Testable subjects with clear rules are called explicit. They have clear rules and a top down transmission of knowledge from teacher to student. And they are ideally suited to a classroom environment.
The result of this is that they train an area of the mind involved in explicit memory.
This is the famous iceberg analogy used to explain the difference between explicit and implicit. The explicit section of the iceberg (referring to the conscious mind) is the part we can see above water. The submerged part refers to our subconscious mind, the implicit section.
Interestingly enough, many courses that introduce this analogy such as my organizational behavior class continue to teach everything in an explicit fashion, undermining its own legitimacy as a valid course. But I digress.
The importance of this is to understand how implicit learning works. Implicit learning uses different areas of the brain and nervous system involved in creating implicit memory.
Learning occurs in a biological sense through the creation and strengthening of neural pathways called synapses. The synapses create activation-response circuits that we refer to as behavior.
This occurs whether learning is implicit or explicit. In explicit learning, we are conscious of exactly what we have learned and can easily explain it. With implicit it is much more indirect. This leads in people discounting it, or feeling like they haven't "learned anything".
Most physical movement for example relies on implicit learning. It's how even people who have impaired short term memory (such as those who've had head injuries) are able to learn certain things such as new movements, even when they have forgotten the memory of actually learning it. In sports it is often referred to as "muscle memory".
It is not just movement that is learned implicitly. Our emotional reactions are often conditioned in the same way, which is why we will sometimes act a certain way but have difficulty saying why.
Natural language is subject to this same learning, for better and worse. The "illusion as truth effect" experiment referred to in the wikipedia entry above and other research indicates we are primed towards language that is familiar. We are more likely to feel comfortable with it and believe it to be true. It is also why if we want to be happier, we should stop talking so much about our misery and talk more about our potential. And why if we want to get over racism, celebrating diversity is the last thing we should do. We should be talking about the similarities of all people, and not celebrating "racial differences".
As we become older and are run through the modern day education system, we become "educated". "Educated" in this case means to rely on the explicit functions of the mind uniquely. It carries the dogma that explicit learning is superior to implicit.
In reality, explicit learning is more applicable to certain types of learning. Implicit based learning is better for others. Many trades require extensive experience that can only be gained implicitly. Traditionally, Japanese would spend years observing masters of a trade before attempting the skill themselves. This is why we hear about ancient Sushi chefs not even doing more than making balls of rice for years before they start on sushi.
I propose that adults can still learn language this way. There are enough examples of people who have learned languages as adults to a native level for this to be a valid assumption. But as far as I know there hasn't been any major scientific studies of this.
So we get fooled by explicit learning dominated linguists and psychologists who tell us it is not possible to become like a native in a language once we get too old. Most of these people have never experienced learning another language, or have had very limited experience. Almost all of them have only tried explicit language learning methods, and then declared all language learning methods will not work.
To recognize the difference between explicit and implicit is knowledge, but to know which one is best for a situation is wisdom.
