Age-related differences in two stages of central perceptual processes: the effects of short duration targets and criterion differences.

Two experiments investigated age differences in speed of central perceptual processes using a dichoptic backward masking paradigm. Twelve young (mean age = 19.6 years) and 12 old (mean age = 68.5 years) adults served as subjects. Exp. 1 examined age differences in speed of central perceptual processes using an ascending limits procedure and forced-choice responding to control for criterion differences. Target durations from 2 to 30 msec were used to further test the fit of young and elderly masking functions to the additive rule believed to describe masking which arises centrally (Turvey, 1973). Results from Exp. 1 showed a 33% slower speed of processing in the elderly sample. Furthermore, masking functions for both age groups fit the central rule across the wide range of target durations used. Exp. 2 examined the perceptual detectability of a 2- and 20-msec target at 7 stimulus onset asynchronies between target and masking stimuli using a forced-choice procedure. Subanalysis of two different components of the observed masking functions suggested the elderly sample was equally slow in completing both an early and late stage of central perceptual processing.