Cross-sectionally and Longitudinally Balanced Effects of Processing Speed on Intellectual Abilities (original) (raw)
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Aging, cognitive performance, and mental speed
Intelligence, 1992
Measures of four-choice reaction time (RT), inspection time (IT), and scores on a speeded coding-substitution task obtained from 104 subjects aged from 54 to 85 years were found, separately or together, to account for almost all age-related changes in cognitive performance on a number of performance indices reflecting general fluid ability. However, measures of information-processing speed did not entirely predict some aspects of memory performance. These correlations were not due to the inclusion of persons who had lower than average IQ scores or who were over 80 years old, or to the fact that some psychometric tests were scored to a time limit. The results also showed that higher intelligence does not serve to protect against the effects of aging, because rates of decline with age in scores on tests of spatial ability, and in memory and in information-processing tasks were the same within two subgroups selected for higher and lower verbal crystallized abilities.
Speed and intelligence in old age.
Psychology and Aging, 1993
Past research suggests that age differences in measures of cognitive speed contribute to differences in intellectual functioning between young and old adults. To investigate whether speed also predicts age-related differences in intellectual performance beyond age 70 years, tests indicating 5 intellectual abilities--speed, reasoning, memory, knowledge, and fluency--were administered to a close-to-representative, age-stratified sample of old and very old adults. Age trends of all 5 abilities were well described by a negative linear function. The speed-mediated effect of age fully explained the relationship between age and both the common and the specific variance of the other 4 abilities. Results offer strong support for the speed hypothesis of old age cognitive decline but need to be qualified by further research on the reasons underlying age differences in measures of speed.
Scandinavian Journal of Psychology, 2008
The processing speed account suggests that general slowing of mental processing speed results in an overall decline, especially age-related decline, in other cognitive domains. Support for the speed account comes mainly from cross-sectional studies with participants that vary in age (age-heterogeneous samples). This study investigated how well variations in processing speed predict change of episodic recall in a longitudinal framework and examined with the Narrow Age Cohort (NAC) design. Data were obtained from Betula, a population-based longitudinal study. Both 5-year (n= 490; Time 3 - Time 4) and 10-year follow-up results (n= 608; Time 1 - Time 3) were used. In both samples, which were subjected to prospective dementia screening, we found considerably weaker associations in longitudinal data compared to cross-sectional, and also weaker associations in age-homogeneous than in age-heterogeneous samples. The results provide little support for the speed account.
Intelligence, 2012
Many aspects of cognition decline from middle to late adulthood, but the dimensionality and generality of this decline have rarely been examined. We analyzed 20-year longitudinal data of 6203 middle-aged to very old adults from Greater Manchester and Newcastle-upon-Tyne, UK. Participants were assessed up to eight times on 20 tasks of fluid intelligence, perceptual speed, memory, and vocabulary. We controlled for potential effects due to retest, city, sex, and socio-economic class. Average performance in all tasks declined with age, and individual differences in decline were present for all but one memory and two vocabulary tasks. Half of the variance in level of performance was shared across tasks. This proportion increased to 66% for individual differences in change. General level of performance and change therein correlated positively. We conclude that cognitive decline is heterogeneous across individuals and rather general at the within-individual level.
Processing speed, working memory and reasoning ability from childhood to old age
Personality and Individual Differences, 2010
The study investigated whether theoretical causative relations among declining cognitive abilities during adulthood and old age conform to a literal reversal of improving cognitive development during childhood. Children aged 8-14 years (n = 240) and adults aged 18-87 (n = 238) completed the same battery of psychometric tests, which defined latent traits for processing speed, working memory, and reasoning ability. Speeded performance improved during childhood and slowed across the adult range. Childhood performance was well described by a developmental cascade, whereby increasing chronological age is accompanied by faster processing speed, which influences improved working memory, which in turn influences improving reasoning ability. However, although adult performance resembled a cascade with diminishing reasoning ability mediated by processing speed and working memory, this was not a mirror image of the cascade for children. The main difference with adults was a direct causal path between age and working memory. Post hoc analysis located this among adults aged 55 years and over. This suggests that, whereas childhood cognitive development is substantially mediated by processing speed, declining reasoning ability in old age is influenced by slower processing speed but also by age-related change(s) influencing working memory that are independent from processing speed.
Longitudinal mediation of processing speed on age-related change in memory and fluid intelligence
Psychology and Aging, 2013
Age-related decline in processing speed has long been considered a key driver of cognitive aging. While the majority of empirical evidence for the processing speed hypothesis has been obtained from analyses of between-person age differences, longitudinal studies provide a direct test of within-person change. Using recent developments in longitudinal mediation analysis, we examine the speed-mediation hypothesis at both the within-and between-person levels in two longitudinal studies, Longitudinal Aging Study Amsterdam (LASA) and Origins of Variance in the Oldest-Old (OCTO-Twin). We found significant within-person indirect effects of change in age, such that increasing age was related to lower speed, which in turn relates to lower performance across repeated measures on other cognitive outcomes. Although between-person indirect effects were also significant in LASA, they were not in OCTO-Twin which is not unexpected given the age homogeneous nature of the OCTO-Twin data. A more in-depth examination through measures of effect size suggests that, for the LASA study, the within-person indirect effects were small and between-person indirect effects were consistently larger. These differing magnitudes of direct and indirect effects across levels demonstrate the importance of separating between-and within-person effects in evaluating theoretical models of age-related change.
Cognitive Processing Speed across the Lifespan: Beyond the Influence of Motor Speed
Frontiers in Aging Neuroscience
Traditional neuropsychological measurement of cognitive processing speed with tasks such as the Symbol Search and Coding subsets of the WAIS-IV, consistently show decline with advancing age. This is potentially problematic with populations where deficits in motor performance are expected, i.e., in aging or stroke populations. Thus, the aim of the current study was to explore the contribution of hand motor speed to traditional paper-and-pencil measures of processing speed and to a simple computer-customized non-motor perception decision task, the Inspection Time (IT) task. Participants were 67 young university students aged between 18 and 29 (59 females), and 40 older adults aged between 40 and 81 (31 females) primarily with a similar education profile. As expected, results indicated that age group differences were highly significant on the motor dexterity, Symbol Search and Coding tasks. However, no significant differences or correlations were seen between age groups and the simple visual perception IT task. Furthermore, controlling for motor dexterity did not remove significant age-group differences on the paper-and-pencil measures. This demonstrates that although much of past research into cognitive decline with age is confounded by use of motor reaction times as the operational measure, significant age differences in cognitive processing also exist on more complex tasks. The implications of the results are crucial in the realm of aging research, and caution against the use of traditional WAIS tasks with a clinical population where motor speed may be compromised, as in stroke.
Psychology and Aging, 1997
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Speed of information processing and age
Personality and Individual Differences, 1991
Young adults and adults who were 60yr or older were compared on measures of general intelligence. inspection time. reaction time and responding time. The intelligence test used was the Ravens Progressive Matrices and the inspection time. reaction time and responding time measures were calculated from a two choice reaction time task. Inspection time was determined by varying the duration of exposure of a stimulus prior to the onset of a mask consisting of both stimuli. Inspection time was measured as the shortest sttmulus duration at which a subject could identify a stimulus with near perfect accuracy. Responding time was then measured by setting the stimulus duration at each subject's individual inspection time and then reducing the time available to make a response prior to the onset of the next stimulus. Responding time was calculated as the shortest duration of the interval between the end of a stimulus and the onset of the next stimulus at which a subject could respond with near perfect accuracy. Reaction time was measured from the onset of the stimulus to the pressing of the response key in the respondrng ttme task. Two additional measures. termed response initiation time and checking and preparation time were calculated by subtracting inspection time from reaction time and response initiation time from responding time respectively. The old subjects were found to have lower intelligence test scores. longer inspectton times and longer checkmg and preparation times but not longer reaction times or response initiation times. These results suggest that age increases the time taken to input information correctly and to cheek the accuracy of the previous response and prepare for the next stimulus but that it has less elTcct on the time taken to initiate a response after correction identification of the stimulus.