Friday, January 31, 2014

The myth of cognitive decline with aging? Yes and No....

Offering something of an antidote to the drumbeat of articles measuring cognitive declines on again, Ramscar et al. (open source) suggest that changing performance patterns that are typically taken as evidence for (and measures of) cognitive decline arise out of basic principles of learning and emerge naturally in learning models as they acquire more knowledge, with patterns of performance reflect the information-processing costs that must inevitably be incurred as knowledge is acquired. Their arguments seem relevant to lexical tasks such as recalling words, but are not germane to declines in visual or auditory attention and processing speed (usually described as 'cognitive' declines) for which underlying brain structural and functional correlates have been observed. They also do not address the issue of noise, or competition from competing memories, as influencing lexical retrieval tasks. The second abstract below, work of Healey et al., notes this possibility. So, first the Ramscar et al. abstract:
As adults age, their performance on many psychometric tests changes systematically, a finding that is widely taken to reveal that cognitive information-processing capacities decline across adulthood. Contrary to this, we suggest that older adults'; changing performance reflects memory search demands, which escalate as experience grows. A series of simulations show how the performance patterns observed across adulthood emerge naturally in learning models as they acquire knowledge. The simulations correctly identify greater variation in the cognitive performance of older adults, and successfully predict that older adults will show greater sensitivity to fine-grained differences in the properties of test stimuli than younger adults. Our results indicate that older adults'; performance on cognitive tests reflects the predictable consequences of learning on information-processing, and not cognitive decline. We consider the implications of this for our scientific and cultural understanding of aging.
And now the Healey et al. abstract on noise or interference resolution by younger but not older adults:
Resolving interference from competing memories is a critical factor in efficient memory retrieval, and several accounts of cognitive aging suggest that difficulty resolving interference may underlie memory deficits such as those seen in the elderly. Although many researchers have suggested that the ability to suppress competitors is a key factor in resolving interference, the evidence supporting this claim has been the subject of debate. Here, we present a new paradigm and results demonstrating that for younger adults, a single retrieval attempt is sufficient to suppress competitors to below-baseline levels of accessibility even though the competitors are never explicitly presented. The extent to which individual younger adults suppressed competitors predicted their performance on a memory span task. In a second experiment, older adults showed no evidence of suppression, which supports the theory that older adults’ memory deficits are related to impaired suppression.

After I composed the above post Benedict Carey's mention of the Ramscar et al. article appeared in the NYTimes and became a 'most emailed article' for several days. He makes the same points that I do as a counter to over-interpreting Ramscar et al.'s data.


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