The amount of space you put in between lessons is often as important as the lessons themselves. This applies to both learning as well as teaching.

Let's paint the following scenario:

You'd like to learn a new concept, but the concept actually consists of three different parts, which we'll call A, B, and C. Let's also assume that to understand concept C, you first need to understand concept B, and to understand concept B, you first need to understand concept A. Thus, the dependency structure of the three concepts would look like this:

A -> B -> C

It goes without saying that you should learn A before B and B before C. (A corollary of this is that a teacher should make sure to teach A before B and B before C, but that's the subject of another blog post.) But let's pose the following question:

Is it better to:

1. Learn A, B, and C in one day?

2. Learn A, B, and C on three consecutive days?

3. It makes no difference.

Many scientific studies* have researched the effects of sleep on memory, cognition, and comprehension, and they all indicate that the mind needs sleep to digest the previous day's lessons and process them so that the learnings and memories of each day are properly integrated into the brain.

We'd like to posit that regarding our scenario, it would be best to study A, B, and C on three separate days. Since concept B depends upon concept A, it would be best to first sleep on concept A so that this foundational concept is properly baked into one's mind before tackling a new concept that depends on it. And this isn't to say that you don't truly understand a concept when you first learn it, but there are levels of neural integration that are beyond simple comprehension. That is, the more time your brain has to sit on a concept, the more your mind is used to thinking along the "thought pathways" that the new concept involves. And the more your mind is used to thinking along the new thought pathways, the more the concept will become part of your intuition.

As an example, recall the first time you learned to ride a bicycle. After a number of valiant falls and bruised knees, things finally began to click and you were able to ride for long stretches without falling. However, you still had to consciously think about pedaling and maintaining your balance for some time afterwards. Only after further time did the process begin to become intuitive and did you eventually reach a point where you don't have to pay attention to what you're doing anymore, as your body knows what to do automatically.

Similarly, by sleeping on Concept A, you allow the concept to not just be understood, but to become intuitive, and closer to becoming automatic to your brain. Once Concept A is intuitive (or closer to being so), you have a very solid foundation for tackling Concept B.

Using our bicycle example once again, you're unlikely to be able to ride a bike with no hands if riding a bike generally has not become automatic to your brain yet. Once you no longer have to think about riding a bike in order to do so, you can apply your mind to new tricks such as riding without hands or doing wheelies.

What also follows from this is that a teacher needs to carefully plan lessons so that they follow this structure as well. Just because there's enough time in the day to teach concepts A, B, and C doesn't mean that one should. Students might be better off with being taught concept A and be let out early for the day, so that they can sleep on it before learning concept B on the following day. Switching to a new subject might be a more realistic approach than letting class out early, but the amount of new knowledge that people can absorb in a single day even across multiple subjects is also limited and greatly aided by sleep and time.

* Here are some examples:.