Taking A Closer Look At The Bayesian Truth Serum: A Registered Report (Stage 2 Registered Report)

Over the past decade, psychology and its cognate disciplines have undergone substantial scientific reform, ranging from advances in statistical methodology to significant changes in academic norms. One aspect of experimental design that has received comparatively little attention is incentivisation, i.e. the way that participants are rewarded and incentivised monetarily for their participation in experiments and surveys. While incentive-compatible designs are the norm in disciplines like economics, the majority of studies in psychology and experimental philosophy are constructed such that individuals’ incentives to maximise their payoffs in many cases stand opposed to their incentives to state their true preferences honestly. This is in part because the subject matter is often self-report data about subjective topics and the sample is drawn from online platforms like Prolific or MTurk where many participants are out to make a quick buck. One mechanism that allows for the introduction of an incentive-compatible design in such circumstances is the Bayesian Truth Serum (BTS; Prelec, 2004), which rewards participants based on how surprisingly common their answers are. Recently, Schoenegger (2021) applied this mechanism in the context of Likert-scale self-reports, finding that the introduction of this mechanism significantly altered response behaviour. In this registered report, we further investigate this mechanism by (i) attempting to directly replicate the previous result and (ii) analysing if the Bayesian Truth Serum’s effect is distinct from the effects of its constituent parts (increase in expected earnings and addition of prediction tasks). We fail to replicate the effect of the BTS on response behaviour and are as such unable to recommend wide adoption of the BTS on the basis of these data. Further, we provide weak evidence that the prediction task itself influences response distributions and that this task’s effect is distinct from an increase in expected earnings, suggesting that the BTS’s effects may ameliorate distinct effects of its constituent parts.