Human brain potentials indicate morphological decomposition in visual word recognition.

Stem homographs are pairs of words with the same orthographic description of their stem but which are semantically and morphologically unrelated (e.g. in Spanish: rata/rato (rat/moment)). In priming tasks, stem homographs produce inhibition, unlike morphologically related words (loca/loco (madwoman/madman)) which produce facilitation. An event-related potentials study was conducted to compare morphological and stem homographic priming effects. The results show a similar attenuation of the N400 component at the 350-500 ms temporal window for the two conditions. In contrast, a broad negativity occurs only for stem homographs at the 500-600 ms window. This late negativity is interpreted as the consequence of an inhibitory effect for stem homographs that delays the stage of meaning integration.