This book looks at lower level visual processing, emphasizing psychophysical experiments which measure the detection and identification of near-threshold patterns and the mathematical models used to draw inferences from experimental results. Neurophysiological and psychophysical evidence is compared and contrasted, while introductory material on psychophysical methods, signal detection theory, and the mathematics of Fourier analysis ensure that the title is accessible to anyone interested in this field. Also included are lists of studies about analysers and parametric sensitivity on various pattern-vision dimensions.