Why you need to (gently) rock, swing, and spin your baby more.

Most parents intuitively understand that the way they interact with their children influences the kind of people their little ones will become. What may be a surprise, however, is how specific types of stimulation a child experiences early in life affect the way her brain actually develops. Here are some interesting connections that researchers have revealed.

Why Rocking Improves Reflexes

Everyone knows that babies enjoy being rocked, but it turns out that infants who are subjected to repetitive motion—such as rocking, swinging, bouncing, or spinning—have more mature reflexes and motor skills, are less irritable, are more visually aware, and spend more time in the state of calm alertness that’s conducive to absorbing information about the world around them. In a study published in Science, babies from 3 to 13 months who had repeated chair-spinning sessions during the course of a month (they sat on the lap of a researcher on a swivel chair) showed more accelerated development of reflexes and motor skills (in particular, sitting, crawling, standing, and walking) than babies who didn’t receive the stimulation.

Researchers suspect that because the vestibular system—the sensory system in the inner ear that gives us our sense of balance and spatial orientation—is early to mature, it plays a critical role in organizing other sensory and motor abilities. And this type of stimulation provides it with an early boost, helping infants to more readily navigate their environment.

When Angry Voices Stress the System

No one likes listening to their parents argue, but who knew that infants—even sleeping infants—have distinctly negative reactions when exposed to angry voices? Mothers of 6- to 12-month-olds who took part in a study conducted at the University of Oregon were asked to rate the amount of conflict that occurred in their homes. While their babies were sleeping, researchers placed headphones on each infant and played recordings of voices that were happy, angry, or neutral. All of the infants reacted to the voices, but the brain activity among infants who came from homes where parents frequently fought was significantly higher in response to the angry voices. And that heightened activity occurred in regions of the brain where altered functioning has been linked to emotional stress and mood disorders in adolescents.

How Nurturing Changes the Brain

Researchers from the Washington University School of Medicine measured the level of emotional support a group of 92 children ages 3 to 5 received from their caregivers (primarily mothers) while the children were performing mildly stressful tasks. They repeated the experiment once each year for six years. At ages 7 to 10, each child underwent an MRI (magnetic resonance imaging) to measure the volume of the hippocampus, a region of the brain that plays a key role in learning, memory, stress modulation, emotional regulation, and spatial navigation. The children whose mothers had been more supportive and patient had hippocampal volumes nearly 10 percent greater than those of the other children.

In adults, studies have linked greater hippocampal volume to increased psychological resilience (for instance, in recovering from post-traumatic stress disorder) and better spatial memory. Smaller hippocampal volumes, on the other hand, have been associated with depression and Alzheimer’s.

Emphasis on Early Experiences

One point all of these studies bring home is how key the early years are. Babies are born with nearly all the brain cells they’ll need for life (about 100 billion, in case you’re wondering). During the early months and years, these existing neurons sprout branches, forming a weblike network across which messages pass from one region of the brain to another. This connectivity allows for increasingly complex brain function. In short, the more these pathways are stimulated, the stronger they become, which is why the kind of stimuli your child is exposed to is so critical to her development.

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