Bobo clown aggression in childhood: Environment,not genes

We videotaped 216 twin children (average age: 7.6 years) hitting a 5-ft “Bobo clown”. Three behaviors in the Bobo clown situation showed adequate response characteristics, rater reliability, and test-retest reliability: number of hits, intensity of hits, and number of quadrants (into which the Bobo clown was hit). In terms of two “anchor” variables, height and weight, the twin correlations were representative of other studies in suggesting substantial hereditary influence. However, twin analyses of the three behavioral ratings during the Bobo clown session yielded no evidence of hereditary influence. Moreover, the results provided evidence of substantial environmental influence of the “between-family” variety. In other words, the family environment is the major source of individual differences for these measures.