Effects of incubator rearing with social deprivation on maternal behavior in rats.

A procedure for rearing infant rats separated from the mother on the day of birth was developed and used to study effects of preweaning deprivation of mother and peers on subsequent maternal behavior. Holtzman albino females were reared for Days 1-25 of life with or without peers, and in an incubator or with a mother. At maturity, following mating and parturition, there was very little difference among the groups on directly observable maternal behaviors. However, offspring of incubator reared Ss showed a higher mortality rate and a significant delay in eye-opening. For mammals, it would seem likely that social experience prior to weaning should be an important variable affecting later behavior. In particular, it would seem likely to affect later maternal behavior. At the primate level, Harlow (1962) has found that monkeys separated from the mother at birth and reared alone were quite inadequate when they became mothers. He found further that for normal social development, play with peers was even more important than mothering. At the rat level the need to study preweaning social deprivation has been recognized by numerous investigators, but heretofore it was not possible to make such studies because there was no way to maintain the lives of the animals in the absence of the mother. Lacking an adequate artificial rearing technique, previous Es have had to compromise in various ways. Beach (1937) studied the effects of early social deprivation on maternal behavior in the rat, but variation in rearing conditions was introduced after animals were weaned. When Guze (1955) studied the same experimental variables, using partial isolation during the nursing period, Ss suffered greatly from inanition and many of them