Enright (1995 Vision Research 36 307 – 312; 1995 Perception 24 Supplement, 32 – 33) described a simple piece of equipment for demonstrating a highly sensitive perceptual mechanism that he called sequential stereopsis. The apparatus prevents ‘conventional’ stereopsis mechanisms from operating as it prevents the comparisons of disparities of targets seen at the same time. Enright suggested that the mechanism of sequential stereopsis relies on a comparison of disparities before and after isovergent saccades between fixations of the two targets. In his apparatus, the observer makes fixations between two textured targets seen behind a pair of viewing ports and the task is to adjust these to appear equidistant. The principle upon which the apparatus depends is the use of textures whose elements cannot be resolved in peripheral vision at the eccentricity determined by the target separation. Enright used a fine sandpaper for this purpose. We describe two similar experiments (N=3 in both) with high-bandpass filtered textures which eliminate any possibility of the low-spatial-frequency content of sandpaper textures playing a role. Our results corroborate Enright's general conclusions on sequential stereopsis while at the same time showing that high-bandpass textures do not give wholly similar results to sandpaper. Possible reasons for this are discussed.
