Discrimination of natural scenes in central and peripheral vision.

We conducted suprathreshold discrimination experiments to compare how natural-scene information is processed in central and peripheral vision (16° eccentricity). Observers' ratings of the perceived magnitude of changes in naturalistic scenes were lower for peripheral than for foveal viewing, and peripheral orientation changes were rated less than peripheral colour changes. A V1-based Visual Difference Predictor model of the magnitudes of perceived foveal change was adapted to match the sinusoidal grating sensitivities of peripheral vision, but it could not explain why the ratings for changes in peripheral stimuli were so reduced. Perceived magnitude ratings for peripheral stimuli were further reduced by simultaneous presentation of flanking patches of naturalistic images, a phenomenon that could not be replicated foveally, even after M-scaling the foveal stimuli to reduce their size and the distances from the flankers. The effects of the peripheral flankers are very reminiscent of crowding phenomena demonstrated with letters or Gabor patches.