Intelligence and skill comes in many forms. Fine and coarse motor skills are one example. Our ability to move our body is a mixture on mental and physical abilities. Training mind and body is fundamental to martial arts, as well as many other physical activities.
Neuroscientists are still researching both fundamental question about how our brains work, to say nothing of the fine details. But we do have some understanding of the neurons and electrical charges that occur in our heads. Repeating a physical action, training for a martial art move, causes a certain pattern to occur in our head. Each repeat of the move causes the same pattern pathway to be followed. The more you repeat the technique the easier it is for the pathways in your mind to repeat the pattern.
Behaviourist scientists have observed similar phenomena for years without mentioning the brain. Behaviour is reinforced through repetition. It can become automatic, a reflex that does not require conscious decisions. This is almost common sense.
An advantage of this repletion and practice is that it affects performance under pressure. If we have only made moderate progress with a technique we tend to have a compromised performance when under exam conditions or suffering any stress. But the opposite happens when we become really advanced. When sufficiently proficient our ability becomes optimal in stressful situations. Given that martial arts are most needed in stressful situation, competitions or self-defence, this training is a priority. Martial art training aims to develop instinctive reactions that are there when we most need them.
Taekwondo training for self-defence or competition can teach us how to handle stress and the adrenalin rush of a legitimate threat. It is more than practiced techniques; it is psychological preparation for conflict.