task conditions (i.e., non‐computerised and computerised) and were further identified as either delusion‐prone or non‐delusion‐prone and as comprehending or non‐comprehending the task. Overall, 25% of the sample demonstrated a JTC bias, and just over half made illogical responses consistent with a failure to comprehend the task. Qualitative evidence of comprehension revealed that these ‘illogical responses’ were being driven by a misunderstanding of task instructions. The way the task was administrated and levels of delusion‐proneness did not significantly influence JTC. However, miscomprehending participants were significantly more likely to exhibit the bias than those who did comprehend. These results suggest that miscomprehension rather than delusion‐proneness may be driving the JTC bias, and that future research should include measures of miscomprehension.