A new random-dot stereo illusion and its application to the Anstis-Howard-Rogers effect.
When the dynamic visual noise of an untuned television set is viewed with image defocusing (positive lenses) and with a narrow vertical obstruction partially blocking the pupil of one eye, the video 'snow' seems to separate into two stable surfaces at different depths, divided by a vertical discontinuity. The main features of this illusion can be quantitatively accounted for in terms of the optics of defocused images and the retinal disparities predicted from blur circles. A residual component of the illusion, however, which was perceived by a majority of subjects, cannot be readily explained by geometrical optics; it apparently reflects a more subtle aspect in the processing of visual images, corresponding to the Anstis-Howard-Rogers stereo-effect, in which local depth configurations can bias global stereopsis. Several novel aspects of that effect are described, based on use of this obstructed-pupil illusion as the evoking stimulus.
D000328:Adult; D000368:Aged; D003867:Depth Perception / Q000502:physiology; D006801:Humans; D007088:Illusions / Q000502:physiology; D008875:Middle Aged; D009903:Optical Illusions / Q000502:physiology; D011305:Presbyopia / Q000503:physiopathology; D011680:Pupil / Q000502:physiology; D012160:Retina / Q000502:physiology