What Newborns Hear and Learn in the Womb

Another experiment, however, proves that babies really do imprint on auditory experiences while still in the womb. In this case, mothers were asked to read a particular story aloud, twice a day, during the last six weeks of pregnancy. The story was by Dr. Seuss again, this time The Cat in the Hat, and it was estimated that the babies spent a total of about five hours listening to it in the womb. Shortly after birth, they were tested to see whether they preferred listening to their mothers read this story or another one. The King, the Mice, and the Cheese. These newborns sucked more to hear The Cat in the Hat, showing that they both remembered and preferred a story they'd heard only in the womb. Still another study showed that newborns prefer the sound of their mother's voice as it is actually heard in the womb—in the same muffled, deeper tones produced by the sound traversing her body (which researchers were able to mimic by filtering out frequencies above 500 Hz)—to the way it sounds outside the womb.

So fetuses not only begin hearing well before birth, what they hear in the womb has a surprisingly large impact on them. In addition to their mother's before birth. One of their favorites is her heartbeat, a steady, comforting companion that they hear from the onset of hearing to the moment of birth. Newborns are known to be calmed by the sound of a maternal heartbeat, and one study even found that repeatedly playing the recording of a mother's heartbeat into the incubators of preterm babies improved their mental development as measured at two years of age.

If babies can remember The Cat in the Hat after several repetitions in utero, it is easy to imagine other familiar sounds they develop a liking for— a lullaby sung every night to an older child, a currently popular song on the radio, or (as in the case of my second baby) the fan inside a desktop computer. One British researcher found that newborns whose mothers watched a particular soap opera during pregnancy stopped crying when they heard the show's theme song, whereas babies whose mothers hadn't watched the program showed no reaction to the song. Newborns apparently have a keen memory for their prenatal auditory experiences, and hearing those familiar sounds is yet another way of smoothing their transition to postnatal life.

Unfortunately, one stimulus that doesn't appear to register prenatally is Daddy's voice. When tested, newborns have not been found to be capable of recognizing their own father's voice better than that of a strange male. This result is surprising, because as we have already seen, lower tones penetrate the womb better than high ones. It may be that fetuses can't learn their father's voice because it is masked by all of the other loud, low-frequency tones coming from the mother's own body—her heartbeat, blood flow, and stomach rumblings. This masking, together with newborns' strong familiarity with their mother's voice, means that they generally prefer female over male voices, even a strange woman's voice over that of the father.

But fathers need not despair. Within a few weeks of birth, the baby will know and prefer his voice to that of other men. It is also quite possible that if a father made a special effort to speak loudly to his wife's stomach every day over the last month or two of pregnancy, his child would know his voice from the moment of birth. The experiment simply hasn't been done yet.

The mother's voice, stories read to them, and sounds from their environment; with the exception of the father's voice, to which the infant grows habituated very soon after birth.