The effect of incentivization on the conjunction fallacy in judgments: a meta-analysis

The conjunction fallacy is a classical judgment bias that was argued to be a robust cognitive illusion insensitive to the positive effect of incentivization. We conducted a meta-analysis of the literature (n = 3276) and found that although most studies did not report a significant effect of incentivization, the results across studies show a significant positive effect for incentivization, d = 0.19, with an odds ratio of 1.40 for answering correctly when incentivized. There was no moderating effect of payoff size despite the differences in incentive value between studies. Additionally, the effect was relatively smaller when examining absolute differences in the probability of correct judgment instead of odds ratios, suggesting that it may be partly driven by studies with low baseline performance. These findings join those of other judgment-bias studies to suggest a small but nevertheless robust debiasing effect of incentivization.