Blurb:

This article deals with a famous case of allomorphy in Italian, the so called mobile diphthongs, a vowel alternation in the roots of inflectionally or derivationally related words. It is argued that the two allomorphs have to be lexically listed. The selection of the right allomorph is performed by the language-specific ranking of a set of universal phonological output constraints, as assumed in Optimality Theory. Proper assumptions about the balance between storage and computation of phonological information, in combination with a model of phonological computation in which allomorphs are listed and a set of ranked output conditions select the optimal allomorph provide an insightful account of the Italian mobile diphthongs, both from a synchronic and a diachronic perspective.