When the fly flied and when the fly flew: How semantics affect the processing of inflected verbs

Although psychological theories of inflectional morphology have traditionally considered phonological and grammatical information to be the only factors affecting inflection, there is ample evidence indicating that semantic information can play a vital role in determining the past-tense forms of homophone verb stems. In this paper, we present two experiments that use on-line measures to test the prediction that semantic context shapes readers' expectations about the past-tense form of an upcoming verb. Consistent with the predictions of “single-route” accounts that model inflection using a uniform process of comparison to stored forms in memory, and contrary to the predictions of theories that posit context-independent rules, semantics are found to strongly influence reaction time data for both irregular and regular verbs, and for both existing and nonce verb forms. At the same time, no dissociation between regular and irregulars is observed, a finding which undercuts “dual-route” arguments for a grammatical constraint on denominal verb inflection. We discuss how these results may be understood in terms of discrimination learning.