[Effects of post-weaning rearing conditions on learning performance in "dwarf" mice (author's transl)]

The effects of different environments on learning ability were investigated in mice homozygous for the locus "dwarf," characterized by a primary deficiency of the anterior hypophysis. Two experiments were conducted; they differed from one another in several aspects such as sex and age at entry into different environments. In both experiments, half the "dwarf" (homozygous dw/dw) and control mice of the same strain (heterozygous dw/+ or homozygous +/+) were placed in either an "enriched" or "impoverished" environment. After 31 days of rearing in these conditions, animals were then pretrained and tested with the standard 12 Hebb-Williams problems. Results from both experiments revealed that (1), independently of environment, "dwarf" mice made significantly more errors than controls (p less than 0.001); (2) mice of the "enriched" groups made significantly less errors than those of the "impoverished" groups (p less than 0.05); (3) environmental effects tended to be larger in "dwarf" mice than in controls. The results are discussed in the light of previous observations on the level of locomotor activity and on the degree of interaction of "dwarf" mice with their physical environment; they are compared to those reported for hypothyroid animals and to those of animals with hippocampal lesions.