Social factors affecting emotionality and resistance to disease in animals: III. Early weaning and susceptibility to gastric ulcers in the rat. A control for nutritional factors.
Rats were subjected to a conflict situation in adulthood after receiving 1 of 3 early treatments: removal from the mother at the usual age of 21 days, removal at 15 days, or removal from mother at 21 days but without having been permitted to suckle since 15 days. In opposition to the suggestion that a dietary effect underlies the effect of early separation, more ulcers were found in the 15-day-removal group than in either of the other groups. This difference was found only in males: "the basic interaction between a mother rat and her offspring . . . [may be] different for males and females." (PsycINFO Database Record (c) 2006 APA, all rights reserved)