This book explores the effect of speech perception strategies upon morphological structure. Using connectionist modelling, perception and production experiments, and calculations over lexical, Jennifer Hay investigates the role of two factors known to be relevant to speech perceptions: phonotactics and lexical frequency. Hay demonstrates that low-probability phoneme transitions across morpheme boundaries exert a considerable force toward the maintenance of complex words, and argues that the relative frequency of the derived form and the base significantly affects the decomposability of complex words. While many have claimed that high frequency forms do not tend to be decomposed, Hay asserts that this follows only when such forms are more frequent than the bases they contain. The results of Hay's experiments illustrate the tight connection between speech processing, lexical representations and aspects of linguistic competence. The likelihood that a form will be parsed during speech perception has profound consequences, from its grammaticality as a base of affixation, through to fine details of its implementation in the phonetics.