Erwin, J. , Deni, R. 1979. Strangers in a strange land: Abnormal behavior or abnormal environments? In: Captivity and Behavior. Erwin, J., Maple, T., Mitchell, G. (eds), 1-28. Van Nostrand Reinhold, New York, NY.

It is the purpose of this chapter to review some of the information on abnormal behavior of primates and the environmental factors associated with them. ... Virtually all captive-reared macaques confined in small cages early in life express this behavioral pattern [pacing]. ... A major problem among captive primates is apathy and depression.