A new kind of stereoscopic vision

A vertical grating of different spatial frequency in the two eyes mimicks the views gained of a real grating rotated about its vertical axis. This is exactly the sensation that such a binocular stimulus produces. The impression of rotation is complete and global: the whole grating seems fused until the difference in spatial period exceeds about 30 per cent. At low (below 0.6 c/deg) and high (above 15 c/deg) spatial frequencies the phenomenon does not occur. The break in fusion comes at the same ratio of periods whatever the angular width of the gratings. The sensation is not affected by movement or a slight reduction in contrast of the grating in one eye. This kind of stereopsis may be dependent upon a comparison of the spatial periodicity of the patterns in the two eyes, rather than a point-by-point analysis of positional disparity. There may, in fact, be binocular neurones with different optimal spatial frequencies in the two eyes. © 1970.