LAWRENCE, BARBARA M. Conversation and Cooperation: Child Linguistic Maturity, Parental Speech, and Helping Behavior of Young Children. CHILD DEVELOPMENT, 1984, 55, 1926-1935. The relationship between parental communicative behaviors, child linguistic maturity, and children's cooperative behavior was examined in a study of 60 children (20 each at approximately 18, 24, and 30 months of age) and their parents in a laboratory setting. Significant relationships were found between linguistic maturity of the children, the speech of the parents, and the children's helping behavior. Child mean length of utterance (MLU) was a better predictor of cooperative behavior than child age. No comparable relationships were found for parents' nonverbal behaviors. The results support a hypothesis of verbal mediation of this social behavior.