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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jml.2009.01.003 Byline: M.A. Ford (a), M.H. Davis (b), W.D. Marslen-Wilson (b) Keywords: Morphology; Lexical representation; Frequency effects; Lexical decision Abstract: Morpheme frequency effects for derived words (e.g. an influence of the frequency of the base 'dark' on responses to 'darkness') have been interpreted as evidence of morphemic representation. However, it has been suggested that most derived words would not show these effects if family size (a type frequency count claimed to reflect semantic relationships between whole forms) were controlled. This study used visual lexical decision experiments with correlational designs to compare the influences of base morpheme frequency and family size on response times to derived words in English and to test for interactions of these variables with suffix productivity. Multiple regression showed that base morpheme frequency and family size were independent predictors of response times to derived words. Base morpheme frequency facilitated responses but only to productively suffixed derived words, whereas family size facilitated responses irrespective of productivity. This suggests that base morpheme frequency effects are independent of morpheme family size, depend on suffix productivity and indicate that productively suffixed words are represented as morphemes. Author Affiliation: (a) Center for Speech and Language, Department of Experimental Psychology, University of Cambridge, Cambridge CB2 3EB, UK (b) MRC Cognition and Brain Sciences Unit, Cambridge, UK Article History: Received 9 January 2007; Revised 1 December 2008

A technique for studying the relationship between brain and language, which involves correlating scores on two continuous variables, signal intensity across the entire brains of brain-damaged patients and behavioral priming scores, was used to investigate a central issue in cognitive neuroscience: Are the components of the neural language system organized as a single undifferentiated process, or do they respond differentially to different types of linguistic structure? Differences in lexical structure, in the form of the regular and irregular past tense, have proven to be critical in this debate by contrasting a highly predictable rule-like process (e.g., jump-jumped) with an unpredictable idiosyncratic process typified by the irregulars (e.g., think-thought). The key issue raised by these contrasts is whether processing regular and irregular past tense forms differentially engages different aspects of the neural language system or whether they are processed within a single system that distinguishes between them purely on the basis of phonological and semantic differences. The correlational analyses provide clear evidence for a functional differentiation between different brain regions associated with the processing of lexical form, meaning, and morphological structure. morphology | neuroscience