When does a writing system emerge out of children's drawing to separate (a) script processing and production from (b) picture processing and production? And does one system's activation help or hinder the other system's operation? Children 4-12 years of age wrote repeated Os and Vs and drew matching shapes, in the contexts of script and of pictures. The technique elicits matching products in order to identify differences between production kinematics in different contexts. A transition occurred around age 6 in which (a) production was more fluent for writing than drawing and (b) activation of one system interfered with the other. Modeling the consolidation of both phenomena generated testable parameters for the slow approach to the adult steady state, involving increasing specialization and the waning of the need for suppression of the two systems' interference.