Chromatic Vasarely effect

Vasarely's 'nested-squares' illusion is the perception of a glowing “X” along the diagonals of concentric squares with a luminance gradient. We present here the chromatic Vasarely effect, where the concentric angles have a chromatic gradient, under iso-brightness conditions. The strength of the effect was tested psychophysically by two measures, the length and the color of the illusory folds. The color of the illusory fold is perceived as the complementary color of the color of the nested-squares (or angles). The experimental results show that a large repertoire of stimuli with different colors and angles yielded significantly perceived colors. The results show that the strength of the perceived illusory fold (of both the length and the chroma) is significantly larger at sharper angles of the stimuli. The chromatic first-order adaptation computational model predicts most of the above results.