Crucial periods for free-environmental experience in the rat.

Abstract

Psychologists have known for some time that the type of early experience provided an animal can influence his adult performance on a variety of tasks (Beach & Jaynes, 1954). Recently, researchers (Bingham & Griffiths, 1952;Forgays & Forgays, 1952; Fergus, 1954; and others) have demonstrated that rats reared in large complex environments are superior in problem-solving ability to rats reared under more restricted conditions. In addition, Hymovitch (1952) found evidence indicating that the enriched experience must occur before maturity if it is to lead to the reported effect. In a study using form discrimination as the response measure, Fergus (1954) reported that the enriched experience must occur extremely early in the life of the rat. In this latter study, testing of the two groups of animals constituting the design was accomplished well before full maturity of the rats so that in this sense, at least, the results cannot be compared directly with those of Hymovitch.As yet there has not been reported a systematic investigation of several quite important aspects of the early-experience issue; namely, just how much experience is necessary in these complex environments to produce a superior adult animal, and when, specifically, during early life must this experience occur, assuming that it must take place before full maturity. A still more interesting matter is the interaction of these two dimensions, that is, the possibility that a greater amount of experience occurring during one developmental period produces the same results in the adult animal as a smaller quantity of such experience during another period. Moreover, it would be desirable in any such studies to examine the functioning of the adult animals on a variety of intellectual, emotionality, and other measures.The present study is an attempt to investigate in part the second of the issues raised above; that is, When, specifically, during the relatively short maturation period of the

Effects of preweaning environmental enrichment on later problem-solving behavior in rats

“…These findings generally agree with previous observations 1968;Forgays & Reid, 1962), but indicate that a period of exposure considerably shorter than that used previously can have beneficial effect on PSB in rats: The results also show that additional handling dunng the preweaning period (which is expected to decrease emotionality) did not have any significant effect on PSB, and this is in agreement with the findings reported by Denenberg and Morton (1962). In fact, rats that were handled in this experiment performed at the same level on Hebb-Williams problems as did control animals.…”

“…It is worth noting, in this context, that Forgays and Reid (1962) obtained preweaning enrichment effects when the rats were tested after 100 days and that Denenberg et at. (1968) obtained similar results after 350 days.…”

“…The period of exposure is shorter than that used by Denenberg et al (1968) and Forgays and Reid (1962). However, it is during this period when the infant rats become more mobile and the auditory and visual systems develop more fully.…”

“…Forgays and Reid (1962) report that rats exposed from 0 to 21 days to an enriched envrionment performed better than control rats, and they concluded that very brief exposure in a wider environment in early life can have rather lasting effects. Haywood and Tapp (1966) suggested that stimulation during the 15-to 20-day period could alter rodents' later capacity for problemsolving.…”

“…More specifically, the optimum postweaning period for enriched stimulation in rats has been suggested to be between 22 to 43 days (Forgays & Reid, 1962) and between 50 to 60 days (Nyman, 1967). However, enriched experience before weaning (e.g., 0-21 days) can also significantly imRequests for reprints should be sent to Dr. A. Ivinskis, Department of Psychology, University of Newcastle, Newcastle, New South Wales 2308, Australia.…”