What is a word? Recognizing polymorphemic lexical items in DLI.

This paper addresses issues of frequency and transparency in word recognition and their importance for the organization of the mental lexicon in Developmentally Language Impaired (DLI) francophones. A simple visual lexical decision task probes responses of DLI and control participants when presented with verbs. DLI participants are sensitive to whole-word frequency and show little or no transparency effects. These results are interpreted as indicating that words are not organized according to "morphological families" in the DLI mental lexicon, but rather according to a principle of frequency. These facts support the hypothesis that words in the DLI mental lexicon lack lexical features and morphological structure.