Name: Reba Koenen

Ph.D. Dissertation Defense Meeting

Date: Monday, December 2, 2024

Time: 3:20 pm

Location: Virtual (https://gatech.zoom.us/j/8441938294?pwd=RHcxZm92RmpVZFdaN0xKeVpwMUNLdz09)

Dissertation Chair/Advisor:

Sashank Varma, Ph.D. (Georgia Tech)

Dissertation Committee Members:

Meghan J. Babcock, Ph.D. (Georgia Tech)

Dobromir Rahnev, Ph.D. (Georgia Tech)

Rick P. Thomas, Ph.D. (Georgia Tech)

Jamie C. Gorman, Ph.D. (Arizona State University)

Title: A Modified SpAM Task for Investigating Typicality and Frequency Effects during Category Processing 

Abstract: This dissertation used three tasks to investigate categorization measures and the strength of category norms. Category norms are rank orderings of the most common exemplars (i.e., apple) of a category (i.e., Fruits). Both cognitive psychologists and cognitive scientists have studied how people engage in category processing. The most common method is the production task (with frequency data), followed by the rating task (with typicality data). A third task is the spatial arrangement method (SpAM) (with position data). In the current study, young adult participants (N = 90) completed these three tasks with three experimental categories (i.e., Birds, Fruits, Vegetables), to address three overarching research goals. The first goal was to investigate whether frequency and typicality are comparable indices of the centrality of exemplars to categories. Some correlations between these two measures were larger (r > .39) than predicted. The second goal was to examine the usefulness of a modified SpAM task, its position measure, and a novel measure of placement-order. There were smaller (r < .30) correlations with this data, and both frequency and typicality, than expected. The third goal was to test the novel hypothesis that frequency and typicality effects emerge at different time points during category processing. Placement-order timing correlated best with the frequency and typicality data from the current study, compared to prior studies. Where the evidence in the current study did not support the hypotheses, there are several possible explanations. This may have been a consequence of this study’s novel design (completing all three categorization tasks within-subjects has not been done in prior studies) or a result of the small number of experimental categories (i.e., three). Though these design decisions had their limitations, they also allowed a direct comparison of the three categorization tasks. There was a significant difference in participants’ ratings of how well the different tasks captured their category structures, with participants ranking the rating task as more representative than the production task. The modified SpAM task also had higher category structure representation ratings than the production task, though this difference did not reach statistical significance. These findings should guide future studies of categorization as they suggest there are limitations to the default production task despite its efficiency.