Here is a great example of why we need to interpret our results carefully, not just jump to the conclusion that a correlation demonstrates a cause/effect relationship.
In this study, they found that the reason it takes older people longer to do many cognitive tasks is that they have so much information in long term memory that is simply takes longer to search through it. And/or they have more partially correct answers to discard before getting to the best one. So instead of a cognitive decline in aging, it is actually that older people are more knowledgeable. This has implications not just for our understanding of aging, but also how we design user experiences for the aging user.
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.