Age differences in central perceptual processing: a dichoptic backward masking investigation.

Age differences in central perceptual processing were investigated using young (mean age 19.5 years) and old (mean age 64.2 years) subjects in a backward masking paradigm known to produce central interference. Subjects were presented with symmetrical, straight-lined letters as target stimuli (TS). The masking stimulus (MS) was a pattern of line segments of the same width as the strokes of the letters spaced evenly over the part of the visual field occupied by the letters. The TS was presented to the right eye and followed by the MS to the left eye. A robust masking effect was found for both young and old across conditions in which TS energy was much greater than MS energy. The asynchrony between TS and MS onset (SOA) was found to be the variable describing escape from masking for both age groups. However, the older group required 24% longer SOAs than the young to escape masking, suggesting a slowing with age in central perceptual processing.