In 2 groups of rats, one living in groups of 6 to a cage and the other consisting of single rats in isolated cages, 18 of 124 in the first group manifested "freezing". Only 2 rats in the 2d group displayed this behavior. The only major difference was found to lie in the manner of housing which emphasized dominance and submission, the "frozen" animals being the more submissive. Behavior depended upon social environment.