Electronic Thesis and Dissertation Repository


Master of Science




Dr. Jody Culham


We examined the effect of familiar size of objects on size perception. Participants matched the size of a target image to the perceived size of a central image in the Ebbinghaus illusion. The central image was identical throughout all trials (a 25-mm-wide dog), but the annuli varied in physical size (12 mm vs. 37 mm), semantic category (animate vs. inanimate), and familiar real-world size (cat vs. horse for the animate category; shoe vs. car for the inanimate category). Importantly, the familiar size relationship between the center and the annuli was either congruent (e.g., dog surrounded by small shoes or large cars) or incongruent (e.g., dog surrounded by large shoes or small cars). The illusion was smaller in the congruent conditions than the incongruent conditions for the inanimate category. These results show that perceived size is affected by familiar size relationships.