Annie Murphy Paul: What we learn before we're born (1)
My subject today is learning. And in that spirit, I want to spring on you all a pop quiz. Ready? When does learning begin? Now as you ponder that question, maybe you're thinking about the first day of preschool or kindergarten, the first time that kids are in a classroom with a teacher. Or maybe you've called to mind the toddler phase when children are learning how to walk and talk and use a fork. Maybe you've encountered the Zero-to-Three movement, which asserts that the most important years for learning are the earliest ones. And so your answer to my question would be: Learning begins at birth.
Well today I want to present to you an idea that may be surprising and may even seem implausible, but which is supported by the latest evidence from psychology and biology. And that is that some of the most important learning we ever do happens before we're born, while we're still in the womb. Now I'm a science reporter. I write books and magazine articles. And I'm also a mother. And those two roles came together for me in a book that I wrote called "Origins." "Origins" is a report from the front lines of an exciting new field called fetal origins. Fetal origins is a scientific discipline that emerged just about two decades ago, and it's based on the theory that our health and well-being throughout our lives is crucially affected by the nine months we spend in the womb. Now this theory was of more than just intellectual interest to me. I was myself pregnant while I was doing the research for the book. And one of the most fascinating insights I took from this work is that we're all learning about the world even before we enter it.
When we hold our babies for the first time, we might imagine that they're clean slates, unmarked by life, when in fact, they've already been shaped by us and by the particular world we live in. Today I want to share with you some of the amazing things that scientists are discovering about what fetuses learn while they're still in their mothers' bellies. First of all, they learn the sound of their mothers' voices. Because sounds from the outside world have to travel through the mother's abdominal tissue and through the amniotic fluid that surrounds the fetus, the voices fetuses hear, starting around the fourth month of gestation, are muted and muffled. One researcher says that they probably sound a lot like the the voice of Charlie Brown's teacher in the old "Peanuts" cartoon. But the pregnant woman's own voice reverberates through her body, reaching the fetus much more readily. And because the fetus is with her all the time, it hears her voice a lot. Once the baby's born, it recognizes her voice and it prefers listening to her voice over anyone else's.
How can we know this? Newborn babies can't do much, but one thing they're really good at is sucking. Researchers take advantage of this fact by rigging up two rubber nipples, so that if a baby sucks on one, it hears a recording of its mother's voice on a pair of headphones, and if it sucks on the other nipple, it hears a recording of a female stranger's voice. Babies quickly show their preference by choosing the first one. Scientists also take advantage of the fact that babies will slow down their sucking when something interests them and resume their fast sucking when they get bored. This is how researchers discovered that, after women repeatedly read aloud a section of Dr. Seuss' "The Cat in the Hat" while they were pregnant, their newborn babies recognized that passage when they hear it outside the womb. My favorite experiment of this kind is the one that showed that the babies of women who watched a certain soap opera every day during pregnancy recognized the theme song of that show once they were born. So fetuses are even learning about the particular language that's spoken in the world that they'll be born into.
A study published last year found that from birth, from the moment of birth, babies cry in the accent of their mother's native language. French babies cry on a rising note while German babies end on a falling note, imitating the melodic contours of those languages. Now why would this kind of fetal learning be useful? It may have evolved to aid the baby's survival. From the moment of birth, the baby responds most to the voice of the person who is most likely to care for it -- its mother. It even makes its cries sound like the mother's language, which may further endear the baby to the mother, and which may give the baby a head start in the critical task of learning how to understand and speak its native language.
But it's not just sounds that fetuses are learning about in utero. It's also tastes and smells. By seven months of gestation, the fetus' taste buds are fully developed, and its olfactory receptors, which allow it to smell, are functioning. The flavors of the food a pregnant woman eats find their way into the amniotic fluid, which is continuously swallowed by the fetus. Babies seem to remember and prefer these tastes once they're out in the world. In one experiment, a group of pregnant women was asked to drink a lot of carrot juice during their third trimester of pregnancy, while another group of pregnant women drank only water. Six months later, the women's infants were offered cereal mixed with carrot juice, and their facial expressions were observed while they ate it. The offspring of the carrot juice drinking women ate more carrot-flavored cereal, and from the looks of it, they seemed to enjoy it more.
A sort of French version of this experiment was carried out in Dijon, France where researchers found that mothers who consumed food and drink flavored with licorice-flavored anise during pregnancy showed a preference for anise on their first day of life, and again, when they were tested later, on their fourth day of life. Babies whose mothers did not eat anise during pregnancy showed a reaction that translated roughly as "yuck." What this means is that fetuses are effectively being taught by their mothers about what is safe and good to eat. Fetuses are also being taught about the particular culture that they'll be joining through one of culture's most powerful expressions, which is food. They're being introduced to the characteristic flavors and spices of their culture's cuisine even before birth.