Reviews current knowledge about primate displacement activities (DAs) by pointing to their potential value as a behavioral indicator of emotional states associated with social interactions. DAs tend to occur in situations of psychosocial stress, and their frequency of occurrence is affected by anxiogenic and anxiolytic drugs. It is argued that findings emerging from studies using DAs as behavioral indicators are likely to improve our understanding of the causal mechanisms and functional consequences of DAs. In addition, information on the emotional reactiveness of animals to social and environmental stimuli may shed light on how certain behavioral profiles are determined as well as on how predispositions to pathologies may arise. Methodological problems associated with such a use are discussed. The hypothesis that DAs may also have a communicative function in nonhuman primates is not supported by available data. (PsycINFO Database Record (c) 2016 APA, all rights reserved)