Abstract: After reaching 4 months old, the grown-up albino rats weredivided, some housed in isolation and some in gregarious groups for 8weeks. Observations were made on their behavioral patterns of eating,drinking and sleeping. Thereafter all the rats were regrouped, putting 4strangers in one cage as a means of creating social stress to study itseffects on, the behavioral patterns of rats from both catagories.It wasfound that the behavioral changes in eating, drinking and sleepinginduced by social stress in isolated rats were more significant thanthose in gregarious rats,even though social isolation was carried outafter the rats were grown-up. Compared with gregarious rats, isolatedrats were characterized by stronger aggressive behavior. In comparisonwith the rats of which social isolation was carried out in early life(one month old), the behavioral changes during social stress in thegrown-up rats previously kept in social isolation were, however, lesssevere and they seemed to experience a shorter adaptation process.

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