Several competing theories of cognitive aging have attempted to account for factors that may plausibly mediate the relationship between age and cognitive functioning. The proposed study evaluated two leading theories of cognitive aging: Lindenberger and Baltes’ Sensory Theory and Salthouse’s Processing Speed Theory, through novel means. Instead of solely focusing on intergroup comparisons, the current study examined older adults spanning four decades using a short-term, within-session intraindividual variability design. The relation between intraindividual variability on cognitive and sensory variables and mean level of performance on verbal and nonverbal assessments of memory was examined. Moreover, this study examined whether intraindividual variability on cognitive measures was related to selfreported negative affect. In the present investigation, we examined 102 healthy adults ranging from 45-89 years of age using a short-term, within-session intraindividual variability design. Participants were administered repeated assessments of processing speed and sensorimotor tasks and single assessments of verbal and non-verbal memory tests. Self-report questionnaires assessing subjective memory and sensory function as well as affect were also administered. Consistent with the current literature, we found that both processing speed and sensorimotor function accounted for significant age-related variance in memory performance, though processing speed appeared to be a stronger mediator. Contrary to findings from other studies, we failed to find an association between intraindividual variability on measures of processing speed/sensorimotor function and memory performance. Moreover, unlike other studies, we did not identify a link between intraindividual variability and self-reported affect.