Sunday, January 6, 2013
Listen to Mama: What Newborns Learned Before Birth, and Some Implications
The “mother tongue” or the “cradle language”-- that’s what we call our earliest, and usually most fluent, language. We learn about its words and grammar from our earliest caregivers, of course, but for quite a while people have been suspecting that some features of language are learned before birth as well as after.
Like other sensitivities to touch stimulation, hearing-- the result of bending of hair-like cells in the inner ear—is well-developed before birth. Although human beings are specialized for hearing sound waves traveling through air, we can pick up sounds moving through water, or even through the earth (how they hear the stampede coming in cowboy movies, right?). This means it’s not so surprising that some sound waves resulting from speech can travel through a pregnant woman’s body and through the amniotic fluid to cause responses in the ears of an unborn baby even several months before birth.
But, so what if this does happen? Do those speech sound waves have any effect on the baby’s development, any more than do other sounds like a car starting, a dog barking, or mother’s teeth being brushed? The fact that something can happen doesn’t mean it does happen, so back in the 1980s researchers started looking to see whether newborns showed any effects of systematic speech sound experiences in the weeks before birth.
Well-known studies by DeCasper and others in the ‘80s had mothers-to-be record their voices reading either The Cat in the Hat or a similar-sounding story, The Dog in the Fog. The women did not know at the time they recorded which story they would later be asked to “read to their bellies” so the developing fetus could hear. Stories were randomly assigned and read repeatedly over the last weeks of the pregnancies. After they were born, the babies were allowed to listen to both stories and could control which one they heard by sucking on an artificial nipple. They spent more time listening to the story they had heard prenatally than to the other, very similar story, suggesting that they had been learning as they listened.
But there is an oddity in these results. The evidence is clear that the babies could tell the difference between the familiar and the unfamiliar sounds, and they showed us this by choosing to listen for a longer time to one story than they did to the other. But… newborn babies don’t usually pay more attention to familiar than to unfamiliar things, the way older babies and adults often do. Newborn babies show a tendency to habituate to things they’ve seen or heard before. After paying attention to familiar things briefly, they stop paying attention to them, and spend much more time attending to unfamiliar sights or sounds. The extent to which newborns do this is correlated with their later cognitive development. Yet DeCasper and his colleagues reported that the newborns in their study paid more attention to the sounds they had heard before. What was this about? Was it that because those sounds were not heard through the mothers’ tissues and amniotic fluid, they seemed a lot different from what they had been, and were thus “changed” and unfamiliar even though they were the same words? Or, perhaps, did the mothers who were reading “to their babies” speak differently than those who were reading for a recording?
In a recent study by Christine Moon, Hugo Lagercrantz, and Patricia Kuhl (Moon, C., Lagercrantz, H., Kuhl, P.K. (2013). Language experienced in utero affects vowel perception after birth: A two-country study. Acta Paediatrica. doi: 10.1111/apa.12098), babies born in the United States and babies born in Sweden were compared to see whether they preferred (i.e., sucked more in order to hear) vowels characteristic of speech in the U.S. or Swedish vowels. In each country, the newborns were more attentive to the vowels that they had not heard prenatally. Newborns in the U.S. preferred to listen to Swedish vowel sounds, and Swedish babies preferred to listen to U.S. vowels sounds. As we would predict from their tendency to habituate, the babies paid more attention to the unfamiliar than the familiar vowel sounds. These results seem to be at odds with the DeCasper work, unless there’s some explanation like the ones I suggested in the previous paragraph.
To understand how infants’ mental abilities develop, it’s really important to know what can happen before birth, but at the same time to be aware of what probably does not happen until later. It’s also critical to remember that although great minds may think alike, newborns and older individuals don’t necessarily do so. The Internet abounds with comments from people who want to interpret young infants’ responses to speech in terms of what adults do or like… for example, suggesting that learning from speech prenatally means that newborns have already established communication with their birth mothers in a sophisticated way.
Interpreting newborn behavior as if it involved the same motivations and abilities as adult actions is sometimes called adultomorphism, a made-up word derived from “anthropomorphism” (acting as if animals have the same intentions and motives as humans). One highly adultomorphic thought pattern assumes that newborns long for the familiar and feel uncomfortable with the new and unfamiliar, as older children and adults often do. This type of adultomorphism gave rise to the idea that birth is an emotionally traumatic separation from the familiar and comfortable “communion” of fetus with mother-- an idea that is purely speculative, and no more logical than the guess that the child at the time of birth is bored silly and wants to get out and have a look around.
But what infant behavior actually shows us is that for several months after birth babies are fascinated by the unfamiliar. For several months after that, they remain cordially responsive to friendly new people and interesting new situations. By the seventh or eighth month, they start to be wary of new people and things, and take a while to warm up to them. After eight or nine months – when attachment becomes evident in most babies-- they may be frankly frightened of new people and things, avoid them, and come to terms with them best when encouraged and supported by familiar caregivers in a familiar place. Strange though this behavior may seem to the inexperienced observer, in fact the baby is now much more like an adult than he or she was at birth. Like us, older babies are most likely to pay most attention to familiar sights and sounds and to learn from them. Just try changing The Cat in the Hat to The Dog in the Fog and you’ll see what I mean.