The results of a group of studies, the objective of which was to clarify the conditions that account for the effectiveness of verbal approbation, are reported. Among the most significant findings were: (1) that the reinforcement properties of verbal approval are susceptible to distortion, misinterpretation or enhancement and must be applied in a consistent information-giving manner; (2) that high prior frequency of occurrence does not necessarily lead to a lowered effectiveness of verbal approval (i.e. satiation); (3) that the pre-experimental indiscriminative use of social approval can override experimental manipulation; and (4) that disapproval words are quite effective, regardless of prior, pre-experimental use, in the control of children's learning. (TL)