Conformity in nonhuman primates: fad or fact?

Majority influences have long been a subject of great interest for social psychologists and, more recently, for researchers investigating social influences in nonhuman primates. Although this empirical endeavor has culminated in the conclusion that some ape and monkey species show “conformist” tendencies, the current approach seems to suffer from two fundamental limitations: (a) majority influences have not been operationalized in accord with any of the existing definitions, thereby compromising the validity of cross-species comparisons, and (b) the results have not been systematically scrutinized in light of alternative explanations. In this review, we aim to address these limitations theoretically. First, we will demonstrate how the experimental designs used in nonhuman primate studies cannot test for conformity unambiguously and address alternative explanations and potential confounds for the presented results in the form of primacy effects, frequency exposure, and perception ambiguity. Second, we will show how majority influences have been defined differently across disciplines and, therefore, propose a set of definitions in order to streamline majority influence research, where conformist transmission and conformity will be put forth as operationalizations of the overarching denominator majority influences. Finally, we conclude with suggestions to foster the study of majority influences by clarifying the empirical scope of each proposed definition, exploring compatible research designs and highlighting how majority influences are inherently contingent on situational trade-offs.