CONFIGURAL EFFECTS CONSTRAIN FOURIER MODELS OF PATTERN-DISCRIMINATION

Many models of spatial pattern discrimination assume that judgments are based on information directly available from mechanisms tuned to limited ranges of spatial frequency and orientation. We tested the validity of this assumption for spatial frequency, orientation, and contrast information in a series of complex pattern discrimination experiments. Observers discriminated between simple gratings, between gratings masked by components that differed widely in spatial frequency and/or orientation, and between patterns that presented two cues to discrimination, one in each frequency and/or orientation band. Component cues were combined either in rigid-object correspondence (e.g. both components were rotated clockwise in one pattern and counterclockwise in the other) or in opposition (e.g. in one pattern one component was rotated clockwise, the other counterclockwise; the direction of rotation was reversed for each component in the second pattern). The results demonstrate that information from tuned pathways is not always used directly in making spatial judgments, but in some cases is combined across wide regions of the Fourier domain prior to the discrimination decision. We find two distinct patterns of combination that appear to independently signal information about texture and edges. These findings provide a potential link between low-level, spatially tuned analyzers in the visual system and higher-level pattern processing mechanisms.