Bloomsmith, M. A., Alford, P. L., Maple, T. L. 1988. Successful feeding enrichment for captive chimpanzees. American Journal of Primatology 16, 155-164.

Four feeding techniques were simultaneously implemented: Corn on the cob/celery/artichokes, biscuits at libitum, sunflower seeds and peanuts spread in the grass, and puzzles filled with treats. Agonistic, abnormal, and grooming behaviors were significantly reduced.