RECOGNITION OF BAND-PASS FILTERED HAND-WRITTEN NUMERALS IN FOVEAL ANDPERIPHERAL-VISION

The purpose of the present study was to find out what differences betw een foveal and peripheral pattern recognition remain unexplained by th e inhomogeneities of retinal sampling and the optics of the eye. We me asured contrast thresholds for pattern recognition at different eccent ricities. The effects of retinal sampling were homogenised by using M- scaling of the stimuli, and the effects of the optics of the eye were by-passed either by using strong external noise (signal-to-noise ratio is not affected by optical attenuation) or by computing retinal image contrast by means of the optical modulation transfer function. The st imuli were hand-written numerals filtered to two-octave bands of vario us centre object spatial frequencies (c/object). The results were desc ribed as contrast thresholds and recognition efficiency. At all eccent ricities, lowest contrast thresholds and highest recognition efficienc ies were found at medium object spatial fr,frequencies. At high object spatial frequencies the peripheral retinal contrast thresholds and re cognition efficiencies were nearly as good as at the fovea, but at low object spatial frequencies most of the data showed superiority of the fovea to the periphery. Therefore, at high object spatial frequencies peripheral recognition performance could be explained relatively well by the retinal sampling gradient, or equivalently by the cortical mag nification factor, together with the effects of the optics of the eye. Some eccentricity dependent deterioration of recognition at low objec t spatial frequencies remained unexplained. (C) 1998 Elsevier Science Ltd. All rights reserved.