Single- and Dual-route Models of Inflectional Morphology

Abstract

Abstract Rather than reduplicate every item in the lexicon for number and gender, human languages have regular systems of phonological changes that systematically mark changes in these attributes. Various theories have been put forward to define how these systems operate and how they are acquired. Here we will concentrate on just one aspect of inflectional morphology—whether the system is best described as a single-route or a dual-route mechanism. In contrast to connectionist models of inflectional morphology that have argued for a singleroute mechanism (Rumelhart and McClelland 1986, Plunkett and Marchman 1991), Pinker (1991) states that inflectional morphology in all human languages is computed by a dual-route mechanism consisting of a pattern associator and a rule. During the course of acquisition, one type of inflection is identified as a ‘default’ and this form is produced by the rule-route whenever the pattern associator memory fails. If a word is similar to a known irregular, however, the pattern associator produces the appropriate irregular form and blocks action of the rule. For example, when producing the plural of the regular word dog, the rule route produces the plural dogs and the pattern associator has no irregular entry for the singular form, and so does not block production of dogs. For the irregular word sheep, the pattern associator produces the irregular plural sheep and the rule, which erroneously produces the form sheeps, is blocked (see Figure 10.1).