Though also subject to opinion, I also find the rapid development of children to not only be biological, but spiritual. We are taught that the Holy Ghost is the teacher of all truth. Therefore, of course when our teachers in 2nd grade taught us that 2+2=4, the Holy Ghost would confirm the truthfulness of that logic. I believe the Holy Ghost can confirm many of those same sorts of topics. However, the difference with children is their spiritual purity. The Holy Ghost has no trouble filling the hearts and souls of those beautiful pure and innocent children so much so that it may testify at will and the child will receive the witness just as the messenger delivered it. How I wish that I could be as a child and remain so pure that the Holy Ghost could speak to me so! This example shows how the spiritual development and biological development of a human can cooperate through life periods.
Prepared with an active mind and full of eagerness for new experiences, the young adult mind is primed for instructions from the Lord. A college student is looking for their place, their mark, their opportunity to make history. What a great time for the Lord to send forth his specific calls to His children so that they might properly prepare themselves for the world to come. How those calls come or how to know that the Lord has spoken to you in such a manner I wish I knew. Being a college student myself, I can't say I've had personal experience enough yet to know what the whole stage is like. What I do know though is that my heart is open and my spirit willing.
I would not be surprised if the Lord has prepared the development of our persons to fit the biological/spiritual patterns necessary to make our lives completely in sync. I am anxious to see in my future life how my biological preparation prepares me for spiritual callings. One such stage that comes to mind is the wisdom associated with the older generations. Such wisdom must be well developed for callings prepared by the Lord for those He can trust to lead and perform great works. I personally would feel much more comfortable speaking with an experienced and learned Bishop than one that was not. I thank the Lord for His careful preparation and design for this wonderful existence. I know I can trust Him completely.