Roger A. Dixon

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Age differences in three basic types of variability were examined: variability between persons (diversity), variability within persons across tasks (dispersion), and variability within persons across time (inconsistency). Measures of variability were based on latency performance from four measures of reaction time (RT) performed by a total of 99 younger(More)
OBJECTIVE Do lifestyle activities buffer normal aging-related declines in cognitive performance? The emerging literature will benefit from theoretically broader measurement of both lifestyle activities and cognitive performance, and longer-term longitudinal designs complemented with dynamic statistical analyses. We examine the temporal ordering of changes(More)
In young adults, intentions have been shown to be more accessible (e.g. faster reaction times and higher accuracy) compared to other sorts of to-be-remembered information, a result termed an ‘intention superiority effect’ (Goschke & Kuhl, 1993). In the current study, we assessed whether older adults also demonstrate this superiority of intention-related(More)
Data from the Victoria Longitudinal Study were used to examine the 6-year longitudinal stability of personality in older adults. Personality was measured with the NEO Personality Inventory. The longitudinal sample consisted of 223 adults initially ranging from 55 to 85 years of age. Longitudinal confirmatory factor analyses were used to examine the(More)
Little is known about potential longitudinal relationships between participation in social, physical, and intellectual activities and later cognitive performance. Data from the Victoria Longitudinal Study (n = 530) were used to test whether baseline and change in lifestyle engagement were related to corresponding indicators of cognitive speed (measured by(More)
Although the relationship between education and cognitive status is well-known, evidence regarding whether education moderates the trajectory of cognitive change in late life is conflicting. Early studies suggested that higher levels of education attenuate cognitive decline. More recent studies using improved longitudinal methods have not found that(More)
A well-known challenge for research in the cognitive neuropsychology of aging is to distinguish between the deficits and changes associated with normal aging and those indicative of early cognitive impairment. In a series of 2 studies, the authors explored whether 2 neurocognitive markers, speed (mean level) and inconsistency (intraindividual variability),(More)
BACKGROUND Although recent cross-sectional findings indicate that markers of biological age (BA) mediate chronological age (CA) differences in cognitive performance, little is known about their influence on actual cognitive changes. OBJECTIVE The purpose of this investigation is to examine CA and BA as predictors of 12-year cognitive change in a(More)
Performance variability across repeated task administrations may be an important indicator of age-related cognitive functioning. In the present investigation, the authors examined whether age differences and change in inconsistency were related to 6-year (3 occasion) cognitive change. Inconsistency scores were computed from 4 reaction time tasks performed(More)
Confirmatory factor analysis was used to test competing models of declarative memory. Data from middle-aged participants provided support for a model comprised of 2 2nd-order (episodic and semantic memory) and 4 1st-order (recall, recognition, fluency, and knowledge) factors. Extending this model across young-old and old-old participants established support(More)