What kind of noise increases with age?

It was hypothesized that internal representations of visually presented stimuli are noisier because of higher random neural activity or less precise relations among neuronal units in the central nervous systems (CNSs) of older persons than in younger persons. The rationale for and results from manipulations designed to examine predictions derived from this hypothesis are discussed. Age-related differences in an incomplete picture-identification task were found to be similar to those resulting from the addition of random background noise in stimulus displays of young adults.