Key points are not available for this paper at this time.
Andrew F. Newcomb, Judith E. Brady, Willard W. Hartup, Friendship and Incentive Condition as Determinants of Children's Task-Oriented Social Behavior, Child Development, Vol. 50, No. 3 (Sep., 1979), pp. 878-881
Newcomb et al. (1979) studied this question.