The Pulfrich pendulum phenomenon in stereoblind subjects.
The Pulfrich pendulum phenomenon, in which a pendulum swinging in the frontoparallel plane appears to swing in an ellipse when a neutral density filter is placed over one eye of the observer, was investigated in stereoblind subjects. It was found that such subjects can report the presence of the Pulfrich effect although they fail to fuse random-dot stereograms and fail to exhibit interocular transfer of the movement aftereffect. These findings suggest that 'stereoblind' subjects must retain some residual binocular mechanism for depth perception. Three possibilities are considered: (i) the stereoblind may be able to utilise contiguous temporal disparities as a cue for depth in the Pulfrich effect; (ii) they may retain some residual binocularity, sufficient to reveal the Pulfrich effect but not for other more demanding tasks for the binocular mechanisms; and (iii) they may retain some coarse magnocellular pathway disparity mechanism having lost their high-acuity parvocellular disparity system. There is little evidence to support any of these hypotheses, but the third shows promise.
Thompson
P
P
Department of Psychology, University of York, UK.
Wood
V
V
D003867:Depth Perception; D004292:Dominance, Cerebral; D005260:Female; D005403:Fixation, Ocular; D006801:Humans; D008297:Male; D013236:Stereognosis; D015357:Vision Disparity; D014796:Visual Perception