This well-known saying is not even true of dogs; ( add link) and in humans, studies show that older people are frequently more highly motivated and persistent than their younger counterparts in training courses. (add link)
When mixed age groups learn together, not only can older people be better students but their presence frequently motivates younger people to try harder. Older students and trainees make good use of their life experience in helping them deal with new situations and can rely on their greater understanding of people.
There is a related belief that ageing slows the brain. It is true that ageing can create cognitive changes, however there is evidence that this varies in different areas of intelligence; older people may have slower reaction times, but “mental capabilities that depend most heavily on accumulated experience and knowledge, like settling disputes and enlarging one’s vocabulary, clearly get better over time,” writes Patricia Cohen in the New York Times. And the brain’s neuroplasticity continues as long as it is exercised (link) – the old adage “use it or lose it” may be a more useful approach