The corner Poggendorff.
With the classic Poggendorff illusion a set of parallel 'induction lines' will cause a set of oblique line segments to look misaligned even though they are collinear. A different kind of misalignment can be produced by placing the induction lines so that they form a corner. Under these conditions the obliques will appear to be angled slightly, one relative to the other. The effects are small, but can be seen and reliably reported by a group of naive subjects. The influence of the induction lines drops sharply as their relative position is moved from parallel to orthogonal, but there is a small residual influence which may be called the corner Poggendorff effect.
Greene
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Department of Psychology, University of Southern California, Los Angeles 90089.
D001288:Attention; D004193:Discrimination Learning; D005556:Form Perception; D006801:Humans; D007088:Illusions; D009903:Optical Illusions; D009949:Orientation; D010364:Pattern Recognition, Visual