Hemispheric sensitivity to grammatical cues: evidence for bilateral processing of number agreement in noun phrases

The present experiment employed a grammatical priming task to explore the possible contributions of the left and right cerebral hemispheres to the processing of grammatical agreement. Stimuli were three-word noun phrases, with the prime centered above the fixation point and the target presented laterally to one visual field after a 600-ms stimulus onset asynchrony. Number agreement between primes and targets was varied such that the article of the prime could be consistent (i.e., each narrow shoe or all narrow shoes), inconsistent (i.e., all narrow shoe or each narrow shoes) or neutral (i.e., the narrow shoe(s)) with respect to the inflection of the target. Half of the subjects provided lexical decision responses and the other half pronunciation. The bilateral priming effect, obtained only in lexical decision, suggests that both the left and the right hemispheres are sensitive to certain grammatical cues. In addition to the task difference in priming, the inclusion of a neutral condition and of pseudo-inflected nonwords allowed these effects to be attributed to postlexical mechanisms.