Date of Award

Fall 1987

Project Type

Dissertation

Program or Major

Psychology

Degree Name

Doctor of Philosophy

Abstract

Two lexical decision experiments were performed to investigate the lateralization of the word frequency effect and the interaction with word class. Positive results would support proposals of multiple lexicons in lexical retrieval models. The first was a small-n experiment varying visual angle of presentation, signal to noise ratios, visual field and word class (noun/verb) while using high frequency word and nonword items. The purpose of this experiment was to document the sensitivity of observers to material presented varying distances from a central fixation point while replicating previous research results of a word class by visual field interaction. The second experiment was a large-n design varying visual field, word class (noun/verb/mixed), and word frequency, looking for greater differences in lateralization of word class by frequency. Results of the first experiment show no visual field by word class interaction, failing to replicate previous research. Speed of response slowed linearly with increasing visual angle of presentation for both visual fields, despite moving away from a region of macular overlap to parafoveal presentation. In experiment two, a strong frequency effect was found, along with an interaction with word class and visual field. This interaction, however, was due to aberrant performance for medium frequency nouns. Considered along with the inconclusive literature on lateral effects of word class and word frequency, and recent failures to replicate Bradley's (1978) model of open- and closed-class lexicons, the research focus must shift toward a closer examination of the relationship between two areas: (1) the method of generation of a lexical access code (which may or may not involve the RH) and, (2) the relationship between a rapidly calculated direct access code and an ordered lexicon.

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