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General Slowing Hypothesis

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Abstract

Age-related slowing of responses to cognitive tasks is a ubiquitous phenomenon in research on cognitive aging. The general slowing hypothesis is built upon broad observations in many studies of age-related slowing and suggests that age-related general slowing is the primary contributor to the declines in cognitive functioning associated with aging. This entry provides a brief overview of the general slowing hypothesis and its research background, the evolution of models and debates, and cognitive training research based on the hypothesis.

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... Alternatively, these age differences could reflect true age effects. The general slowing hypothesis (Choi and Feng 2015) attributes age-related declines in literacy during adulthood to a general loss in mental capacities that is due to biological ageing processes. In line with this idea, recent longitudinal findings suggested that age-related declines in reasoning (fluid intelligence) and perceptual speed are responsible for literacy losses among older adults ). ...
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We combined data from six studies, all using the same speed of processing training program, to examine the mechanisms of training gain and the impact of training on cognitive and everyday abilities of older adults. Results indicated that training produces immediate improvements across all subtests of the Useful Field of View test, particularly for older adults with initial speed of processing deficits. Age and education had little to no impact on training gain. Participants maintained benefits of training for at least 2 years, which translated to improvements in everyday abilities, including efficient performance of instrumental activities of daily living and safer driving performance.
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IntroductionAge-Related Cognitive Slowing as a PhenomenonAge-Related Cognitive Slowing as an Explanatory ConstructIntraindividual VariabilityThe Diffusion ModelExplanatory Models for Cognitive SlowingPlasticity of Processing SpeedConcluding RemarksReferences
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We evaluated the debates concerning brinley plots and the associated theories of age-related slowing. We concluded that an explicit debate regarding a single-factor, general slowing model was no longer a debate as most, if not all, agree to the disconfirmation of that model. We address sources of confusion in the debates that have muddled the areas of genuine disagreement. When the confusion is lifted, the remaining debate centers, rightly, on evaluation of theories of aging. We show that Brinley plot analyses can lead to both falsely accepting and falsely rejecting theories of agerelated slowing. Although plotting data most certainly can assist with the evaluation of cognitive theory, we argue that models of performance and learning must play a more central role in advancing theories of cognitive aging
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Research into the effects of aging on response time has focused on Brinley plots. Brinley plots are constructed by plotting mean response times for older subjects against those for young subjects for a set of experimental conditions. The typical result is a straight line with a slope greater than 1 and a negative intercept. This linear function has been interpreted as showing that aging leads to a general slowing of cognitive processes. In this article, we show that the slope of the Brinley plot is actually a measure of the relative standard deviations of older versus young subjects' response times; it is not a measure of general slowing. We examine current models of the effects of aging on mean response time and show how they might be reinterpreted. We also show how a more comprehensive model, Ratcliff's diffusion model (1978), can account for Brinley plot regularities and, at the same time, provide an account of accuracy rates, the shapes of response time distributions, and the relative speeds of error and correct response times, aspects of the data about which models designed to account for Brinley plots are mute. We conclude by endorsing a research approach that applies explicit models to response time data in aging in order to use the parameters of the model to interpret the effects of aging.
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