Assessed the interpersonal interaction and task performance of children in a cross-age tutoring situation. Ss were 48 elementary school pupils. 5th and 6th graders acted as tutors for the 1st and 2nd graders. In the reward condition, 12 6th-grade girls were promised movie tickets for successfully teaching a sorting game to a 1st-grade girl. In the no-reward condition, Ss taught the game without promise of reward. Ss were randomly assigned to pairs and conditions. Results indicate more criticism, more demands, and less efficacious use of time in the reward condition. The no-reward condition was marked by a more positive emotional tone, greater learning by younger Ss, and fewer errors. Results are viewed as evidence that anticipation of reward generates an "instrumental orientation" that has deleterious social effects. (PsycINFO Database Record (c) 2016 APA, all rights reserved)