Pictorial depth and the Poggendorff illusion.
An informal demonstration is offered, which strongly supports previous contentions that, when the elements of a Poggendorff display appear to be arranged in pictorial space such that the two critical line segments are at different heights, an illusory impression of misalignment may occur. A second pair of demonstrations shows, however, that such a height difference is neither a necessary nor a sufficient cause of the illusion. In addition, the harmful effect of adding certain pictorial elements to the standard Poggendorff pattern requires a new understanding.
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D001288:Attention; D003867:Depth Perception; D005556:Form Perception; D006801:Humans; D007088:Illusions; D009903:Optical Illusions; D009949:Orientation; D010364:Pattern Recognition, Visual