Age and the Elderly Internal Clock: Further Evidence for a Fundamentally Slowed CNS

Abstract

Earlier studies have found little or no effect for age on the estimation of time. These results may reflect a true independence, or they may be an artifact of a subvocal counting strategy or an automatic and unconscious recalibration process by the elderly that adjusts for a slowed internal clock. These alternatives were examined by requiring subjects to estimate a prescribed time interval either alone or while also engaged in a resource demanding secondary task. The secondary task was assumed to prevent or inhibit the use of a counting strategy and any such recalibration processes from occurring. Thirty-two subjects, consisting of 16 young (mean age = 25 yrs) and 16 old (mean age = 71 yrs) individuals, performed a time estimation task both alone (unfilled interval production, the single-task condition) and while simultaneously counting backwards by threes from a number between 50 and 100 (filled interval production, the dual-task condition). Results indicated that while no age differences existed in interval production during the single-task condition, the older adults significantly overestimated the 10–sec interval during the dual-task condition, compared to the younger subjects. These findings are interpreted in terms of a slowed internal clock in the elderly. Such a slowing of the internal clock may explain a significant portion of the age-related variance in speed of behavior.