The block building, Lego construction, pen drawing, and painting of four preschool children were analyzed in terms of the construction of form diversity and new form production. Social descriptive reinforcement, contingent on the production of any form not previously constructed within the current session and overt modeling of forms never seen produced during the study, increased form diversity scores per session and new form production (forms never seen before in the child's total prior sequence of blockbuilding sessions). The results indicated that after training, form diversity scores generalized to topographically similar and dissimilar media of expression. New form production generalized to topographically similar and dissimilar media in the majority of the children.