Objective
Standardized face-to-face interviews are widely used in low and middle-income countries to collect data for social science and health research. Such interviews can be long and tedious. In an attempt to improve the respondents' experience of interviews, we developed a concept of gamified interview format by including a game element. Gamification is reported to increase engagement in tasks, but results from rigorously developed research are equivocal, and a theory of gamification is still needed.

Materials & methods
We evaluated the proposed gamification with a randomized controlled trial based on self-determination theory, specifically on the basic psychological needs theory. In total, 1266 respondents were interviewed. Single and multiple mediation analyses were used to understand the effects of the gamified interview format.

Results
Our evaluation showed that the gamification we had developed did not improve the outcome, the experience of the interview reported by respondent. The effect of the gamified interview format depended on the ability of respondents: gamification can be counterproductive if it overburdens the respondents. However, the basic psychological needs theory explained the mechanisms of action of gamification well: feeling competent and related to others improved the reported experience of the interview.

Conclusion
We emphasize the need to develop context-specific gamification and invite researchers to conduct equivalently rigorous evaluations of gamification in future studies.