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Aaron P. Johnson, Nicolaas Prins, Frederick A. A. Kingdom, Curtis L. Baker; Ecological validity determines the impact of second-order information on perceptual performance. Journal of Vision 2006;6(6):568. doi: 10.1167/6.6.568.
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The human visual system is sensitive to modulations in the first-order (luminance) and second-order (contrast and texture) information within the natural world. Although there is psychophysical and neurophysiological evidence that first- and second-order information are processed separately by the visual system, the two are strongly correlated within the natural world (Johnson & Baker, 2004). Here we investigated whether first- and second-order information interact in determining perception, and if so whether the interaction is dependent on their spatial correlation. Using micropattern texture stimuli with a sine-wave modulation of element orientation (2–4 cycles/image), subjects performed a 2AFC spatial frequency discrimination task. Micropattern textures were comprised of either first-order only (Gaussians), second-order only (Gabors or contrast-modulated noise), or first- and second-order micropatterns whose spatial correlation was varied from 0% to 100%. Subjects exhibited good performance using only first-order micropatterns, but they could not perform the task in the second-order only condition. However when second-order micropatterns were presented together with first-order information, the results depended on their spatial correlation: task performance was augmented maximally when their spatial correlation was 75% or more, and fell back to levels below first-order only information as correlation declined to anti-correlation conditions (0%). This result suggests that while humans are capable of performing the discrimination task with only first-order information, perceptual performance is augmented by the presence of second-order cues, but only when presented in ecologically valid combinations.
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