RELATIONSHIP BETWEEN SPATIAL INTEGRATION AND SPATIAL SPREAD OF CONTRAST ENERGY IN DETECTION

Detection efficiencies were measured for two kinds of grating stimuli. The stimuli of the first kind were uniform square shaped cosine gratings of various sizes but of constant spatial frequency. The stimuli of the second kind were composed of nine small grating patches of the same spatial frequency arranged into a square array. The array size was varied by changing the inter-patch distance. The efficiencies for the two kinds of stimuli obeyed the same decreasing function of area defined by the respective outlines of the grating patch array and the uniform grating. The result means that detection efficiency is not determined by the retinal area stimulated, but by the distances between different parts of stimulus, i.e. the spatial spread of contrast energy, which can be described by a radial moment measure computed from the image.