An investigation of pre-motor encoding for production of high and low frequency words
Calkins, Camilla Leilani, 1973-
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Theories of spoken language production propose that the formulation of an utterance entails processing at a number of functionally distinct stages. The stages of processing that include the generation or retrieval of an abstract phonologic representation (i.e., lexeme), and motor programming, and that occur prior to motor execution are collectively referred to as pre-motor encoding.The dual route model for pre-motor encoding proposes that processing within these stages proceeds by means of two distinct routes: an indirect route, through which the phonologic representation of a word is created by means of the assembly of sublexical units, and a direct route, in which the phonologic representation of a word is retrieved as a whole unit, precluding the need for sublexical assembly.According to the dual route model, the route through which a word is processed depends upon the frequency with which the word is used. Thus the dual route model accounts for the word frequency effect, the robust finding that high frequency words are responded to faster than low frequency words, by ascribing fundamentally different mechanisms for the pre-motor encoding of high frequency versus low frequency words. A central tenet of the dual route model, then, is the assumption that the word frequency effect arises during the stages of pre-motor encoding---the lexeme-as-locus hypothesis.Experiment 1 tested the lexeme-as-locus hypothesis using the cross-modal picture-word interference paradigm, an online method of investigating response preparation. It was hypothesized that greater phonologic interference effects would be obtained for low frequency words than for high frequency words.Counter to the prediction, however, greater interference effects were obtained for high frequency words. This unexpected result led to the formulation of a new hypothesis relative to the dual route model, the interference-induced assembly hypothesis.Experiment 2 tested this hypothesis using a variation of the cross-modal picture-word interference paradigm, which involved reading words rather than naming pictures. Null results were obtained. However, trends in the data provide some support for both the dual route and the interference-induced assembly hypotheses. These trends and their implications for further investigation of the interference-induced assembly hypothesis are discussed.
- Speech