Parents are always reassured to see their developing baby’s organs on prenatal ultrasounds; when the ultrasound technician points out the heart, kidneys, and brain, you are relieved to find your baby developing on schedule. Once your baby is here, developmental stages are, of course, far more obvious, but that doesn’t mean you know just what happens during your child’s brain development.

The years from birth to three are critical in brain development, and many rapid changes take place during that time. The process is a complex one, but there are general guidelines that can help you understand this developmental process.

The website zerotothree.com offers a broad overview of postnatal brain development. According to the site, the neural circuits that control vital bodily functions such as swallowing, breathing, and heartbeat are in place at birth, but the rest of the brain takes time to develop. This means that a baby’s experience and environment will shape his brain development.

Newborns’ behavior is controlled largely by the lower brain. Kicking, sleeping, rooting, and feeding are governed by the brain stem and spinal cord. Further development happens leisurely, and allows you to watch as your baby’s mind takes shape.

Babies have poorly connected neurons at birth, but they develop with astonishing rapidity. With these developments come milestones such as a strong attachment to parents or a pincer grasp. By age two, a toddler’s synapses have grown to well over a hundred trillion, and the visual cortex and primary touch areas of the brain are taking off. Higher cognitive and emotional functions develop more slowly, but this peak in synapse development lasts through age four to eight.

The development of the brain is dependent on activity, so the activities in the motor, emotional, cognitive, and sensory circuits shape the way that circuit develops. Every new experience affects some circuits and leaves other inactive.

The process by which those that are not affected drop away is called “pruning,” which sounds devastating, but actually is not. If all synapses were stimulated at once, a child’s processing of material would not be streamlined, and children wouldn’t be able to walk, talk or see.

Babies are hard-wired to prefer human stimuli, such as voice, touch, and face, and parents are also programmed to respond to babies’ cues. Brain development relies heavily on early experience, and it is no coincidence that the nurturing attention most adults are “programmed” to give babies is just what babies need to stimulate their growing brains.

Language stimulation has been proven to make a difference in babies’ brain development. Infants and children who are talked to, read to, and otherwise engaged in verbal stimulation and interaction have more advanced linguistic skills than those who do are not so stimulated.

Although there has been a lot of hype over what caregivers can do to make infants “smarter,” natural nurturing instincts such as talking to, showing physical affection toward, and listening to your baby’s cues will assist in your baby’s development during the critical brain development years