This is called the critical period.
The critical period itself is a stage of the development in the life of a human being in which is said that skills are most easily and most readily learned and acquired. This period usually varies for different things like binocular vision and language, but it is said that after the critical period the skills are acquired with much difficulty if they are to be acquired at all.
The thyroid gland is partially obscured by the Sternocleidomastoid. I hope this helps:)
It's because it helps you know about areas that not not native to you and helps you understand others people home land