Experimenter demand effects

Abstract

A study's internal and external validity is threatened by experimenter demand effects. This threat is taken seriously by experimental economists, who have developed a number of best practices to suppress or eliminate the potential role of such effects. We outline these best practices and review the literature to show that they are followed in the vast majority of published work. This adherence to best practice likely contributes to the limited evidence of experimenter demand effects uncovered in the literature. Specifically, we are not aware of examples where demand effects have been shown to influence the qualitative inference from a study. While good design goes a long way towards reducing the potential for experimenter demand effects, a complementary option, presented in our final section, is to derive bounds on the effect.