Critical Period

In developmental biology and psychology, a critical period is a maturational stage in an organism's lifespan during which its nervous system is especially sensitive to particular environmental stimuli, such that if the organism does not receive the appropriate stimulus during that window, the associated skill or trait may become difficult, less successful, or even impossible to develop later in life. Functions indispensable to survival, such as vision, are particularly likely to develop during a critical period, and the concept has also been applied to a person's ability to acquire their first language, with people who pass the window without developing communication skills failing to become fluent later. Researchers distinguish strong critical periods from more extended weak or sensitive periods after which learning remains possible, though some consider the two the same phenomenon; the critical period for a human infant's binocular vision, for example, is thought to run from about three to eight months, with sensitivity to disruption extending to at least three years of age.