Human speech is a closed-loop system

Human speech is a complex learned skill and is dependent on a number of memory and neurological functions. Speech is a closed-loop system because sensors within the system itself give feedback to the control portion of the system.

The control then corrects and coordinates ongoing speech. In this case, the mind is in control of the closed-loop system, the mouth produces the desired product (speech), and auditory feedback from the ears and feedback from the nerve sensors in the mouth allow the mind to coordinate the speech process in real time.

When you speak your own language, your mind stores all of the vocabulary you need. Your mind also controls your tongue, mouth, and breathing. Your hearing is also an important part of the control because your ears hear everything your mouth says.

Therefore, what you say next is partially dependent on the vocabulary and other information stored in your mind. But what you say next is also dependent on what your ears are hearing your mouth say, and on the feedback that is coming from the nerves in your tongue and mouth.

Because you have spoken your own language all of your life, all of this control is automatic—you do not need to think about it. But when you learn to speak English, you must retrain all of these processes so that they will all work together at the same time.

It is not enough to simply put new vocabulary words or grammar drills into your memory. You must retrain your mind to use all of the new sounds your ears will hear, as well as the new movements of your tongue, mouth, and breathing. Yet, since all of these things must happen together for you to speak fluent English, all retraining of your memory, hearing, and the nerves in your mouth must be done simultaneously.