The perceived speeds of gratings with various spatial frequencies, which shifted at the same speed, were evaluated using psychophysical methods. When the gratings shifted at low speeds, perceived speeds were found to be independent of the variation in the spatial frequencies of the gratings. However, at high speeds, an increase in spatial frequency was found to result in an increase in perceived speed. Furthermore, secondary polynomials were found to represent the relations between perceived speed and spatial frequency more accurately than the linear expressions claimed previously by other researchers.
