By the time she was 9 months old, my daughter Grace knew what to do when I asked, "How big are you?" "So big!" I'd say, laughing, as she raised her arms in the air so I could pull a clean shirt over her head. She couldn't have known I was referring to her size, but by a process of repetition and imitation she learned that the question meant it was time to put on a clean shirt.
At 16 months, she'd say, "Bo bee" -- her version of "So big" -- when she wanted to put on a shirt that she'd picked from the laundry basket. By listening, remembering, and imitating, she'd learned to connect words with actions.
By 18 months, Grace showed us that she understood the meaning of the word "big." One day, she lifted her shirt to reveal her Buddha belly, a feature that her father and I had often praised. With a proud smile, she announced, "I big belly!" It was her first sentence.
Watching a baby's mental development is one of the most amazing experiences a parent will ever have. Just as Grace did with her dad and me, your infant will give you clues as to what's going on in her mind. Research also gives us some exciting insights.
Let the Learning Begin
At birth babies' brains have 100 billion neurons -- as many as they will ever have. As a baby grows, so do these neurons, forming branches that connect with other neurons to transmit signals and share information.
Compared to most other animals, humans have a huge number of brain cells. "It's as if nature decided, 'We want these guys to have enormous brains, but we can't make their bodies six times larger, so we're going to cut pregnancy short and get these things out before the head becomes too big,'" says Alan Leslie, Ph.D., professor of psychology and cognitive science at Rutgers University in New Brunswick, NJ. As a result, human babies are born with brains that aren't fully developed.
Each bit of information a baby takes from his environment stimulates a different part of the brain and reinforces particular neural connections. In the first two months alone, the number of these connections increases from an estimated 50 trillion to 1,000 trillion.
The learning starts with the sounds and sensations a baby experiences before he's even born. At birth, the sense of hearing is more developed than vision. "Full-term infants have the benefit of having heard their mother's voice for weeks preceding delivery," says Charles Nelson, Ph.D., professor of child psychology, neuroscience, and pediatrics at the University of Minnesota's Institute of Child Development in Minneapolis. Nelson has monitored newborns less than 24 hours old and found that when a newborn hears his mother's voice, he shows a different pattern of brain activity than when he hears a stranger's.
Outward evidence of a baby's learning and thinking is subtle at first: the newborn modifying his sucking to adapt to the breast, bottle, or pacifier; the 3-week-old who takes a break from feeding to look into her mother's eyes. Because a newborn's vision is believed to be no better than 20/400 -- meaning he sees things at 20 feet away as a person with perfect vision would see them from 400 feet away -- he can focus only on things within seven to ten inches from his face. So he is more attracted to stark contrasts, such as black and white. But as the connections between neurons in the brain's visual cortex increase, a baby begins to see more clearly. His depth perception also develops as he begins to coordinate his eye movements so that both eyes focus on the same thing at the same time. Now a baby may become fascinated by the finer features of a toy or his parents' faces, noticing three-dimensional details rather than looking only at the edges of objects.
By the time babies are 2 to 3 months old, they'll begin watching people as they walk across the room and be able to make eye contact with Mom and Dad. At this point, vision improves enough that babies are ready for new things to stimulate them (while still being attracted to the details of familiar objects that they are only now noticing). Vision improves to 20/60 or better around 6 months of age, allowing your little bundle to distinguish your face from the sea of adult faces he's already encountered.
Nelson believes that this ability to recognize caretakers also sparks a primitive understanding of cause and effect: "When I'm hungry, one of them feeds me," thinks the baby. An infant may look across the room toward the refrigerator because she's learned that bottles come from there. A breastfed baby may look at Mom the same way, as if to say, "Hey, there's the one with the milk!"
By 4 to 5 months of age, a baby will visually follow an object -- such as a spoon or a rattle -- when it falls out of her hand, marking the beginning of her understanding that she is separate from other people and things around her. Simple hiding games and rounds of peekaboo help a baby learn that objects and people still exist when she can't see them, and this leads to her ability to draw mental pictures of things that are not right in front of her. This could be the first step toward an active imagination.
Cracking the Code
As your baby's brain develops, you'll be delighted by those surprising moments when your tot lets you in on how much he's learned so far. Ami Day of St. Louis, MO, got a taste of this when her daughter, Mackenzie Ekren, started babbling out conversations at 6 months of age. "Her tone varied," said Day. "It wasn't a monotone like I thought it would be." Mackenzie showed that she understood the give-and-take of conversations by ending her stream of sounds to wait for a response. If there was none, she arched her eyebrows expectantly, waiting for her mother's reply. Her mother held up her end of the conversation either by saying something or by imitating her daughter's babbling, which gave Mackenzie enough reinforcement to mimic her mother right back and to try to outtalk her.
Interactions like this mark huge strides in cognitive development. "A baby is beginning to crack into the huge world of encoded communication that flies around -- what we call language," says Leslie. As the baby's babbling becomes more distinct (around 8 to 10 months), parents begin to wonder if she is actually forming words: "mama," "dada," or even complex phrases. But in general, babies this age don't associate words with meanings. Even if they say, "mama," they don't yet know that's your name. Around 10 to 12 months of age, they will start to acknowledge that words have meanings, but they may use one word for several purposes. For instance, a 1-year-old may use "cookie" to say, "I want a cookie," "I'm hungry," "That's a cookie," or a plethora of other things she associates with that particular word.
By babbling, a baby practices forming the varied sounds of her native language, with parents trying to help by providing lots of verbal input. When Margie Gitten, of Weston, FL, pointed to the polka dots on the nursery wall, she named each color for her daughter Emily. Emily cocked her head and looked as if she was registering the information. Although the 7-month-old wasn't yet able to learn colors, the interaction with her mom eventually helped her understand how groups of sounds form words, and how words represent things in her world.
By 8 months, babies begin to retain words in their long-term memory, even though they don't comprehend their meanings. In one study, researchers who read a story to a group of infants found that the babies recognized words from that story two weeks later. At that time, the researchers read a list of words to the infants and noted that they listened significantly longer to words from the story than to unfamiliar words. At 12 months of age, most infants have retained enough information to understand 50 words, and by 18 months, they'll probably be able to use those words themselves.
As an infant's physical relationship to the world shifts from lying down to sitting, crawling, and walking, it's difficult to separate mental development from motor development. "Mobility has an enormous impact in terms of how much useful information the infant can obtain," says Leslie, who compares this advantage to adding a telescopic lens to your camera. "If the baby wants to zoom in on something, now he can stand up and walk toward it. He can even pick it up and put it in his mouth for good measure. Being able to move around allows the baby to bring that fantastic brain into contact with more of the world."
Your Important Role
Most parents already know that infants thrive on attention. Our instincts tell us to cuddle, talk, read, and play games with our children. Plenty of attention and interaction with your little one gives her two great gifts: the chance to explore her physical universe, and the knowledge that she is worthy of her parents' time and love. Despite all that we know about our babies' developing brains, each infant is born with a distinct personality and potential. Day by day, she'll offer up more insights about who she is. It's a mystery that is revealed all too quickly, since by the time she's a toddler, few of her thoughts are likely to go unexpressed.
Linda Henry, a mother of two, is the author of the "Of Woodstoves and Websites" column of the Lake Country Journal Magazine in Minnesota.