Exploration of vertical bias in perceptual completion of illusory contours: Threshold measures and response classification

We investigated whether the perceptual completion of illusory contours exhibits a vertical bias (J. Pillow & N. Rubin, 2002). Experiments 1-3 measured completion with Pillow and Rubin's shape discrimination procedure, while including novel control conditions to determine if the results were related to perceptual completion per se. These experiments found no evidence for perceptual completion with stimuli used by Pillow and Rubin but did find …