Dictator game experiments come in three flavors: plain vanilla with strictly dichotomous separation of dictator and recipient roles, an interactive alternative whereby every subject acts in both roles, and a variant thereof with role uncertainty. We add information regarding which of these three protocols was used to data from the leading meta-study by Engel (Exp Econ 14(4):583–610, 2011) and investigate how these variations matter. Our meta-regressions suggest that interactive protocols with role duality compared with standard protocols, in addition to being relevant as a control for other effects, render subjects’ giving less generous but more efficiency-oriented. Our results help organize existing findings in the field and indicate sources of confounds.