Language development requires, to begin with, that the infant gain the ability to understand and produce identifiable word forms. This talk will focus on the first two years of life, with particular emphasis on the role of vocal practice, not only in production but also in word-recognition and segmentation: Self-action has been found to be a powerful tool for perceptual processing. First word use often reflects implicit mapping of elements of input speech to forms familiar from babble; further support comes from active word learning based on focused attention and episodic memory formation.⠀ ⠀

The next critical step, once an initial expressive vocabulary is in place, is for related forms and meanings to become linked. For this shift to occur the infant’s knowledge and use of word forms must move beyond ‘item learning’, rooted in selection of familiar patterns from the input, to the kind of ‘lexical engagement’ that has been identified in adult word learning. For infants, this can be observed when phonological patterns underlying individual representations are extended to new, more challenging word forms, which are adapted to the child’s patterns in accordance with one or more emergent templates. I will show that child templates integrate aspects of the ambient language structure with the individual child’s own well-practiced production routines. ⠀

These first steps toward lexical systematicity lay the foundation for the basic linguistic principle of opposition of structures. Reaching this point requires that ‘secondary’ distributional learning (a type of implicit memory, here operating over the database constituted by the individual child’s history of word use) complement word learning with attention . The extension or generalization of lexical representations reflects the interaction of complementary memory systems; it is the interaction of implicit and explicit learning that makes the acquisition of this uniquely complex human behaviour possible.