The effects of amplitude-spectrum statistics on foveal
and peripheral discrimination of changes in natural images,
and a multi-resolution model
C.A. Parraga a,*, T. Troscianko a, D.J. Tolhurst b

a Department of Experimental Psychology, University of Bristol, 8 Woodland Road, Bristol, BS8 1TN, UK
b Department of Physiology, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
Received 18 November 2004; received in revised form 29 July 2005

Abstract

Psychophysical thresholds were measured for discriminating small changes in spatial features of naturalistic scenes (morph sequences), for foveal and peripheral vision, and under M-scaling. Sensitivity was greatest for scenes with near natural Fourier amplitude slope, perhaps implying that human vision is optimised for natural scene statistics. A low-level model calculated differences in local contrast between pairs of images within a few spatial frequency channels with bandwidth like neurons in V1. The model was ‘‘customised’’ to each observers contrast sensitivity function for sinusoidal gratings, and it could replicate the ‘‘U-shaped’’ relationships between discrimination threshold and spectral slope, and many differences between picture sets and observers. A single-channel model and an ideal-observer analysis both failed to capture the U-shape.

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