Understanding and Memory Complement Each Other
The brain can hardly form a firm memory of something it does not understand, and at the same time it can hardly form a thorough understanding of something it knows nothing about. Learning is therefore a gradual process; in the early stage of acquiring new knowledge, we can only have a superficial understanding and a fragile memory.
If, after we finish learning, we make an effort to memorize the key points, and then study the material a second time, our understanding will be much deeper. After understanding advances one step further, when we memorize again, the speed of memory will be much faster. Moreover, this round of memorization will help us form chains of knowledge, systematically imprinting the scattered points into our mind.
This is still not enough. After gaining somewhat deeper understanding and memory, we need to study the material once more. This third round will further deepen our understanding, and may even let us strike many sparks of thought, enabling us to discover and raise questions. In this state, memorizing again will be even more effective.
If a course is very difficult and hard to grasp, even three passes are not enough; we need to study repeatedly and memorize repeatedly, thinking while learning and memorizing, digging out new questions, and continually repeating the above process. Only such study can make us an expert in a field; this is especially necessary for university-level and above courses.
My son studies mathematics. He says there is a saying in their major: "Real-variable functions are studied ten times; complex-variable functions are studied over and over." In mathematics, real-variable and complex-variable functions are very difficult, so they must be studied repeatedly. Not only mathematics, but knowledge of other disciplines likewise requires such repeated study to be mastered thoroughly.
If we wish to achieve something breakthrough, we must stand on the shoulders of predecessors and receive basic scientific training; this requires us to be good at learning. Human science has evolved to the present day and formed many mature systems; it is hard to make new discoveries without deep study. No matter how high one's IQ, one cannot grasp profound and complex professional knowledge in a single pass.
Learning follows certain laws, and there are indeed some small tricks that improve learning efficiency. But in the final analysis, what learning most needs is interest and a hard investment of time. We often say that interest is the best teacher; those interested in learning will seek out ways to learn on their own. Interest also allows a person to study without tiring; it helps us screen out all manner of outside temptations and immerse ourselves in our own world. The foundation of focus is interest. Without the drive of interest, autonomous deep learning is hard to come by; without autonomous deep learning, innovation is out of the question. If learning stays superficial, not only can it not be mastered, but it is easily forgotten completely soon after. But once one enters a state of deep learning, things are very different.
The study of medicine places great emphasis on memory. Medicine has developed to the point where basic medical knowledge is already very rich, and this part must be firmly memorized. To study medicine well, one must repeatedly cycle through deepening understanding and strengthening memory until the material is letter-perfect. Even if AI can one day replace human doctors in storing information, if we have memorized too few points of knowledge, we will lack the very ability to distinguish and select the information AI provides, making it hard to put medical AI to good use.