Your Baby from Birth to 3 Months

Your Infant's Brain & Development

We leave our mother's womb when we're ready. But when a human baby arrives in the world, she is far from finished. Compare a human newborn to a puppy: An 8-week-old puppy runs, plays, eats, and drinks on his own; a human baby of the same age can barely see and can't control her arms and legs. Why? The newborn nervous system and brain are only partly developed, says Dr. Steiner, and the brain is the central command center for the rest of the body. At birth, a baby's brain weighs only a quarter of an adult's brain. It's capable of controlling his most vital functions, such as breathing, crying, sleeping, and feeding. However, the cerebral cortex -- the area of the brain that controls more sophisticated thinking and emotions -- is still growing and developing to allow him to act in accordance with his will rather than simply react to his environment.

So how does a newborn go from a helpless bundle to a laughing, learning infant? At birth, a baby has 100 billion neurons (brain cells). But neurons alone don't spur growth and abilities. In order for baby to get the hang of everything from tracking an object with his eyes to smiling, those brain cells need to connect with one another, sprouting long dendrites, which form bridges between cells. These brain-cell connections are called synapses. When baby is born, he doesn't have many synapses, which is yet another reason he's unfinished: An infant's brain transmits information about 16 times more slowly than an adult's. Speeding up that transmission takes time, too; at birth, your newborn's brain cells are only beginning to develop myelin, a dense, fatty substance that accelerates connections. In the first 3 months of life alone, your baby's brain synapses will multiply more than 20 times.

Your Role in Baby's Brain Development

But your baby's "finishing touches" don't just happen automatically. New research confirms that brain development is "activity-dependent." Every experience your baby has -- from staring at that black-and-white mobile you hang over the crib to learning that cries bring food or comfort -- excites certain neural circuits and leaves others inactive. So what does all this mean to a parent? You needn't break out the flash cards. Talking to your baby, rocking him -- all of the normal parent-child interactions that occur in early life -- contribute to brain growth and make baby smarter.

According to T. Berry Brazelton, MD, professor of pediatrics at Harvard University and author of dozens of parenting books, the most important reason our brains aren't fully formed at birth is that humans are social beings who live and work together in a community. "Individuality isn't as important to a puppy or a giraffe as it is to humans," says Dr. Brazelton. "Our individual differences would be at risk if we were born any more competent. But make no mistake. We continue to be amazed at babies' competence. They take in cues from their environment remarkably early, learning and laying down memories."

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