A positron emission tomographic study of regular and irregular verb morphology in English

Theories about the representation and processing of regular and irregular past tense forms of verbs in English have disagreed as to whether they should be treated as a unified phenomenon (e.g. both rule-governed, or both generated by a connectionist net), or as two distinct types of linguistic entities (e.g. regulars formed by rules of the grammar, irregulars stored in lexical memory). In this article we present data from a positron emission tomographic study in which subjects were asked to produce the past tense forms of regular, irregular, and nonce stems. We find very different amounts and areas of cortical activation in the regular and irregular tasks, as well as significantly different reaction times in producing the past tenses. We interpret our findings as supporting the grammar/lexicon theories, and discuss the implications of our results for general linguistic theory.