Children's spoken word recognition is little understood compared to our knowledge of the adult system. We present here a combined experimental and computational exploration of the development of lexical access. Three accounts of the way children represent lexical form (Full-Specification, Radical Underspecification and Gradual Segmentation) are rejected in favour of one which derives from a connectionist approach. It sheds light on the pattern of results from two experiments investigating the way children, aged 5- to 9-years-old, process regular and irregular variation in the surface form of speech, which suggested, whilst children's lexical representations are functionally underspecified from at least 5-years-oId, they are only beginning to track the viability of regular phonological variation at 9-years-old. The late acquisition of phonological inference is accounted for in a connectionist model in terms of the sparseness of the information relevant to learning this structural relationship in language.