A pregnant belly is hard to resist, whether it's our own or someone else's…we all want to talk to it, read to it and sing to it. It's natural and fun and just can't be helped! But what are those little bundles of joy actually listening to and how do we know? Unlike the visual system, which begins to develop at birth, hearing begins at approximately 27 weeks gestational age, or the onset of the third trimester of pregnancy.
In 1980 researchers from North Carolina published a study that used a technology called the nonnutritive sucking paradigm to determine whether newborns had learned their own mother's voice during that last trimester in the womb. They asked a group of mothers to read the same Dr. Seuss story, and then they presented these stories to their 1- to 3-day-old infants. They gave the newborns specialized pacifiers wired to computers that controlled the sounds that came out of the nearby loudspeakers. The researchers measured the newborns' baseline levels of sucking on these pacifiers and then played their own mother's voice when the newborns sucked the pacifiers at greater rates than baseline. If the newborns sucked at baseline or lower, they heard another mother's voice. Even though they were listening to the exact same story and had very little postnatal contact with their mothers, the brand new babies sucked the pacifiers faster to hear their own mother's voice rather than another mother's voice. This meant that these newborns had learned their mother's voice while in the womb. Other researchers have used this technology to determine that newborns have also already learned to distinguish the sounds of their native language, and even vowels from their language, from those of other languages.
These findings made researchers excited about discovering more about the auditory learning that happens during that last trimester. Luckily, around this time other scientists found that infants' and fetuses' heart rates slow down when they experience something that interests them. Auditory researchers used heart rate monitoring technology to explore listening and learning in the womb, and found that fetuses' heart rates slow down when listening to speech sounds, and, in particular, their own mother's speech. Recent research has also shown development from simple awareness of music to active attending to music, as shown by heart rate acceleration and deceleration patterns in the last trimester.
Some researchers have also used these types of findings to train fetuses on listening tasks while in the womb, and then testing them shortly after birth to see if they learned the particular sounds. In one such study that was published just last fall, researchers from Finland found that newborns could distinguish between a musical tune they heard in the womb during the last trimester from one they hadn't heard.
These studies are fascinating, especially if you or your spouse is about to enter that last trimester! But before you run out and buy yourselves some specialized headphones to directly pipe music or foreign languages through your little belly bump (did any of you see the Belly Buds on Modern Family or Keeping up with the Kardashians?), keep in mind that all of these studies were done with either natural speech from mom – simply talking without any amplification or directional microphones – or with recordings from loudspeakers in the natural environment, not some apparatus attached to the belly. Regardless, you don't have to spend the $50-160 on specialized buds to reap the benefits of talking to or playing music for your little one, and you and your spouse might enjoy it more, too, if you can all listen together!
Cognitive psychologist Tonya Bergeson-Dana combines her real world experience as a mother with her professional training as a researcher to provide parents with a practical way to apply the most current findings in childhood development research to their everyday life. Tonya is also a co-founder of The Urban Chalkboard playcafe, and welcome questions and feedback from readers at firstname.lastname@example.org.