Abstract
Four-stroke apparent motion (FSAM) is a phenomenon in which the repetition of a four-image sequence creates the illusion wherein an object in the sequence is moving in a single direction. Usually, the illusion is produced by playing two consecutive frames followed by two frames with the negative and positive sides of luminance polarity reversed (Anstis & Rogers, 1986; Kawabe et al. 2019). On the other hand, methods to generate image sequences that can induce FSAM through image optimization have not been investigated. In this study, we propose a method to generate images inducing FSAM by image optimization based on the motion energy model (e.g., Adelson & Bergen, 1985). In particular, using the model of V1 complex cells that output motion energy from two images in the first and second images, we optimized the third and fourth images so that the motion energy between the second and third images, the third and fourth images, and the fourth and first images was equalized to the motion energy between the given first and second images. The outcome of the optimization procedure contained the negative-positive reversed version of the first and second images, and FSAM was observed by repeatedly playing back the sequence with original and optimized image pairs.