Leland, S. P., West, A. M., Pippin, Z. L. et al. 2008. Effects of familiarity and novelty on rates of environmental enrichment object manipulation by laboratory rhesus macaques (Macaca mulatta). American Journal of Primatology 70(S1), 30. (31st Meeting of the American Society of Primatologists Scientific Program, Abstract #29)

Manipulable objects are often provided to laboratory macaques as environmental enrichment, but exposure to objects is widely believed to result in rapid habituation. Consequently, much effort is made to ensure enrichment objects are novel. Here we report experimental comparisons of contact manipulation rates of novel and familiar commercial pet toys by adult rhesus macaques. Thirty individually housed macaques were studied in a laboratory with constant exposure to multiple enrichment toys. Three patterns were studied over a three-week period. All individuals in the Familiar-Control Group (n=10) had uninterrupted access to four toys. Each individual in the Familiar-Reintroduced Group (n=10) had access to four toys in Week One. One toy was absent during Week Two, but it was reintroduced at Week Three. Subjects in the Novelty Group (n=10) were treated like the Familiar-Reintroduced Group, except that an unfamiliar toy was introduced at Week Three instead of the familiar toy. Individuals were assigned to these comparison groups balancing age, sex, and baseline manipulation patterns observed during Week One. Each individual was observed during seven three-minute intervals/week, totaling sixty-three minutes/subject. The only significant effect found in this study was that the manipulation rate of the novel toy received by the Novelty Group was significantly lower [Wilcoxon Signed Rank Test, α=0.05] than for any familiar object. This result suggests that manipulation rates may be higher for familiar objects because their properties are known.