Abstract

The effect of rearing in isolation on later emotionality and social behavior was studied using A strain male mice (Mus Musclus). Twenty-four mice were separated from own litters on the 21st day of life and reared in isolation for 70 days before they were tested for emotionality and social behavior. Another group of 24 mice were separated on the 21st day of life and henceforward reared in pairs before they were tested on the 91st day of life. The mice were observed in two situations, while they were in the observation cage in which they were carried to the open-field test apparatus from home cages and while they were released in the open· field test apparatus. In the brief duration in which the m ice were placed in the observation cage, more of the isolation-reared mice responded with tale-rattling and fewer of them showed running away response than the control group when prodded with a rod, and a greater number of the former animals showed defecation response while being held in the cage than the other group. The isolation reared mice also showed fewer escape response, and more biting response to being picked up by hand. In the open-field situation, the isolation-reared group tended to roam more freely than the group-reard group, but the two did not differ from each other in its approach response to another mouse which was kept in a corner of the test apparatus as a possible instigating stimulus of affiliation response from the subjects. The results generally agree with the findings of other studies that being reared in isolation from other animals early in life heighten emotionality in mature animal. But the fact that the isolated mice showed less tendency to escape from the threatening stimulus and a greater tendency to locomote freely in a novel situation seems to imply that in spite of heightened emotionality, in the case of mice, at least fear is somehow inadequately developed. Lack of fear possibly explains why the isolation-reared mice did not show greater affiliative response despite their early social deprivation experience.