When the fly flied and when the fly flew: How semantics affect the processing of inflected verbs
2012-03-20

Abstract 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. Keywords: SemanticsPast-tense inflectionPredictionDiscrimination Acknowledgments We are grateful to Ulrike Hahn, Scott McDonald, Mark Steedman, Lera Boroditsky, Daniel Yarlett, Benjamin Hersh, and Stewart McCauley for many helpful discussions. Thanks to William O'Connor for help in piloting Experiment 1, and to British Airways and the Boeing Corporation for inspiration. Notes 1In devising the sample tested here, we took into account the comparative rarity of the lexical population under consideration. In English, there is a limited number of irregular verb clusters, and a correspondingly small number of homophone verb pairs. Indeed, there are likely no more than a handful of cases in which an existing lexical item can be presented in novel noun and verb forms with irregular or regular past tenses. Given that sample sizes should be matched to the size of the sampling population, four items provide a representative sample here. 2Such a stance would almost certainly be problematic for dual-route theorists, as it directly contradicts the claim that "denominal verbs ... have regular past tense forms, even if homophonous with, or ultimately derived from, an irregular verb" (Kim et al., Citation1991, p. 179). 3"Intuitions of which member of a noun/verb pair is basic presumably involve the semantics of the noun/verb distinction, such as the distinction between entities on the one hand and events or states on the other. For example, "an easy read" can plausibly be thought of as meaning something that is easy for people to read, but "to read the book" cannot easily be thought of as having been derived from the noun read." (Kim et al., Citation1991) 4A discriminative learning account can make sense of many of the findings in early childhood language development. For instance, in the case of irregular plurals, the tendency for children to over-regularise can be modeled as a lack of semantic discrimination between plural nouns, which initially leads to strong expectation for a regular phonological form, but eventually resolves over the course of discrimination learning (see e.g., Ramscar & Dye, Citation2009; Ramscar & Yarlett, Citation2007). Similarly, a learning model can account for why nouns and verbs "with greater irregular cluster strength (as measured by the number and frequency of similar neighbors) [are] less prone to overregularisation" (Marcus, 1996, p. 82); in a discrimination network, phonological clusters (groups that take the same irregular ending) should be discriminated significantly faster than single idiosyncratic items, resulting in reduced rates of overregularisation.