Skip to main content

Verified by Psychology Today

What Every Parent Needs to Know About Critical Periods

When does the brain get wired? Myths and realities.

These days, many parents panic about whether or not they are doing everything possible to insure that their child will realize their intellectual potential. After all, everyone “knows” that a baby’s brain must be wired by her third birthday—or else the child is doomed to going through the rest of his or her life with a less than optimal brain!

This panic started more two decades ago when brain scientists discovered that the basic brain pathways for seeing and hearing—and the other senses—are laid down in the first three years of life. And they also found that a baby’s developing brain could be modified using neural plasticity in response to certain kinds of input. Shortly thereafter, articles began appearing in the popular press touting the unique opportunities a parent has to sculpt their child’s developing brain.

For example, in 1996, an article on brain development in babies and young children by Susan Begley proclaimed to Newsweek’s three-million-plus[i] readers that: “[O]nce wired, there are limits to the brain’s ability to create itself. Time limits. Called ‘critical periods,’ they are windows of opportunity that nature flings open, starting before birth, and then slams shut, one by one, with every additional candle on the child’s birthday cake.”[ii] In the decade immediately after the Newsweek article was published, education policy makers and entrepreneurs continued to seize upon the notion of a “critical” period and capitalize on the push for more and more “learning” in infancy and preschool years. Parents—and children—are still suffering the consequences of this misleading view of how the brain develops and how children learn.

Parents have been bombarded by articles such as “To Shape a Life, We Must Begin Before a Child is 3”[iii] and “Building a Better Brain: A Child’s First Three Years Provide Parents Once-in-Lifetime Opportunity to Dramatically Increase Intelligence.” One book even claims that performing the “right” kind of learning alchemy in the first three years can boost a child’s IQ by up to thirty points![iv]

But what does “critical period” really mean? Where does this notion come from and what is the scientific evidence on so-called critical periods? And, more importantly, what are the implications for intuitive parenting? It turns out that the notion that a child’s brain must be wired before the age of three is highly misleading. In truth, brain plasticity continues throughout adolescence and into adulthood and basic brain architecture is not complete until adolescence—or even later. Every parent who has raised a child knows that the teenage brain is nothing like that of an adult and is not quite finished developing!

So where does the outright myth that parents have to hit every “critical period” before a child’s third birthday come from? In brain development and in developmental psychology, a critical period is a time window thought to be crucial for acquiring a mental ability. Language development is a well-known example of an accomplishment that research has shown begins during a critical period, meaning that if a child’s brain gets no language input from parents and others[v] by a certain time, the child will fail to develop language skills properly. Have you ever noticed that some people who learn a second language speak with an accent, even when their overall knowledge of its words and grammar is excellent? It turns out that if someone learns a second language before their teen years, he or she will probably not have an accent whereas those learning as teenagers, or later, probably will. There seems to be a critical period for learning a second language, at least in terms of pronouncing that second language like a native speaker, that ends at around age twelve.[vi] But it turns out that there are relatively few hard and fast “critical periods” and the inherent flexibility in brain development means that the notion of windows slamming shut with each candle on a birthday cake is simply not true. Indeed, modern brain scientists have by and large stopped even using the term “critical period” in favor of the more accurate “sensitive period.”

The truth is that the developing brain does indeed need input to become properly wired. Studies of people who are blind at birth show that the brain regions normally used for sight are converted to other duties, such as listening. And that even if sight is later restored, the visual centers in the brain are no longer able to process visual input properly. On the other hand, and this is a key point, even when a person has very low vision and nearly blind, when sight is restored, the vision centers in the brain work very well, even if sight is not completely restored until after the third—or even the tenth birthday! As long as there is some visual input, even if it is degraded in quality, the brain will be able to process visual information when it becomes fully available.

The take home message here is that the brain does NOT need specialized input to activate neural plasticity and become properly wired for a lifetime of learning. Instead, a parent simply needs to be sure a child—and her developing brain—have plenty of nurturing experience in the real world. Talking to your child, playing with them, reading to them, nurturing their inherent curiosity and simply having fun are even more powerful than flashcards, the latest learning app or “baby genius” DVD for activating neural plasticity and wiring the brain right on time.



[ii] Begley, S. “Your Child’s Brain.” Newsweek, February 19, 1996, 55–61.

[iii] Beck, Joan. “To Shape a Life, We Must Begin Before a Child Is 3.” Chicago Tribune, April 21, 1994.

[iv] Perlmutter, David, and Carol Colman. Raise a Smarter Child by Kindergarten: Build a Better Brain and Increase IQ Up to 30 Points. Bantam Dell Publishing Group, 2006.

[v] “The Development of Language: A Critical Period in Humans.” In Neuroscience. 2nd ed. D. Purves, G. J. Augustine, and D. Fitzpatrick, eds. Sunderland, MA: Sinauer Associates, 2001.

[vi] DeKeyser, Robert. “Age Effects in Second Language Learning.” In The Routledge Handbook of Second Language Acquisition, 2012, 442–460.

More from Psychology Today

More from Stephen Camarata Ph.D.

More from Psychology Today