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Cabeza recruited a sample group of adults 65 to 95 years old who had scored high on a memory test, along with a group of lower-performing adults of the same age and a group of younger, college-age adults. He then asked them all to perform a series of tasks that called on numerous skills, including language, memory, perception and motor functions. Throughout the tasks, he conducted functional magnetic resonance imaging scans of their brains. Again and again, he found that the high-functioning older adults were using either a hemisphere different from the one the other subjects were using or both hemispheres at the same time.
Why that is so is still unclear, but Cabeza doesn't believe the brain is programmed to get stronger as it ages. Rather, he acknowledges, in many ways it gets weaker, with neurons processing information less efficiently. The bilateralization may be a trick the brain uses to compensate for the decline, sometimes integrating the hemispheres so efficiently that our thought and reasoning processes are actually better than they were before.
"It's similar to the way you need both hands to lift a weight that you could lift with one hand when you were younger," Cabeza says. "In the brain, there's a nice, natural distribution of resources. You get more neural tissue to support the task."
As the brain's flexibility improves, so too may the temperament we bring to our work. There's no question that personalities can calcify with age, causing us to become less receptive to new experiences and flat-out crabby when faced with them. But that's not the case with everyone. In fact, in many people the opposite happens.
In 1958 psychologist Ravenna Helson, now an emeritus professor at the University of California, Berkeley, began a long-term study of 142 women, all of them 21 years old, at Mills College in Oakland, Calif. She interviewed the subjects and took measures of their personalities, drives, relationship skills and the like. Then she reinterviewed them at ages 27, 43, 52 and 61 to determine how those traits changed over time. Just last year she and a graduate student, psychologist Christopher Soto, collated the data from the 123 women who stuck with the study. The results were surprising.
On the whole, they found, the women's highest scores in inductive reasoning occurred from their 40s to their early 60s. Similarly, their so-called affect optimization (the ability to highlight the better aspects of one's personality and restrain the less attractive ones) and their affect complexity (the ability to evaluate various contradictory ideas and remain objective) did not peak until their 50s or 60s. There was also an increased tolerance for ambiguity and an improved ability to manage relationships.
The Mills sample group was hardly random, consisting principally of white women of the same age who attended the same college. Still, they were 123 different individuals, and the results were nonetheless uniform. "People generally describe personality change in middle age as a midlife crisis, with all its negative connotations," says Soto. "In the Mills women, the change was positive--a reorienting, not a crisis."