Small-angle Attraction in the Tilt Illusion PDF Download

Author: Aysegül Akgöz
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Languages : en
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Book Description
"The tilt illusion defines the phenomenon in which a surround or inducer grating of a particular orientation impacts the perceived orientation of a central test grating. Typically, inducer-test orientation differences of 5-40 deg drive the test grating orientation to appear shifted in a direction away from that of the inducer orientation, i.e., show repulsion. The inducer typically causes the test grating orientation to appear shifted towards that of the inducer orientation in the region 60-90 deg, i.e. shows attraction. Both repulsion and attraction effects have been observed in contrast-modulated and luminance-modulated grating patterns. In this thesis, I demonstrate that a secondary, small-angle (0-10 deg) attraction effect is observed in contrast-modulated and orientation-modulated gratings, as well as with luminance-modulated gratings that are relatively low in spatial frequency low in contrast or contain added micropattern texture. The observed small-angle attraction, which in some instances exceeds in magnitude the repulsion and the aforementioned large-angle attraction effects, is dependent on the spatial phase relationship between the inducer and test, being maximal when the center and surround are in in-phase condition. Both small-angle attraction and repulsion effects are reduced when a gap is introduced between test and inducer. My findings suggest that small-angle attraction in the Tilt Illusion is likely a result of the blending or assimilation of the receptive fields of the neurons sensitive to the inducers and tests when those are similar in orientation"--