Brain potentials to inflected adjectives: Beyond storage and decomposition

This study uses event-related brain potentials (ERPs) to investigate the temporal sequencing of structural (grammatical) and lexical (semantic) properties of complex words during language comprehension. Morphologically complex words do not only consist of stems and affixes (e.g., 'feel'+'-s'), but affixes also contain grammatical structure, viz. feature bundles specifying their morpho-syntactic functions (e.g., -s= [3rd person, singular, present tense]). We examined inflected adjectives of German, which consist of an unaltered stem plus a portmanteau affix encoding case, number and gender. The same group of 24 adult native speakers was tested in two cross-modal ERP priming experiments separately studying effects of lexical-semantic relatedness and related affixes. The results of these experiments revealed clearly distinct brain potentials. Prime-target overlap with respect to morpho-syntactic features was associated with a reduced positivity, whereas lexical-level priming led to a reduced negativity. The former was most pronounced between 200 and 300 ms and the latter in a later time window, between 300 and 400 ms. We interpret the reduced early positivity as reflecting ease of grammatical processing effort in case of primed (relative to unprimed) morpho-syntactic features and the reduced negativity as signaling facilitation in lexical retrieval for primed (compared to unprimed) words. Our ERP results indicate that grammatical information becomes available earlier than semantic information providing support for structure-first models of language processing.