This statement is true.
A critical period is an early postnatal time when the development of brain properties is very dependent on outside stimuli.
If the organism does not receive the necessary stimuli during that time, some life skills may not developed or their development may be severely delayed.
There are different critical periods for different brain functions, for example binocular vision or language acquisition. A first language may not be easy to learn later in life if the critical period for learning it is somehow missed.
In sports, the critical period has proven that the earlier you start an activity, the better you become at mastering it. It is almost impossible to master a new sport after the age of 20.
