Kessel, A. L., Brent, L. 1995. An activity cage for baboons, Part I. Contemporary Topics in Laboratory Animal Science 34(6), 74-79.

Single-housed baboons provided with a large enriched activity cage [during two days each month] display dramatic changes in behavior typically considered to represent positive psychological well-being. ....The home cages and the activity cage were located in the same room, and provided visual, olfactory, and auditory access to other baboons.