The role of motor activity in children's formation of dynamic mental imagery was investigated in two experiments using a paired-associate recognition task. From the recognition data, it was inferred that (2) the child's ability to form dynamic images relating two objects undergoes its most rapid development between the ages of five and eight; and (b) the preimagery child can generate dynamic mental imagery in which two objects interact if he concurrently engages in overt manipulation of the objects. This is true even when the child has no visual access to his movements or to the objects being manipulated. These results offer strong support for Piaget's theoretical ideas concerning the role of overt and covert activity in the production of mental imagery. (Author/DB)