Howell, S. M., Miteva, E., Fritz, J. et al. 1997. The provision of cage furnishings as environmental enrichment at the Primate Foundation of Arizona. The Newsletter 9(2), 1-5.

Results suggest a preference for horizontal furnishings above the enclosure floor. Adults infrequently used 'moving' furnishings (e.g., swinging ropes, hanging tubes, etc...) and seemed to prefer 'stable' horizontal furnishings (e.g., benches, logs) above the enclosure floor.