Abstract
Speed of visual information processing alters as we age. Using a visual backward masking (VBM) task, we have compared cohorts of various ages (10, 15, 20, 40 and 60 years of age) on three parameters of a two-stage model (Lagged-Accrual Model, LAM) presented by Muise, LeBlanc, Lavoie and Arsenault, 1991. Of particular interest were the duration (Tlag) of initial chance performance reflecting sensory transduction and transmission, the rate (theta) of central information accrual and level (alpha) of asymptotic performance. These parameters were shown to vary systematically as a function of age, similarity of stimulus set (CGOQ vs IOSX) and stimulus intensity (0.57, 0.70, 0.86, and 1.06 cd/m2). Surprisingly, speed of sensory processing was already at its fastest for the 10 year-olds. The rate of extraction was at a maximum at 15 years with a sharp deline for older subjects. Older subjects were less able to take advantage of enhanced information available in increased stimulus intensities and dissimilarities. Differential asymptotic performance in the youngest group as a function of intensity suggests attentional lapses. Results will also be presented that suggest increasing stimulus intensity may “normalize” parametric VBM performance as a function of age. Older subjects may simply need more intense or high contrast stimuli. A discussion follows that may be pertinent to the comparison of different clinical populations in early visual information processing within the context of VBM.