Effect of neonatal stunting on development of rats: large litter rearing

As nurslings, rat pups reared in large litters showed reduced frequencies of returns to their nest from other parts of the home cage and reached maximum levels of nest returns at older ages than control animals from small litters. These differences were not due to differences in activity level or attraction to the nest but appeared to be perceptual in nature. As adults, animals from large litters showed deficits in learning the 1st 2 problems in a series of visual discriminations in a modified version of the Lashley jumping stand technique in which food reinforcement was not used. The deficits were confined to male animals only and were the result of stronger position habits in the early part of training, rather than an inability to make the discriminations. A comparison of these results with those obtained when other methods of stunting animals are employed revealed that different methods of stunting may result in both common and divergent effects on behavior. One long-term consequence of large litter rearing appears to be increased emotional response to noval situations.