Temporal aspects of binocular slant perception

We investigate temporal aspects of binocular slant perception in the presence and absence of a visual reference. Subjects judge slant induced by large-field stereograms of which one half-image is either horizontally scaled or sheared relative to the other half-image. Each stimulus is presented for different observation periods ranging from 0.1 to 19.2 sec. We quantitatively corroborate earlier findings that perceived slant develops significantly faster and to higher levels with visual reference than without it. In daily life, when we are active, there will not be much time for slant to develop. We find that if observation periods are brief (a few seconds or less) slant is poorly perceived if there is no visual reference. We conclude that the visual system is relatively insensitive to large-field horizontal scale and shear.