The role of meaning in inflection: why the past tense does not require a rule.

How do we produce the past tenses of verbs? For the last 20 years this question has been the focal domain for conflicting theories of language, knowledge representation, and cognitive processing. On one side of the debate have been similarity-based or single-route approaches that propose that all past tenses are formed simply through phonological analogies to existing past tenses stored in memory. On the other side of the debate are rule-based or dual-route approaches which agree that phonological analogy is important for producing irregular past tenses (e.g., think-->thought), but argue that regular past tenses (e.g., walk-->walked) are generated via a +ed rule and that a principled account of regular inflection can only be given by recourse to explicit rules. This debate has become a crucial battleground for arguments concerning the necessity and importance of abstract mental rules, embracing not only language processing, but also the of nature cognition itself. However, in centering on the roles of phonological similarity and rules, the past tense debate has largely ignored the possible role of semantics in determining inflection. This paper presents five studies that demonstrate a striking and decisive role of semantic similarity in inflection. In fact, semantic factors appear to be more important in inflection than the grammatical considerations put forward by the dual-route account. Further, these new findings provide a new way of discriminating between the claims of single-route (similarity-based) and dual-route (rule-based) approaches. It appears that inflection is carried out through analogical reminding based on semantic and phonological similarity and that a rule-based route is not necessary to account for past tense inflection.