The 'jumping to conclusions' bias : a meta-analysis and empirical investigation of the effectiveness of implementation intentions

The reasoning of people with delusions is characterised by a 'Jumping to Conclusions' (JTC) bias. A meta-analysis of the empirical literature retrieved 54 effect sizes of the JTC bias from 30 papers. The magnitude of the effects implied that JTC is a robust phenomenon. The JTC effect was largest (d+ = .58) when measured by the amount of information requested to make a decision on probabilistic reasoning tasks. An analysis of methodological and theoretical factors which moderated JTC found that defining delusions by diagnosis of delusional disorder (d+ = .74) and employing black and white beads (d+ = .87), were associated with the largest effects. The degree of variance in effects indicates caution when interpreting the findings. An empirical study investigated JTC in eighty-five non-clinical participants divided into high and low paranoia groups. The study aimed to explore the impact of task variations on JTC and demonstrate the effectiveness of implementation intentions (if-then plans) in reducing hasty decision-making on probabilistic reasoning tasks. Given there was no evidence of JTC in the present sample, the findings do not support a role for JTC in the formation of delusions. There was a non-significant trend indicating that forming an implementation intention increased the amount of information requested. Task difficulty and bead colour also influenced the amount of information requested. Implementation intentions appeared most effective when the task was difficult and paranoia was high. Caution is required in drawing conclusions from these findings due to the limitations of the study.EThOS - Electronic Theses Online ServiceGBUnited Kingdo