Alexander Williams

The Bayesian ‘truth serum’ (BTS) is a scoring method that provides truthtelling incentives for respondents answering multiple-choice questions about intrinsically private matters (opinions, tastes, past behavior). The method requires respondents to supply not only personal answers but also percentage estimates of how other respondents will answer that same question. The scoring formula then assigns high scores to answers whose actual frequency is greater than their predicted frequency. It is a theorem that truthful answers maximize expected score, under fairly general conditions.