Attribution Theory has led to predictions that the use of material reward may impair intrinsic motivation in the rewarded activity (decreased play effects). A review of the pertinent literature reveals, however, (a) that attribution research has failed to reliably demonstrate that decreased play effects occur in minimal-trial studies (b) that for what effects are reported, alternative and more plausible explanations are available; and (c) that reinforcement programs (multiple-trial studies) do not produce decreased play effects beyond chance levels. Implications and recommendations based on the review are offered. (Author)