In the lifetime of a person, several lies have been told to him/her or by him/her. However, the reason why these lies have been told varies significantly across situations. Through a self-report study, this paper explores the motivations behind people’s altruistic lies and whether more selfish intentions are at the source of these lies. In addition, it attempts to see whether people lie about the reasons why they tell these altruistic lies. This was done through the use of an economic truth serum, known as the Bayesian Truth Serum (BTS), which induces people to tell the truth by financially rewarding them when they answer a survey truthfully. The survey contained two main questions: one which focused on the main motivation people had behind their altruistic lies and another which asked whether people had lied more than once in the past 24 hours. The 400 respondents gathered were divided into two conditions: one control condition and one subjected to the BTS. The goal of this research was to see whether being subjected to the BTS provided significantly different responses to the two main questions, compared to the control condition. In other words whether respondents not facing the BTS were dishonest. The results show that people not facing the BTS do not have significantly different responses than those facing the BTS. Therefore, no evidence is found indicating that people not facing the BTS were lying. Nevertheless, the BTS validates that in general people have more selfish motivations when telling altruistic lies and that the majority of people lie at most once in a day.

Additional Metadata
Keywords Bayesian Truth Serum, Lie detection, lies
Thesis Advisor A. Baillon
Persistent URL
Series Economics
A. Guilloux. (2018, November 29). Using the BTS to find the Truth behind the Untruth. Economics. Retrieved from