This study addresses the issue of prefix processing and representation by taking into account two quantitative dimensions of prefix distribution in Italian: (1) the number of word-types in which a given prefix is present; (2) the quantitative relationship between this number and the number of wordtypes in which the same orthographic sequence is present as a pseudoprefix. The effects of these two variables were evaluated in two lexical decision experiments on printed stimuli. In both the experiments, we assessed the performance of subjects on prefixed nonwords resulting from the illegal combination of a prefix and a real word in Italian. The prefixes included in the nonwords vaned along the two dimensions. The results showed that decision latencies varied according to the values of the second variable (the quantitative relationship between prefixed and pseudoprefixed words in the language), which appeared to be effective in determining the likelihood of prefix recognition with subsequent morphologjcal decomposition of the stimulus. The results are discussed within a model of lexical access in which lexical entries can be addressed through the activation of a morpheme access procedure which is sensitive to the distributional properties of affixes.

In two naming experiments, it was shown that response times for morphologically structured pseudowords are faster than those for orthographically matched controls. These results are consistent with those obtained in lexical decision tasks with morphologically structured pseudowords. The implications of these results for models of lexical processing are considered. In particular, it is argued that the results reported provide support for compositional models of lexical knowledge.