Community life and the development of avoidance reaction in the laboratory rat.

The development of learning of active avoidance reaction in laboratory rats was studied in the course of the juvenile period, sexual maturation and in adulthood. The ability of acquiring and extinguishing an active avoidance reaction during the juvenile period is determined by the way of life: life in a community, at least during the suckling, weaning, or juvenile period positively influenced the ability of the animals to extinguish the reaction while the rate of acquisition slowed down. During learning a balance was thus reached between the rate of acquisition and extinction. In the young reared exclusively in presence of their mother and siblings, the rate of acquisition of this reaction was higher, and the ability of extinguishing was both qualitatively and quantitatively worsened. Thus the relation between the process of excitation and inhibition became unbalanced. In the period of sexual maturation and in adulthood community life had no effect on acquisition and extinction. It had, however, a late effect in those animals which were reared until weaning in a community: in the adulthood a positive correlation was detected between their rate of acquisition and extinction. In contrast, in adult animals reared until weaning in the presence of their mother and siblings, the correlation was found to be negative.