The instructional components of mediation, a teaching technique used in dynamic assessment, were evaluated with 100 four-year-old children attending daycare or preschools in London, Ontario. The effects of familiarization with task materials, task-specific rule teaching, and elaborated feedback were assessed using a pretest-posttest design. Children trained on the Stencil Design Test using various combinations of the mediation components were compared to each other and to a non-instructed control group. Analyses of covariance on posttest measures with type of instruction as the independent variable and pretest scores as the covariate revealed that feedback was the most effective component of the mediation procedure. Performance on the Stencil Design Test and near transfer performance on the Animal Stencil Test was significantly better than performance of non-instructed control children whenever feedback was included in instruction on the Stencil Design Test. There was no transfer to the Animal House Coding Task of the Wechsler Preschool and Primary Scales of Intelligence, or to the Conceptual Grouping subtest of the McCarthy Scales of Children's Abilities. Results were discussed in terms of the importance of understanding the nature of the instruction provided in dynamic assessment. (Author/JAZ)