Affixal salience and the processing of derivational morphology: The role of suffix allomorphy

This study explores the relevance of suffix allomorphy for processing complex words. The question is whether structural invariance of the morphological category (i.e., lack of allomorphy) would affect the processing of Finnish derived words. A series of four visual lexical decision experiments in which alternatively surface and base frequency was manipulated showed that the two invariant suffixes, namely denominal –stO and deadjectival –hkO, showed reliable effects of base frequency, whereas for the two categories with suffix allomorphy, deverbal –Us and deadjectival –(U)Us, only surface frequency played a role. A further experiment showed that even with the most frequent variant of –(U)Us, namely –Ude-, response latencies were a function of surface frequency only. It is shown that neither the results from the experiments here nor previous findings from processing Finnish words can be accounted for by suffix frequency, the frequency ratio between the derived word and its base, or morphological productivity in any straightforward manner. We conclude that the lack of allomorphy, that is, structural invariance, significantly adds to affixal salience and therefore enhances morphological decomposition. The implications of this finding for models of lexical processing are discussed