Across a range of psychometric tests, reaction times slow as adult age increases. These changes have been widely taken to show that cognitive-processing capacities decline across the lifespan. Contrary to this, we suggest that slower responses are not a sign of processing deficits, but instead reflect a growing search problem, which escalates as learning increases the amount of information in memory. A series of computational simulations show how age-related slowing emerges naturally in

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... models, as a result of the statistical properties of human experience and the increased information-processing load that a lifetime of learning inevitably brings. Once the cost of processing this extra information is controlled for, findings taken to indicate declines in cognitive capacity support little more than the unsurprising idea that choosing between or recalling items becomes more difficult as their numbers increase. We review the implications of this for scientific and cultural understanding of aging.