EARLY EXPERIENCE AND DEVELOPMENT OF MOUSE KILLING BY RATS

64 rats reared in social isolation after weaning and 32 litter-mate controls reared in groups of 4 were tested for mouse killing when 4-mo-old. Although isolated Ss were somewhat awkward and poorly coordinated in their attacks, the proportions of killers in the 2 groups did not differ significantly. In Exp. II 25 rats were repeatedly exposed to mice from weaning until they were 5 mo. 25 litter-mate controls were not exposed to mice. At 5 mo., both groups were isolated for 10 days, then tested for killing. 54% of the controls and 9% of the experimental group were killers. After testing, the Ss were returned to their rearing cages for 2 mo., during which neither group was exposed to mice. They were then retested. Killing was exhibited by 73% of the controls and only 14% of the experimental group. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.