Memory declines with age, but how much and which type of memory grows dimmer with the years is still being analyzed.

"The evidence of loss of speed and perceptual faculties is real clear for age," says Nobel laureate Herbert Simon. "But the evidence for loss of effective memory except in the case of Alzheimer's disease is not real clear."

With age, animals lose "their capability to store long-term information," says Dr. Eric Kandel, a scientist at Columbia University's College of Physicians and Surgeons in New York. "But they still have perfectly good short-term information."

Where memory doesn't diminish with age, however, is in the use of a mental process called plausible reasoning strategy -- a method humans use to construct answers without doing a detailed search of memory.

Carnegie-Mellon's Lynne Reder found that older people have difficulty with direct memory retrieval but do well in plausible reasoning.

Consider, for example, the film "Star Wars." Remembering that the cloaked character in the dark mask was named Darth Vader would use direct memory retrieval. But recalling that Darth Vader represented evil would employ plausible reasoning strategy.

Even if older people do experience some memory loss, memory training can help, suggests a study published last year in the American Journal of Psychiatry. Stanford University Medical School's Dr. Jerome Yesavage found that "training programs for normal elderly individuals have been shown to improve" selected thinking processes, including memory, "to about the same degree that some of these processes decline with aging."