Processing inflectional morphemes: Effects of segmentation difficulty, regularity, and frequency

The distinction between regular versus irregular inflectional morphology is a focal point in psycholinguistic inquiries into the structure of the lexicon. Theories generally fall into two camps—dual-mechanism, which postulates rules for regulars and memory or associative nets for irregulars, and single-mechanism (including connectionist models), which handle regulars and irregulars in the same system.; This dissertation examines regularity in English noun-noun compounding. Generally, irregular but not regular plurals are allowed as first elements of such compounds (mice trap, *rats trap). Dual-mechanism theorists attribute this dichotomy to the theory of level ordering of morphology, which postulates a strict demarcation between regulars and irregulars. Because children readily produce this pattern (Gordon, 1985), it is cited as support for innateness of grammar.; I propose an alternative explanation: Speakers attempt to use singulars in compounds, but differences in processing difficulty between regulars and irregulars, rather than regularity per se, lead to differences in production. Processing difficulty may stem from different degrees of similarity between singular and plural forms for regulars versus irregulars, leading to differences in difficulty in accessing one form from the other—in compound formation and in general.; Four experiments test this hypothesis. In Experiments 1 and 2, adults produced noun-noun compounds in a task like Gordon's. Similar patterns were observed, and it took longer to produce an irregular singular from its plural form than in any other case. In Experiments 3 and 4, participants saw a picture of one or several objects and a number indicating singular or plural response. The picture and required response numbers either matched or not. Experiment 3 used English; Experiment 4 used a miniature artificial language, controlling frequency, word form, and pluralization method. In both experiments responses took longer when the picture and required response numbers did not match.; Thus the results in noun-noun compounding can be explained within a single-mechanism model by the fact that it is harder to access an irregular singular from its plural than it is for regulars—with no need to rely on level ordering or innateness as an explanation.