CORBIS, OWAKI/KULLA
Only 40 years ago it was widely believed that if you lived long enough, you would eventually experience serious cognitive decline, particularly with respect to memory. The implication was that achieving an advanced age was effectively equivalent to becoming senile—a word that implies mental defects or illness. As a graduate student back then, I was curious why such conclusions were being drawn about the elderly. I had only to look as far as my own great-grandmother and great-aunt to begin questioning the generalization. They lived to 102 and 93, respectively, and were exceptionally active and quick-witted enough to keep us twentysomethings on our toes. A closer look at the literature didn’t give me any confidence that either the biological basis of memory or how it ...