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The manner in which the spatial characteristics of simple discrimination tasks change with time after the onset of a stimulus were examined. The experiments measured the improvements in sensitivity to the length, orientation, curvature, and stereoscopic depth of short lines that accrue with increased exposure durations. These improvements can be(More)
MIRAGE, a theory for the primitive coding of the (1D) spatial distribution of luminance changes by the human visual system is developed from a theoretical examination of the practical problems associated with the characterization of such changes. The main novel feature of the theory is that the multiplicity of spatial filters in human vision is assumed to(More)
Experiments are reported that measure the precision with which observers can (a) discern the degree of blur of an edge, (b) distinguish between two different types of blur, and relate the locations of two such edges by judging their (c) misalignment or (d) separation. Three blurring functions were used, and detailed examination of the retinal stimulus in(More)
Vernier acuity demonstrates a fine sense of relative visual location, which can be exploited to examine the question of mechanisms for the extraction of position information. By determining the appearance and location of composite stimuli consisting of a number of unresolved parallel bars of different luminances, we have demonstrated that vernier acuities(More)
Relative location acuities similar to vernier acuity were measured for a variety of different luminance profiles and contrasts. The results are interpreted in terms of the extraction of zero-bounded centroids in the responses of a limited range of bandpass spatial filters, with centre frequencies between 3.5 and 30 c/deg. The process by which the outputs of(More)
Curvature discrimination thresholds were measured for a wide range of stimulus curvatures and sizes. Results are compared with an ideal processor of curvature to provide relative efficiencies. The results lead to three major findings. (i) Curved lines may be processed with the same precision as straight lines for decisions of shape, demonstrating a new(More)
Anisometropic amblyopes were found to have a reduced sensitivity for shape discrimination. The introduction of positional jitter in the elements of the display had a profound effect on the performance of the normal eye, but not on that of the amblyopic eye. On the other hand the introduction of gaussian blur affects the performance of both eyes to the same(More)
A wide range of pattern acuity measurements are presented, and detailed comparisons are made between different acuities for different stimuli and tasks. The most striking finding is that only a small number of cues and mechanisms are involved, and there are thus considerable inhomogeneities in spatial perception, even under focused attention and foveal(More)