A Aging is an inevitable component of the maturation process in all living organisms. Arnold B. Scheibel, M.D., a professor at the University of California at Los Angeles, notes that we now have evidence that the brain's deterioration is parallel to that of the aging body. Studies performed with chimpanzees, monkeys, and other lower species have shown that the younger of the species consistently outperform their older counterparts in memory tests. In humans, scientists have concluded that memory and other mental functions deteriorate over time due to organic changes in the brain. This appears inevitable after young adulthood.
B Stanley Rapoport, Ph.D. at the National Institutes of Health, conducted a study using imaging techniques to monitor brain activity in old people and young people. Participants were assigned with the task of matching photos of faces. With the knowledge that blood flow shows neuronal activity, Rapoport was able to discern which neuronal networks were used by the different subjects in matching the face photos. “Even when the reaction ties of older and younger subjects were the same, the neural networks they used were significantly different. The older subjects were using different internal strategies to accomplish the same result in the same amount of time, ”notes Rapoport, meaning that either the task required more effort on the part of the older participants or the neurons originally involved in the task were supplanted by other neurons， thus creating different networks.
C The mind's ability to adjust to deteriorating function is evidenced in a typing study conducted by Timothy Salthouse, Ph.D. a psychologist at the Georgia Institute of Technology. Salthouse took a group of college-age typists and pitted them against a group of typists in their 60s. Salthouse expected the younger typists to be faster, because he knew their reaction was faster, and that the fingers of older people would be less nimble than those of the younger typists. Surprisingly however, both groups were able to type at a similar speed. It seems that the less nimble older counterparts were able to compensate for lack of dexterity by making fewer finger movements, saving typing time, and by reading ahead in the text.
D The effects of stimulation and varied environment were revealed in a study by Marian Diamond, a professor of integrative biology. Using rats as her study subjects, Diamond found that when a rat was isolated from other playmates or objects to interact with, the animal's brain shrank. When the rat was surrounded by 11 other rats in a large cage and given an assortment of wheels, ladders, and other toys, significant differences appeared in the brain. After just 30 days in this enriched environment, the cerebral cortexes and the blood supply of the rats had already expanded noticeably.
E Our memories begin as events, according to Harry Bahrick, Ph.D, from Ohio Wesleyan University. “Through repetition, certain events leave behind a residue of knowledge, or semantic memory,”, he says. For example, sometime in the past, someone told you that two plus two is four. As time passed, you became so familiar with the fact that two plus two equals four that this information became ingrained in your memory and you may no longer remember where you initially got this information. What started as an episode or event has become a permanent part of your knowledge base and although you can easily remember the content, you are not able to remember the context.
F In an effort to determine the longevity of knowledge, Bahrick conducted a study of 1,000 high school graduates of varying ages. Some of the study participants had graduated as recently as a month ago; some of them had completed their courses 50 years ago; all participants had studied algebra, the focus of Bahrick's study. Surprisingly, Bahrick found that a person's algebra acumen at the time of testing didn't have anything to do with when the course was taken. Instead, the major determinant was the duration of the instruction. Participants who spent just a short time learning algebra (i.e. -just a few months) forgot most of it within two or three years.
G Bahrick did a similar study which proves the same point. His study subjects were persons who had taken courses in Spanish. He found that people who had taken multiple courses in Spanish could recall, sometimes decades later, up to 60 percent of the vocabulary they had learned. On the other hand, people who had taken only one course, retained very little of the Spanish they had learned within three years. Bahrick concluded, “This long-term residue of knowledge remains stable over the decades, independent of the age of the person and the age of the memory.”
H As you might expect, any specialized knowledge we accumulate improves with experience. For example, when you apply yourself to a specific interest such as cooking, you will accumulate knowledge regarding cooking as you practice it. Like cooking, vocabulary is an example of an area of accrued knowledge. Retired professionals such as writers and teachers consistently score higher on vocabulary tests than college students who are supposedly at their mental peak.