Photo D.2. The Macaque threatened and on the lookout.
Photo D.3. Preparation for experiments
Photo D.4. The experiments.
Photo D.5. Recording experiments and stimulation by food
Photo D.6. The monkey is stimulated by swinging
Photo D.7. Performance with drawer door
Photo D.8. Performances with hooks
Photo D.9. Performances with hooks, sliding bolts and latches
Photo D.10. Performances with sliding bolts