Your baby coos, and you coo back. She waves a little hand, and you wave, too. These are natural everyday interactions—but they’re also crucial contributions to your baby’s step-by-step development.

Even simple exchanges stimulate the neural connections that are rapidly forming in your infant’s growing brain. The more she practices new sounds and motions, however small, the stronger and faster those neural circuits become. And research demonstrates that, once mastered, each skill becomes the foundation for the next one, ultimately building the diverse capabilities of a walking, talking child.

Learning to Grasp, One Reach at a Time

A crucial skill that develops in this cumulative manner, for instance, is your baby’s ability to reach out and grasp objects around her—an essential tool for exploring her physical world.

The earliest stages of reaching and grasping begin subtly, shortly after birth, with prereaching, or the extension of the shoulder, arm, and hand at once. At this stage, an infant’s movements are still mainly inborn reflexes, governed by nerve cells deep in the brain stem and spinal cord. As your baby’s brain matures during her first year of life, new connections rapidly form in the motor cortex, a narrow strip of neurons that wraps around the outer edge of the brain from ear to ear. Critical growth occurs at the same time in the nerve fibers, called the corticospinal tract, that travel from the motor cortex down the spinal cord to reach the neurons controlling movement throughout the body.

All that neural growth enables a child’s movements to become less reflexive and more deliberate. And it quickly translates into a sequence of gains for grasping. Around 4 months, your infant will likely surpass prereaching and succeed at gripping that block or rattle before her. This small triumph is possible because the corticospinal fibers have by then reached the nerve cells governing movement in the arms and hands. By the time your baby is 7 to 12 months, the neural connections to the wrists and fingers are mature enough to bring your baby a big breakthrough: the pincer grasp, the gripping of objects between thumb and finger.

The increasing speed and precision of your baby’s movements is helped along by the growth of insulation, or myelin, along the corticospinal fibers. Soon she’ll be performing feats of precision, such as spinning wheels, pulling levers, and fastening buttons.

Still, your infant has more to learn. Researchers in the United Kingdom and the Netherlands observed 35 infants, ages 6 months to 20 months, to see how they refined their repertoire of grips. The younger babies predominantly used power grips (clamping between the finger pads and palm). As they moved into their second year, however, the babies opted for precision grips (between finger and thumb) more often, using fewer fingers for each grasp.

From Sounds to Words

In a similar way as grasping, a critical foundation for language development is laid even before your child starts to talk. Babies are born with the ability to distinguish individual sounds in human speech, such as b or g. Babbling, which is practice for talking, begins around 4 months, as the neural circuits to the speech muscles around the mouth get their myelin. But infants must still learn to make words of those sounds, understand the meaning, and eventually combine them into phrases and sentences—and research shows this learning can only happen when the neural pathways are stimulated by social interaction. It’s therefore important to start activating your baby’s language learning circuits as early as possible, simply by talking to her.

Surprisingly, it actually helps to speak in what’s often called parent-ese. Studies show that the exaggerated, singsong speech parents use instinctively with their babies may serve an important developmental purpose. Researchers at Carnegie Mellon University and University of Wisconsin found evidence that 6- to 8-month-olds were able to distinguish the boundaries between words in melodic baby talk but not in a flatter adult tone. A study at the University of Washington showed that the more a mother tended to stretch out her vowels, baby talk style, the better her infant’s speech perception performance was.

Scientists are still sorting out exactly which structures in the brain work together to create speech. What’s clear is that it’s a complex skill involving robust connections among the brain areas responsible for hearing (the auditory cortex), recognizing words (Wernicke’s area), and commanding the mouth to move and form words (Broca’s area). And—as with the neural circuits involved in reaching and grasping—those connections can grow only with repeated stimulation and use.

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