The Effects of Aging on Semantic and Phonological Processing During Lexical Access

Normal aging has been shown to impact cognitive processes, including those necessary for lexical access. While there is previous research on semantic and lexical processing during lexical access, there is a limited body of research investigating how healthy aging impacts these processes specifically. The aim of this thesis project was to provide further insight into age-related changes in lexical access and compare these patterns to predictions made by two major theories of aging, the Inhibition Deficit Hypothesis (Hasher et al., 1991; Hasher & Zacks, 1988) and the Transmission Deficit Hypothesis (Burke et al., 1991; MacKay & Burke, 1990), to understand why age-related changes in processes required for lexical access may occur. The Visual World Paradigm was used to measure age-related changes in semantic and phonological processes. A group of 9 younger participants and 1 older participant completed a Visual World Paradigm (Cooper, 1974) task in which they heard a word and had to select the corresponding image on the computer. Trials consisted of a 4x4 grid with a target word (e.g., lime), a phonological competitor (e.g., lion), a semantic competitor (e.g., grapefruit), and an unrelated distractor (e.g., rock). Using an eye-tracker, data on the total time spent gazing at each competitor type was collected, analyzed, and compared descriptively between groups to understand semantic and phonologic activation patterns across the lifespan. Further statistically analysis was conducted on data from the younger participants to determine statistical significance of age-related changes in lexical access. Results from this thesis project suggest that younger adults experience similar amounts of activation across competitor types while older adults experience greater semantic activation than phonological activation. Given that the age-related changes in lexical processing experienced by older adults is likely asymmetrical, findings were most consistent with predictions made by the Transmission Deficit Hypothesis