We always speak of sustainable learning when our brain has processed the information and stored it in long-term memory. During each processing step, links are created between the individual brain cells. The more often we repeat something, the stronger these links become, until the narrow path between the nerve cells has become a “data highway”. And the more new knowledge we acquire, the faster our brain is at creating new connections and the better we learn.
Even seemingly useless knowledge is therefore not useless. Even if we never have to solve an equation again after our school career, we have trained our brain and “learned to learn”. This training helps us when we later want to learn something else that we need, for example, for our job or for a hobby.
By the way: if the brain is not trained, it breaks down like a muscle that is not used. That’s why we should always be open to learning something new, even at an older age, be it a sport, a language or perhaps a musical instrument. Learning is like a fountain of youth that keeps us healthy and independent for longer.