Poster E50, Thursday, August 22, 2019, 3:45 – 5:30 pm, Restaurant Hall
The role of inhibition in inflectional encoding: Producing the past tense
João Ferreira1, Ardi Roelofs1, Vitória Piai1,2;1Radboud University, Donders Centre for Cognition, 2Radboudumc, Donders Institute for Brain, Cognition, and Behaviour, Department of Medical Psychology
According to a prominent account of inflectional encoding (Pinker, 1999; Pinker & Ullman, 2002), regular forms are encoded by a rule-governed combination of stems and affixes, whereas irregular forms are retrieved from memory while inhibiting rule application. Previous research has shown that when speakers switch 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 inhibition of rule application, then switching from an irregular to a regular form should require overcoming previous inhibition and delay responding. Using this rationale, in a first experiment participants alternated between producing regular and irregular past tenses in Dutch. The infinitive form of a verb was presented on a screen and participants were instructed to produce the first-person singular past-tense form of the verb as quickly and accurately as possible. A microphone recorded the onset of their response and an experimenter outside the booth registered manually whether each response was correct. The order of trials was pseudorandomized, with two regular verbs followed by two irregular verbs, and so forth. In a second experiment, and to attest that our stimuli were strong enough to yield an asymmetrical switch cost, participants alternated between inflecting and reading aloud. Procedure was similar to the first experiment, with the addition of a colored frame around the word cuing participants to which task to perform. As with the first experiment, task changed with every second trial. Regulars and irregulars were presented in small “mini-blocks” of 24 trials of the same regularity type, hence switching costs in the second experiment concern task and not verb regularity. In the first experiment we found no difference in RT between producing regulars and irregulars, and also no switch costs: production of a verb of one regularity was not affected by the regularity of the previous trial. In the second experiment participants were slower on the inflect compared to the read trials. Crucially, for the read task participants were slower on the task switch than on the task repeat trials, with no difference between regulars and irregulars. Thus, an asymmetrical switch cost was obtained for switching between tasks, but not for switching between irregulars and regulars. Our findings challenge the assumption that inhibition is the mechanism by which rule application is blocked in producing the past tense of irregular verbs. Importantly, we examined inhibition by looking at the effect of overcoming previous inhibition. That is, if producing an irregular on a trial involves inhibition of rule application, then switching from an irregular to a regular on the next trial would require overcoming the inhibition of the rule on the previous trial, which should delay responding. It might still be the case that inhibition is involved in irregular production but is not strong enough to affect the next trial. In an ongoing neuroimaging study we investigate the hypothesis of rule inhibition more directly by measuring the hemodynamic reflection of inhibition during the encoding of irregulars itself.
Themes: Language Production, Morphology
Method: Behavioral