Watson, L. M., Cosby, R., Lee-Parritz, D. E. 1993. Behavioral effects of enrichment devices on laboratory primates with stereotypic and self-directed behavior. American Journal of Primatology 31, 355-356 (Abstract).

Single-caged long-tailed macaques showed a decrease in self-directed behavior, especially self-biting, floating limb, hair pulling, and excessive licking, when treats were in the feeder. Paradoxically, both pacing and rocking increased when treats were in the feeder. A temporary reduction in some behavior pathology was noted, possibly due to replacing the stereotypic behaviors with activities directed toward the feeder.The ability of environmental enrichment devices to ameliorate stereotypic and self-aggressive behavior in laboratory primates is unclear.