Economists and psychologists argue that individuals skew personal beliefs to accord with their own interests. To test for the presence of self-serving beliefs, we surveyed 1,200 members of the Mormon Church about tithing. A tithe is a voluntary contribution equal to 10 percent of income. Since respondents must decide privately what income items to tithe, we observe how the income definition depends on an individual’s religious and financial incentives. We find surprisingly little evidence that an individual’s financial situation influences beliefs about what counts as income for the tithe. However, ambiguity increases the role for self-serving biases. (JEL A12, D63)

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Our research on tithing practices does not imply that individuals will not protect their self-interest by professing to hold beliefs that benefit them. Rather, our research focuses on how self-interest influences beliefs at the subconscious level. We find that, when thinking about the tithe, Latter-Day Saints possess the ability to sort out their financial self-interest from a general standard of what is right or fair. While it is possible that our results do not generalize to other groups and issues, our survey nonetheless provides an interesting comparison to the literature that finds individuals are unable to filter out their own interest in a variety of other settings.