Sixteen middle class, four-person families were used in a study comparing communicative behavior of parents interacting with a younger child (3 or 4 years old) whose language skills were developing, and with an older child (6 or 7 years old) whose basic language skills were established. Combinations of sex of siblings and sibling position were balanced. Interactions of parents teaching one child at a time how to put four puzzles together were tape recorded, and each child was tested individually to ascertain his language skills. Five-minute segments extracted from each of 32 recorded interactions provided typescripts from which dialogues were divided into units--any remark that could stand alone. Two trained judges and the experimenter assigned the units to one of five categories, the most frequently used of which was "remark requiring response," with "positive feedback" second in frequency. Also studied were (1) who talked to whom, and (2) the number of units and the number of speeches emitted by each person. Findings showed that (1) fathers tended to dominate interactions involving parents and younger siblings, and parents and male siblings; and (2) mothers tended to dominate interactions involving older siblings and female siblings. (Author/JMC)