Focused learning is looking at a problem set and trying real hard to get it. Diffused learning is just letting your mind wander without a plan. It’s important to deepen your understanding and trigger creative thoughts. Both are important. To maximise your overall learning outcome, play ping pong between the two: focus, relax, focus, relax, focus, relax,…
In practice, that means first focus with all your attention ideally shutting off any distractions (phones, noise,...). After doing this for a while (a timer can be useful) deliberately stop to focus and let your mind freely wander around. It’s then when the brain connects what you just focused on with other information stored in your memory. That process leads to deeper thinking, better retention and allows to for creative thoughts to happen.
Painter Salvador Dali and inventor Thomas Edison both actively worked with it. After a round of focused work, Dali sat on his armchair to think and doze off. In one hand he held a big key and the moment he fell asleep the key dropped, which woke him up and so he went back to the canvas to continue his focused work. Steve Jobs broke up his daily thinking routine by going out for long walks.
Even in tests, the technique can be useful. Start with the most difficult problem first, once you get stuck, switch to a more simple one. While doing the easier one, your brain will keep the difficult problem in its working memory and without you even realizing it is looking for connections to make sense of it. Once you are done with the easy problem, go back to the difficult one. You might find it not as hard anymore.
The technique is based on material from the MOOC Learning How to Learn by Barbara Oakley, PhD, PE, is a professor of engineering at Oakland University in Rochester, Michigan.