Visual phenomena without low spatial frequencies: a closer look

Two studies in which visual grouping and visual illusions were claimed to occur in the absence of low-spatial-frequency information are analyzed in detail. It is shown that this claim was not justified given the characteristics of the stimuli that were used in the demonstrations. It is concluded that visual grouping of unconnected elements without low spatial frequencies cannot be studied, and more work should be done before the role of low spatial frequencies in producing visual illusions is ruled out.