The effectiveness of social modeling reinforcers in changing the toy preferences of preschool-age children was investigated in this document. Subjects, ranging in age from 37 to 64 months, were matched by sex and age, then randomly assigned to one of two experimental conditions or to one control condition. In the high-reinforcement condition the experimenter was expressive, inquisitive, proximate, and nurturant; in the low-reinforcement condition she was neutral, calm, relaxed, and expressionless. In the control condition the experimenter left the room and observed the child at play. Four reinforcers (affect, reward, proximity/distance, and nurturance) were assumed to be operating jointly and vicariously in the two experimental conditions. After determining the child's preferences for three toys, the experimenter announced that the subject could play with any one of them. In the two experimental conditions the experimenter played with the toy the child preferred least. Once during the 5-minute play period the subject was given an opportunity to select another toy from the complete set of three. Results concerning the effects of social modeling reinforcers, sex, and age on change in toy preference are discussed. Related materials are appended. (RH)