Age-Related Differences in Thematic and Taxonomic Semantic Processing

Over the lifespan, cognitive abilities are subject to change and decline. While there is a general slowing of cognitive processing with age (Mather, 2010), certain functions are disproportionately impacted by aging over others. Language function follows the variable pattern of age-related change noted above. Certain language functions are well-maintained throughout the lifespan, while others are not (Shafto & Tyler, 2014). The present study was motivated by the cognitive and linguistic changes that accompany aging to investigate differences in lexical access between younger and older adults. Specifically, the current study investigated differences in semantic (i.e., meaning-based) similarly using eye-gaze measures. Two types of semantic relationships were investigated: taxonomic (i.e., shared features or categories) and thematic (i.e., co-occurrence in scenes) relationships. Following the Regression Hypothesis, we predicted specific interference from thematic competitors for older adults based on an increased preference towards thematic thinking across the lifespan (Belacchi & Artuso, 2018; Maintenant et al., 2011; Smiley & Brown, 1979). We also expected that older adults may experience a general increase in semantic competition, for both taxonomic and thematic semantic competitors, consistent with the Inhibitory Deficit Hypothesis (Hasher et al., 1999). Nine younger and one older adult participated in the study. Data was collected using the Visual World Paradigm (VWP). Participants viewed four images on a screen while hearing a word and were instructed to select the image that corresponded to the spoken word presented. Participants were presented with an image of the target word, a phonological competitor, a semantic competitor (either thematically or taxonomically related to the target word), and an unrelated distractor. Cumulative gazes to each type of competitor were used as a dependent measure. Results showed that there were no significant difference in gazes to either taxonomic or thematic semantic competitors. Descriptive statistics for the older adult revealed more gazes to the thematic than the taxonomic semantic competitor. These results are consistent in part with the Regression Hypothesis but are inconsistent with the Inhibitory Deficit Hypothesis. This study provides preliminary findings regarding age-related changes in semantic processing; however, future work should expand upon and validate the findings reported here