The processing of English regular inflections: Phonological cues to morphological structure

Previous studies suggest that different neural and functional mechanisms are involved in the analysis of irregular (caught) and regular (filled) past tense forms in English. In particular, the comprehension and production of regular forms is argued to require processes of morpho-phonological assembly and disassembly, analysing these forms into a stem plus an inflectional affix (e.g., {fill}+{-ed}), as opposed to irregular forms, which do not have an overt stem+affix structure and must be analysed as full forms [Marslen-Wilson, W. D., & Tyler, L. K. (1997). Dissociating types of mental computation. Nature, 387, 592-594; Marslen-Wilson, W. D., & Tyler, L. K. (1998). Rules, representations, and the English past tense. Trends in Cognitive Science, 2, 428-435]. On this account, any incoming string that shows the critical diagnostic properties of an inflected form - a final coronal consonant (/t/, /d/, /s/, /z/) that agrees in voicing with the preceding segment as in filled, mild, or nilled - will automatically trigger an attempt at segmentation. We report an auditory speeded judgment experiment which explored the contribution of these critical morpho-phonological properties (labelled as the English inflectional rhyme pattern) to the processing of English regular inflections. The results show that any stimulus that can be interpreted as ending in a regular inflection, whether it is a real inflection (filled-fill), a pseudo-inflection (mild-mile) or a phonologically matched nonword (nilled-nill), is responded to more slowly than an unambiguously monomorphemic stimulus pair (e.g., belt-bell). This morpho-phonological effect was independent of phonological effects of voicing and syllabicity. The findings are interpreted as evidence for a basic morpho-phonological parsing process that applies to all items with the criterial phonological properties.