The present paper analyses the slot filler's function in the categorization process and especially its role of conceptual precursor. 3-and-5-years-old subjects were compared. Two slot filler lists - functional/paradigmatic/replaceable/alternate and co-ordinate/sintagmatic/complementary/contiguos - were used, after three training's sections. Both lists were presented in four different modalities of instructions: scripted, categorical, attentional and incidental. The result show no substantial differences among the two lists in the first rehearsal, but differences in the deferred rehearsal after the training.