Age differences in dark-interval threshold across the life-span.

The threshold for the dark interval between two flashes was used to examine differences in stimulus persistence in 72 subjects aged 20 to 79 years. The data were then combined with results from two previous studies involving children and adolescents; thus, a cross sectional, adult, life-span view of differences in the dark-interval threshold was presented. Results showed that during childhood and adolescence there is a decline in stimulus persistence as a result of decreased receptor sensitivity. In adulthood, however, the dark-interval threshold remains fairly stable until the 70s where it increases significantly. Two possible explanations for this increase in stimulus persistence in old age are discussed.