Metacontrast masking with texture-defined second-order stimuli

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★ Texture-defined second-order stimuli yield monotonic type A metacontrast effects. ★ These same stimuli also yield nonmonotonic (U-shaped/type B) metacontrast effects. ★ Variations in surface feature contrast of these stimuli do not impact metacontrast. ★ Metacontrast can operate beyond level of first-order stimulus processing.

We examine metacontrast masking with texture-defined second-order stimuli. Our results reveal that (1) the monotonic type A as well as the nonmonotonic (U-shaped) type B metacontrast effect, which has been extensively examined with first-order luminance-defined stimuli, can be obtained with texture-defined second-order stimuli; and (2) while variations of luminance contrast are known to affect the magnitude of metacontrast with first-order stimuli, neither the size nor orientation contrast between texture elements defining the second-order stimuli have a significant impact on the magnitude or shape of metacontrast. These findings bear on theories of metacontrast masking by showing that the mechanism giving rise to nonmonotonic masking effects can operate beyond the level of first-order stimulus processing.

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