Litter Size, Emotionality, Learning, and Social Interaction in C57Bl/6J Mice

Activity in the open field, weight, escape learning, and social interaction were assessed as a function of amount of stimulation during the preweaning period in C57BL/6J mice. The results showed that subjects in small litters (5 pups) were more active and had shorter latencies to cross the first square in the open field than subjects in large litters (10 pups). The social-interaction task indicated that subjects in large litters had shorter latencies to initiate body contact. However, no differences in weight or escape learning were reported. Competition for nipple sites, the amount of maternal behavior, and expectancy of contact were described as possible variables affecting the performance of subjects reared in large and small litters.