GENETIC AND SOCIAL CAUSES OF AGGRESSIVE BEHAVIOUR IN MICE

L agerspetz , K irsti . Genetic and social causes of aggressive behaviour in mice. Scand. J. Psychol ., 1961, 2 , 167—‐173.—Significant differences in the aggressiveness of mice selected for aggressiveness and non‐aggressiveness have been found to occur in the 2nd and 3rd generation of selective breeding. In S a , motor activity scores were significantly higher in mice of the aggressive than of the non‐aggressive strain. Defecation and ambulation scores obtained both in a standardized open‐field test and in connection with the aggression measurements showed that the S 3 descendants of the aggressive mice were emotionally less reactive than the members of the 3rd non‐aggressive generation. Defeats tend to decrease, victories to increase the level of aggressiveness in mice, but the aggression scores tend to return to the original level after the termination of the experiments.