Through the first three years of life, your child's brain is hard at work, making more connections than it ever will again. In fact, a 3-year-old's brain is more active than the brain of a young adult, according to a webpage about development published by North Dakota State University. There's a lot going on in your child's developing brain, and the environment you provide early in life makes a difference.
Early Childhood
Your brain is jam-packed with specialized cells called neurons, which communicate through electric signalling via axons and dendrites, long extensions that emerge from each neuronal cell body. Your baby's brain adds relatively few new neurons after birth, but the number of connections between neurons explodes during the first three years of life. The junction that two neurons use to communicate is called a synapse, and the number of synapses in your baby's brain continues to multiply as cells grow new axons and dendrites. By age three, each of your child's neurons has made 10,000 connections, equivalent to a total of a quadrillion synapses throughout the brain.
Later Childhood
Synapse formation slows after the toddler years, and your child's brain starts to eliminate unused connections around age 11, a process called synaptic pruning. By getting rid of excess connections, your child's brain becomes more efficient and well-adapted to his specific environment. By your child's mid- to late teens, the number of connections in her brain approaches the number found in adults.
In the human nervous system, axons get covered by a substance called myelin, which protects and nourishes neurons while also speeding up signal transmission. Myelination of neurons begins at birth, but continues well through childhood. Some sections of the brain aren't fully myelinated until much later in life. The prefrontal cortex, a brain area responsible for abstract reasoning and higher-order thinking, is one example of a structure that gets myelinated relatively late in development.
Critical Periods
Although adult neurons can build connections to reflect new learning, children's brains are considered more "plastic" --- capable of change in response to new information --- because of the early proliferation of synapses. Scientists propose that there are prime periods for learning, during which kids can pick up certain skills and abilities more quickly and effectively than at any other time in life. For example, children need sensory input for full development of the visual system. Your child's sight doesn't approach adult levels until his second birthday, and visual deprivation before this point can affect normal vision development. Similarly, children need to hear language through their first few years of life to maximize their abilities to speak and understand later.
Are Girls and Boys Different?
There are differences in male and female brain structure and development, but "Scientific American" writer Lise Eliot warns against overemphasizing these differences or seeing them as hardwired. Girls really do mature faster than boys, at least when it comes to brain development. Synaptic pruning occurs two years earlier in girls than it does in boys. However, it's still unclear how specific structural differences relate to behavioral differences, and how those differences relate to biological gender. A University of Iowa study suggested that empathy is linked to personality traits typically considered "feminine," rather than to a person's physical sex. On the other hand, scientists know that sex hormones affect brain organization, but concede that experience influences gene expression, too. What scientists know for sure: your child's brain development, personality and talents are the result of a complex interplay of factors, including gender and experience in the world.
References
- North Dakota State University; Understanding Brain Development in Young Children; Sean Brotherson; April 2005
- The Dana Foundation; Brain Development in Childhood --- The Dana Guide; Ann MacDonald; November 2007
- "NIH Record"; Male/Female Differences Offer Insight Into Brain Development; Charlotte Armstrong
- "Scientific American"; The Truth About Boys and Girls; Lise Eliot; April 2010
- "Scientific American"; Boy Brain, Girl Brain?; Lise Eliot; September 2009
