A video-display approach to environmental enrichment for macaques (2003)

Kiyama, A., Taylor, A. J., McCary, J. L. et al.

Abstract

As part of an environmental enrichment program for rhesus monkeys at the University of Arizona, monkeys were given a bar press device in their home cages; bar presses were detected by a computer which was programmed to present video images to the animal contingent upon bar pressing. The purpose of this study was to provide the monkeys with a stimulating task that required bar manipulation and additionally provided the intrinsic reinforcement of novel visual stimuli. Two adult, individually caged male rhesus were subjects of this study. The present analysis established that for one of the monkeys (Dexter) the enrichment device was fully utilized for the time it was available. Dexter performed an average of 428 bar presses per hour, the videotape records showingtotal preoccupation with the task for the 1-hour testing periods. Dexter's viewing of the images became progressively longer throughout the testing session, providing further evidence that the task was absorbing for this monkey. Ambi, in contrast, appeared to engage in bar pressing for the opportunity to press the bar: 70 lever presses per houron average, consistent with previous studies showing that macaques appear to enjoy motor acts (Line et al. 1989).We infer that Ambi did not press the lever for the stimuli -- he pressed the lever but rarely viewed the video images that resulted from the pressing. Thus, while both monkeys found the lever and video-display enriching (as measured by the time and effort spent lever-pressing), they did so for different reasons.