Critical period

A critical period is a period of time in a person's life when they are especially sensitive to certain kinds of things. During this time, it is easier to learn certain kinds of things and it can be harder to change the way you think once the period is over. For example, if you learn a language as a child, it will usually be easier to learn than if you try to learn it as an adult - that's because the critical period for language learning is when you are a child.