Decomposition of morphologically complex words in English: evidence from event-related brain potentials

To explain processing differences between regular (e.g., start/started) and irregular (e.g., think/thought) word formation linguistic models posit eit her a single mechanism handling both morphological clusters or separate mec hanisms for regular and irregular words. The purpose of the present study i s to investigate how these processing differences map onto brain processes by assessing electrophysiological effects of English past tense forms, usin g the repetition priming paradigm. Event-related brain potentials (ERPs) we re recorded from 59 scalp sites as 19 subjects read stem forms of regular a nd irregular verbs from a List of 1152 words; the stem forms were either pr eceded (5-9 intervening items) by their past tense forms (= primed conditio n) or by past tense forms of unrelated verbs (= unprimed condition). The di fference between the ERPs to the primed and unprimed stems was taken as a m easure of morphological priming. We found that the ERPs to regular verbs we re clearly different from those to irregular verbs: the former were associa ted with an N400 reduction in the primed condition; primed irregular verb s tems, however, showed no such effect. Control conditions demonstrated that the N400 modulation for regular verbs cannot be attributed to formal (i.e., phonological or orthographical) priming. These ERP effects indicate that r egular verbs serve as more powerful primes for their corresponding stem for ms than irregular past tense forms, suggesting that regular (but not irregu lar) past tense forms may be decomposed into stem plus affix. (C) 1999 Else vier Science B.V. All rights reserved.