When the fly flied and when the fly flew: the effects of semantics on the comprehension of past tense inflections

When the Fly Flied and When the Fly Flew: The Effects of Semantics on the Comprehension of Past Tense Inflections Michael Ramscar (michael@cogsci.ed.ac.uk) Division of Informatics University of Edinburgh, 2 Buccleuch Place Edinburgh, EH8 9LW, Scotland. Abstract Although previous theories of past-tense verb inflection have considered phonological and grammatical information to be the only relevant factors in the inflection process (e.g. Bybee & Moder, 1983; Rumelhart & McClelland, 1986; Kim, Pinker, Prince & Prasada, 1991), Ramscar (in press) demonstrated the importance of semantics in processing inflectional morphology. This paper presents an experiment that demonstrates the on-line effects of semantics on inflection. These findings indicate that regular and irregular inflections are determined by semantic and phonological similarities in memory, and furthermore that people are not responsive to the kind of grammatical distinctions amongst verb roots that default rule theories of inflection (Pinker, 1999) presuppose. Introduction In most theories -- and studies -- of past-tense verb inflection, phonological and grammatical information have been considered to be the two relevant factors in the inflection process (e.g. Bybee & Moder, 1983; Rumelhart & McClelland, 1986; Kim, Pinker, Prince & Prasada, 1991; Pinker, 1991; 1999). However, in some models of inflectional processing (MacWhinney & Leinbach, 1991; Joanisse & Seidenberg, 1999), semantic processes have been included to help explain the processing of homophone verbs (e.g. brake/break). Since brake and break both sound the same, phonology alone cannot distinguish which of broke or braked is to be the correct past tense form for the input bre I k . Although using semantic information to guide this process appears intuitively plausible, this suggestion has been fiercely criticised by Pinker and colleagues (Kim et al, 1991; Pinker, 1999), who put forward an alternative, nativist account of homophone inflection (Pinker, 1991; 1999). This predicts that the regularisation of irregular sounding verb stems is driven by innate grammatical sensitivity: verbs that are instinctively perceived to be denominal will be automatically regularised. This account was supported by results reported by Kim et al (1991) which indicate that grammatical factors correlate better than semantic factors with people's ratings of the acceptability of past tense forms in context, although these results did not rule out any semantic role in inflection. However, a recent series of experiments, Ramscar (in press) has demonstrated that the assumption that inflection is driven purely by grammar and phonology is flawed. A series of elicited inflection tasks showed that the semantic context in which a novel verb occurred influenced the forms participants later produced to mark the past tense of that verb. If participants first encountered the novel verb sprink in a context that involved consuming large quantities of fish and vodka (semantically similar to drink), they were likely to produce an irregular past tense form for it (sprank). But if they first encountered sprink in a context which presents as a verb to describe symptoms associated with a disease that involve rapid movements of the eyelid (semantically similar to blink), they were likely to go on and produce a regular past tense form (sprinked). Further, a comparison of the forms participants produced for the nonce verbs sprink and frink in a sparse, eneutrali context (70% irregular) to those produced in the context involving rapid movements of the eyelid (70% regular) showed that the production of regular past tense forms increased when the semantic similarity between sprink and frink and the regular verbs blink and wink was increased. From these results it appears that not only irregular forms can be produced by analogy, but regular forms as well. Semantics versus grammar in homophone inflection Evidence that semantics affects inflection offers a solution to the homophone problem: different forms of homophone verbs are distinguished and computed by reference to their different meaning. Further, Ramscar (in press) contrasted the semantic account of homophone inflection with a nativist attempt to solve this problem put forward by Pinker and colleagues (Kim et al., 1991; Pinker, 1991, 1999, 2001) which predicts that the regularization of irregular sounding verb stems is driven by innate grammatical sensitivity: that any verb that is perceived to be denominal will be automatically regularized, resulting in different inflection patterns for denominal verbs that are phonologically identical to irregular deverbal verbs. Ramscar (in press) found that participantsi sense of the semantic similarities between verb forms correlated strongly with participants preference for a regular or