The role of domain-general inhibition in inflectional encoding: Producing the past tense

According to a prominent account of inflectional encoding (Pinker, 1999; Pinker & Ullman, 2002b), regular forms are encoded by a rule-governed combination of stems and affixes, whereas irregular forms are retrieved from memory while inhibiting rule application. Sahin, Pinker, and Halgren (2006) suggested that this concerns a domain-general mechanism. Previous research on domain-general inhibition has shown that when switching between tasks, languages, or phrase types, an asymmetrical switch cost is obtained, which has been attributed to overcoming previous inhibition of the predominant response. If generating an irregular form involves rule inhibition, then switching from an irregular to a regular form should require overcoming previous inhibition and delay responding. We tested this in three experiments on producing the past tense in Dutch. We observed that an asymmetrical switch cost is obtained when switching between inflecting and reading verbs, but not when switching between encoding irregular and regular forms. These results suggest that the production of irregular forms does not involve the type of domain-general inhibition involved in switching between tasks, languages, or phrase types.