my subject today is learning. and in that spirit, i want to spring on youall a pop quiz. ready? when does learning begin? now as you ponder thatquestion, maybe you're thinking about the first day of preschool orkindergarten, the first time that kids are in a classroom with a teacher. ormaybe you've called to mind the toddler phase when children are learning how towalk and talk and use a fork. maybe you've encountered the zero-to-threemovement, which asserts that the most important years for learning are theearliest ones. and so your answer to my question would be: learning begins atbirth.
well today i want to present to you an idea that may be surprising and mayeven seem implausible, but which is supported by the latest evidence frompsychology and biology. and that is that some of the most important learning weever do happens before we're born, while we're still in the womb. now i'm ascience 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 e_citing new fieldcalled fetal origins. fetal origins is a scientific discipline that emerged justabout two decades ago, and it's based on the theory that our health andwell-being throughout our lives is crucially affected by the nine months wespend in the womb. now this theory was of more than just intellectual interestto me. i was myself pregnant while i was doing the research for the book. andone of the most fascinating insights i took from this work is that we're alllearning about the world even before we enter it.
when we hold our babies for the first time, we might imagine that they'reclean slates, unmarked by life, when in fact, they've already been shaped by usand by the particular world we live in. today i want to share with you some ofthe amazing things that scientists are discovering about what fetuses learnwhile they're still in their mothers' bellies.
first of all, they learn the sound of their mothers' voices. because soundsfrom the outside world have to travel through the mother's abdominal tissue andthrough the amniotic fluid that surrounds the fetus, the voices fetuses hear,starting around the fourth month of gestation, are muted and muffled. oneresearcher says that they probably sound a lot like the the voice of charliebrown's teacher in the old "peanuts" cartoon. but the pregnant woman's own voicereverberates through her body, reaching the fetus much more readily. and becausethe fetus is with her all the time, it hears her voice a lot. once the baby'sborn, it recognizes her voice and it prefers listening to her voice over anyoneelse's.
how can we know this? newborn babies can't do much, but one thing they'rereally good at is sucking. researchers take advantage of this fact by rigging uptwo rubber nipples, so that if a baby sucks on one, it hears a recording of itsmother's voice on a pair of headphones, and if it sucks on the other nipple, ithears a recording of a female stranger's voice. babies quickly show theirpreference by choosing the first one. scientists also take advantage of the factthat babies will slow down their sucking when something interests them andresume their fast sucking when they get bored. this is how researchersdiscovered that, after women repeatedly read aloud a section of dr. seuss' "thecat in the hat" while they were pregnant, their newborn babies recognized thatpassage when they hear it outside the womb. my favorite e_periment of this kindis the one that showed that the babies of women who watched a certain soap operaevery day during pregnancy recognized the theme song of that show once they wereborn. so fetuses are even learning about the particular language that's spokenin the world that they'll be born into.
a study published last year found that from birth, from the moment ofbirth, babies cry in the accent of their mother's native language. french babiescry on a rising note while german babies end on a falling note, imitating themelodic contours of those languages. now why would this kind of fetal learningbe useful? it may have evolved to aid the baby's survival. from the moment ofbirth, the baby responds most to the voice of the person who is most likely tocare for it -- its mother. it even makes its cries sound like the mother'slanguage, which may further endear the baby to the mother, and which may givethe baby a head start in the critical task of learning how to understand andspeak its native language.
but it's not just sounds that fetuses are learning about in utero. it'salso tastes and smells. by seven months of gestation, the fetus' taste buds arefully developed, and its olfactory receptors, which allow it to smell, arefunctioning. the flavors of the food a pregnant woman eats find their way intothe amniotic fluid, which is continuously swallowed by the fetus. babies seem toremember and prefer these tastes once they're out in the world. in onee_periment, a group of pregnant women was asked to drink a lot of carrot juiceduring their third trimester of pregnancy, while another group of pregnant womendrank only water. si_ months later, the women's infants were offered cerealmi_ed with carrot juice, and their facial e_pressions were observed while theyate it. the offspring of the carrot juice drinking women ate morecarrot-flavored cereal, and from the looks of it, they seemed to enjoy itmore.
a sort of french version of this e_periment was carried out in dijon,france where researchers found that mothers who consumed food and drink flavoredwith licorice-flavored anise during pregnancy showed a preference for anise ontheir first day of life, and again, when they were tested later, on their fourthday of life. babies whose mothers did not eat anise during pregnancy showed areaction that translated roughly as "yuck." what this means is that fetuses areeffectively 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 bejoining through one of culture's most powerful e_pressions, which is food.they're being introduced to the characteristic flavors and spices of theirculture's cuisine even before birth.
now it turns out that fetuses are learning even bigger lessons. but beforei get to that, i want to address something that you may be wondering about. thenotion of fetal learning may conjure up for you attempts to enrich the fetus --like playing mozart through headphones placed on a pregnant belly. but actually,the nine-month-long process of molding and shaping that goes on in the womb is alot more visceral and consequential than that. much of what a pregnant womanencounters in her daily life -- the air she breathes, the food and drink sheconsumes, the chemicals she's e_posed to, even the emotions she feels -- areshared in some fashion with her fetus. they make up a mi_ of influences asindividual and idiosyncratic as the woman herself. the fetus incorporates theseofferings into its own body, makes them part of its flesh and blood. and oftenit does something more. it treats these maternal contributions as information,as what i like to call biological postcards from the world outside.
so what a fetus is learning about in utero is not mozart's "magic flute"but answers to questions much more critical to its survival. will it be borninto a world of abundance or scarcity? will it be safe and protected, or will itface constant dangers and threats? will it live a long, fruitful life or ashort, harried one? the pregnant woman's diet and stress level in particularprovide important clues to prevailing conditions like a finger lifted to thewind. the resulting tuning and tweaking of a fetus' brain and other organs arepart of what give us humans our enormous fle_ibility, our ability to thrive in ahuge variety of environments, from the country to the city, from the tundra tothe desert.
to conclude, i want to tell you two stories about how mothers teach theirchildren about the world even before they're born. in the autumn of 1944, thedarkest days of world war ii, german troops blockaded western holland, turningaway all shipments of food. the opening of the nazi's siege was followed by oneof the harshest winters in decades -- so cold the water in the canals frozesolid. soon food became scarce, with many dutch surviving on just 500 calories aday -- a quarter of what they consumed before the war. as weeks of deprivationstretched into months, some resorted to eating tulip bulbs. by the beginning ofmay, the nation's carefully rationed food reserve was completely e_hausted. thespecter of mass starvation loomed. and then on may 5th, 1945, the siege came toa sudden end when holland was liberated by the allies.
the "hunger winter," as it came to be known, killed some 10,000 people andweakened thousands more. but there was another population that was affected --the 40,000 fetuses in utero during the siege. some of the effects ofmalnutrition during pregnancy were immediately apparent in higher rates ofstillbirths, birth defects, low birth weights and infant mortality. but otherswouldn't be discovered for many years. decades after the "hunger winter,"researchers documented that people whose mothers were pregnant during the siegehave more obesity, more diabetes and more heart disease in later life thanindividuals who were gestated under normal conditions. these individuals'prenatal e_perience of starvation seems to have changed their bodies in myriadways. they have higher blood pressure, poorer cholesterol profiles and reducedglucose tolerance -- a precursor of diabetes.
why would undernutrition in the womb result in disease later? onee_planation is that fetuses are making the best of a bad situation. when food isscarce, they divert nutrients towards the really critical organ, the brain, andaway from other organs like the heart and liver. this keeps the fetus alive inthe short-term, but the bill comes due later on in life when those other organs,deprived early on, become more susceptible to disease.
but that may not be all that's going on. it seems that fetuses are takingcues from the intrauterine environment and tailoring their physiologyaccordingly. they're preparing themselves for the kind of world they willencounter on the other side of the womb. the fetus adjusts its metabolism andother physiological processes in anticipation of the environment that awaits it.and the basis of the fetus' prediction is what its mother eats. the meals apregnant woman consumes constitute a kind of story, a fairy tale of abundance ora grim chronicle of deprivation. this story imparts information that the fetususes to organize its body and its systems -- an adaptation to prevailingcircumstances that facilitates its future survival. faced with severely limitedresources, a smaller-sized child with reduced energy requirements will, in fact,have a better chance of living to adulthood.
the real trouble comes when pregnant women are, in a sense, unreliablenarrators, when fetuses are led to e_pect a world of scarcity and are borninstead into a world of plenty. this is what happened to the children of thedutch "hunger winter." and their higher rates of obesity, diabetes and heartdisease are the result. bodies that were built to hang onto every calorie foundthemselves swimming in the superfluous calories of the post-war western diet.the world they had learned about while in utero was not the same as the worldinto which they were born.
here's another story. at 8:46 a.m. on september 11th, __, there were tensof thousands of people in the vicinity of the world trade center in new york --commuters spilling off trains, waitresses setting tables for the morning rush,brokers already working the phones on wall street. 1,700 of these people werepregnant women. when the planes struck and the towers collapsed, many of thesewomen e_perienced the same horrors inflicted on other survivors of the disaster-- the overwhelming chaos and confusion, the rolling clouds of potentially to_icdust and debris, the heart-pounding fear for their lives.
about a year after 9/11, researchers e_amined a group of women who werepregnant when they were e_posed to the world trade center attack. in the babiesof those women who developed post-traumatic stress syndrome, or ptsd, followingtheir ordeal, researchers discovered a biological marker of susceptibility toptsd -- an effect that was most pronounced in infants whose mothers e_periencedthe catastrophe in their third trimester. in other words, the mothers withpost-traumatic stress syndrome had passed on a vulnerability to the condition totheir children while they were still in utero.
now consider this: post-traumatic stress syndrome appears to be a reactionto stress gone very wrong, causing its victims tremendous unnecessary suffering.but there's another way of thinking about ptsd. what looks like pathology to usmay actually be a useful adaptation in some circumstances. in a particularlydangerous environment, the characteristic manifestations of ptsd -- ahyper-awareness of one's surroundings, a quick-trigger response to danger --could save someone's life. the notion that the prenatal transmission of ptsdrisk is adaptive is still speculative, but i find it rather poignant. it wouldmean that, even before birth, mothers are warning their children that it's awild world out there, telling them, "be careful."
let me be clear. fetal origins research is not about blaming women for whathappens during pregnancy. it's about discovering how best to promote the healthand well-being of the ne_t generation. that important effort must include afocus on what fetuses learn during the nine months they spend in the womb.learning is one of life's most essential activities, and it begins much earlierthan we ever imagined.
thank you.
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