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Enrico Giora, Simone Gori; Visual competition between ambiguous and unambiguous motion signals in grating patterns. Journal of Vision 2008;8(6):122. doi: 10.1167/8.6.122.
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A rigid square-wave grating is illusorily perceived as a deforming latex stuff when observed in dynamic viewing. Observers refer an orthogonal expansion to the bands and a shrinking distortion throughout the grating when moving the head either towards or away from the pattern. We call that phenomenon “Accordion Grating”. The reported orthogonal-to-the-bands expansion cannot be trivially depending upon the reduction of the viewing distance. Furthermore, afterimage could not account for the perceived deformation affecting only the dimension orthogonal to the grating bands. According to Gori and Yazdanbakhsh (in press), that illusory effect can be instead understood by considering the competition between motion signals (Gurnsey et al., 2002) originating from two different motion-processing units (Lorenceau et al., 1993). Thus, ambiguous signal from contour units would compete with veridical motion cue from line terminator units. If the contour units will win the competition the illusory effect will be perceived. Confirming that hypothesis, the illusory effect is drastically reduced when using bands composed by small rectangles, which minimise the activity of the contour units, or with a grating arranged as concentric circles pattern. Finally, the illusory effect disappears by using iso-luminant colours. That suggests the involvement of the magno-cellular pathway in the phenomenon.
Gori, S., ∓ Yazdanbakhsh, A. (in press). Perception.
Gurnsey, R., Sally, S. L., Potechin, C., & Mancini, S. (2002). Perception 31, 1275-1280.
Lorenceau, J., Shiffrar, M., Wells, N., & Castet, E. (1993). Vision Research 33, 1207-1280.
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