Some plane truths about pictures: notes on Wagemans, Lamote, and van Gool (1997).
Wagemans, Lamote, and van Gool (1997) have attempted to show that observers can determine the geometric equivalence of shapes seen in perspective, or in projective transformation. Artifacts of measurement in their procedures forestall such a conclusion. Their experiment fails to control projective properties adequately, and also confounds the transformations of shear and compression. Their evidence that observers can discern the equivalence of shapes under perspective can be reconstrued as evidence for sensitivity to different, unrelated properties: to the plane compression that follows from the depiction of flat shapes in perspective, and to gross differences in shape not specific to projective geometry. An improved set of procedures is proposed for the measurement of stimuli in the study of visual shape constancy.
Niall
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Simulator Technologies Group, Defence and Civil Institute of Environmental Medicine, Toronto, Ontario, Canada.
D016477:Artifacts; D006801:Humans; D010364:Pattern Recognition, Visual / Q000502:physiology*; D015203:Reproducibility of Results; D014787:Vision Tests