Figure 4.

Experiment 1 results: (a) mean Likert ratings for amount of motion observed for 9.44 reversals per second flickering Cornsweet, unipolar Gaussian, and solid-line circles. At the group level, Cornsweet circles were perceived to have a greater illusion strength than either other stimulus type. It should be further noted that in spite of the lack of a significant difference in the perceived illusion strengths for the Gaussian and solid-line conditions, of the individual participants, only four produced an average illusion strength score that was higher for Gaussian circles than the solid-line stimuli. (b) Mean amount of motion observed in each condition in terms of real motion calculated using the log fit of real motion and Likert ratings for nonflickering Cornsweet circles. Error bars represent standard error.