ABSTRACT
With a large number of receptive channels, the human visual system processes information in a parallel fashion. A single glimpse acquires a wealth of information; the eld of view for two eyes is 180° horizontally and 120° vertically (Mehr and Shindell, 1990). e spatial resolution in the central (foveal) part of the visual eld is approximately 0.5-1.0 min of arc (Shlaer, 1937), although Vernier acuity, the specialized task of detecting a misalignment of two lines placed end to end, is much ner, approximately 2 s of arc (Stigmar, 1970). Low-contrast presentations substantially reduce visual acuity.
