The eldest participants did just as well on the tests as the youngest did. And yet the MRI scans indicated that the elders' left frontal and temporal lobes and certain visual centers, which together are responsible for language recognition and interpretation, were much less active. The researchers did find that the older people had more activity in brain regions responsible for attentiveness, such as the posterior cingulate cortex. Darren Gitelman, who headed the study, concluded that older brains solved the problems just as effectively but by different means.

Similar adaptation seems to aid memory, too. In 2003 Mara Mather and her colleagues at the University of California at Santa Cruz found that older adults who performed well on memory tests used a process of comparing bits of memories that was different from the memory-recollection mechanisms used by younger men and women.

The reason aging brains can forge new capabilities that compensate for certain declines is that neuronal networks are surprisingly flexible, or "plastic." They can adapt. Animal experiments prove that an intact nerve cell can take over the function of a neighboring nerve cell that has become damaged or that has simply withered with time. The brain creates ways to keep itself sharp by making these kinds of adjustments on a widespread scale over time.

Although researchers still know little about how to help the brain adapt to overcome the declines associated with aging, they do know that exercise--physical and mental--can provide some benefit. A rising number of studies have noted that senior citizens who stay more physically active have less deterioration in the brain than those who are sedentary [see "Smart Exercise," by Aimee Cunningham; Scientific American Mind, Vol. 16, No. 1; 2005].

Even more studies show that people who continue to challenge themselves intellectually have lesser rates of Alzheimer's disease and other forms of dementia and mental decline. Neurologists who have conducted such work recommend that people continue to engage in everything from crossword puzzles and book clubs to college courses and political debate. They can take up a musical instrument. Or learn a new language like Rita did. Not only will these vocations keep aging minds sharp, they will give their owners a sense of satisfaction in their never-ending mental powers.

This article was originally published with the title Experience versus Speed.

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