Watson, L. M. 1992. Effect of an enrichment device on stereotypic and self-aggressive behaviors in singly-caged macaques: A pilot study. Laboratory Primate Newsletter 31(3), 8-10.

The [single-housed] macaques in this study 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.