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.