On the locus of age differences in visual information processing

Age differences in visual information processing were investigated in a study of monoptic backward masking. Young (18 to 22) and old (58 to 73) adults were tested in three experiments utilizing both a random visual noise and a pattern (fragments) mask, with two-letter combinations serving as target stimuli. Critical target duration needed to escape masking was measured at several mask durations in Exps. 1 and 2; critical interstimulus interval was assessed at several target durations in Exp. 3. With random noise as the mask, a small but reliable age difference was seen across the range of mask or target durations, supporting previous reports of age differences in peripheral processing. With the pattern mask as the masking stimulus, there was mixed evidence for age differences in central processing. Such age effects were clearest in Exp. 3 in which the role of luminance summation had been reduced. Control procedures in Exps. 1 and 2 tended to eliminate evidence for central masking. Results are discussed in terms of the magnitude of age differences in peripheral and central processing and in terms of procedural artifacts of previous research.