Psychology ETDs

Publication Date



The long term effects of early total social isolation in rhesus monkeys have been assumed to be static. This assumption, that young isolates' behavior does not differ from older, fully mature isolates' behavior, may not be valid in view of behavioral changes which have been shown to occur as monkeys age. The present research examined the effects of early, total social isolation in fully mature monkeys.

Two groups were formed and allowed to live together for 14 weeks in an indoor-outdoor facility. The first group was composed of 7 controls reared for the first 9 months of life with peer and maternal contact. The second group was composed of 6 isolates reared for the first 9 months of life in total social isolation. Both groups were composed of animals of similar age, ranging from 8-13 years of age. Each animal was observed daily for 3 minutes using a modified frequency scoring system with 11 categories. Periodically, each group was challenged with water depriva­tion, novel objects, monkey strangers, and apple incentivetests. During weeks 13-14 the dominant male was removed from the control group to assess his effect on the group's behavior.

The results indicated that fully mature social isolates exhibited very low levels of social behavior when compared to controls. Isolates exhibited no sexual behavior while controls had two live births as a function of their housing. Isolates were not found to be hyper­aggressive or overly fearful as had been reported earlier. Isolates displayed higher levels of nonsocial behavior (explore-self-manipulation) but did not differ otherwise.

Removal of the dominant male from the control group resulted in increased levels of social behavior within that group but did not significantly reduce aggression or domininance-submission behaviors. Results of the group's challenge tests indicated that isolates had a "tighter," more predictable dominance hierarchy than controls.

Fully mature, early total social isolates were found to be asocial and asexual. Isolates were not hyper­aggressive but were more likely to engage in self-directed behaviors than controls. The behavior of fully mature social isolates was found to be influenced by aging although many of the characteristic isolate behaviors remained.

Degree Name


Level of Degree


First Committee Member (Chair)

John Paul Gluck Jr.

Second Committee Member

Richard Jerome Harris

Third Committee Member

Francis S. Harnick

Fourth Committee Member

Karl Peter Koenig



Document Type


Included in

Psychology Commons