The extent to which the processing of compounds (e.g., “catfish”) makes recourse to morphological-level representations remains a matter of debate. Moreover, positing a morpheme-level route to complex word recognition entails not only access to morphological constituents, but also combinatoric processes operating on the constituent representations; however, the neurophysiological mechanisms subserving decomposition, and in particular morpheme combination, have yet to be fully elucidated. The current study presents electrophysiological evidence for the morpheme-based processing of both lexicalized (e.g., “teacup”) and novel (e.g., “tombnote”) visually-presented English compounds; these brain responses appear prior to and are dissociable from the eventual overt lexical decision response. The electrophysiological results reveal increased negativities for conditions with compound structure, including effects shared by lexicalized and novel compounds, as well as effects unique to each compound type, which may be related to aspects of morpheme combination. These findings support models positing across-the-board morphological decomposition, counter to models proposing that putatively complex words are primarily or solely processed as undecomposed representations, and motivate further electrophysiological research toward a more precise characterization of the nature and neurophysiological instantiation of complex word recognition.

Whether morpheme-based processing extends to relatively unproductive derived words remains a matter of debate. Although whole-word storage and access has been proposed for some derived words, such as Japanese de-adjectival nominals with the unproductive (-mi) suffix (e.g., Hagiwara et al. in Language 75:739-763, 1999), Clahsen and Ikemoto (Ment Lex 7:147-182, 2012) found masked priming from de-adjectival nominals with productive (-sa) and unproductive (-mi) suffixes to their adjectivally-inflected base morpheme. Using masked and unmasked priming, we examine whether adjectivally-inflected base morpheme primes facilitate the processing of Japanese de-adjectival nominal targets with a productive or unproductive affix, including an orthographic-overlap condition and semantic relatedness measure that Clahsen and Ikemoto (2012) did not include. Our results replicate and extend Clahsen and Ikemoto (2012), revealing significant, statistically-equivalent morphological priming effects for -sa and -mi affixed targets, independent of orthographic and semantic relatednesss, suggesting that the processing of derived words with the unproductive -mi affix makes recourse to morpheme-level representations.