Rules or connections in past-tense inflections: what does the evidence rule out?

Pinker and colleagues propose two mechanisms - a rule system and a lexical memory - to form past tenses and other inflections. They predict that children's acquisition of the regular inflection is sudden; that the regular inflection applies uniformly regardless of phonological, semantic or other factors; and that the rule system is separably vulnerable to disruption. A connectionist account makes the opposite predictions. Pinker has taken existing evidence as support for his theory, but the review of the evidence presented here contradicts this assessment. Instead, it supports all three connectionist predictions: gradual acquisition of the past tense inflection; graded sensitivity to phonological and semantic content; and a single, integrated mechanism for regular and irregular forms, dependent jointly on phonology and semantics.