How do we change our voices when we talk to babies?

Elise Piazza and her colleagues research “motherese,” better known as baby talk.

Vocabulary: timbre, tone color, pitch, rhythm, sound wave

Next Generation Science Standards:PS4.A: Wave Properties, SEP3: Planning and Carrying Out Investigations, SEP2: Developing and Using Models, CCC1: Patterns.


Credit: Shutterstock

Researchers have known for a while that parents change the pitch of their speech when talking to their infants, often producing the sing-song cadence we have defined as “baby talk.” But new research published in the journal Current Biology this week suggests that there’s something else adults are doing when they use this special form of communication with their baby — they are changing the timbre of their voice.

Timbre is an important feature of sound that helps us identify different musical instruments and distinguish idiosyncratic voices. “For instance if you heard Gilbert Gottfried and Barry White singing the same note or the same pitch even with the same rhythm you would still be able to tell them apart very easily,” says Elise Piazza, a neuroscientist at Princeton University and co-author of the study. “That’s because they have these idiosyncratic timbres that distinguish them.”

Piazza and her colleagues found that mothers tend to make adjustments to the timbre of their voice while speaking to infants that they don’t make when talking to other adults. The change was even detected in other languages in addition to English. Like pitch, timbre changes are likely giving infants important information about the structure of speech. Dr. Piazza joins guest host John Dankosky for a brief lesson on the language of “baby talk.”

Audio Excerpt “A Lesson In The Language Of ‘Baby Talk’,” Oct. 13, 2017. (Original Segment)

Print this segment transcript.


  • How do you think researchers figured out that babies prefer it when we use a higher pitch?
  • Do you think that timbre plays into recognition of caregivers by babies?
  • Why do you think that similar timbre patterns exist across the languages surveyed?
  • Do you think that humans are the only animals that use “motherese” or infant-directed speech? How might you see if this type of vocal pattern extends beyond humans?
  • Timbre is also known as tone color. When thinking about sound waves, why might color be a good descriptor?
  • Elise Piazza mentions different timbre descriptions including reedy, buzzy, mellow, nasal, velvety. These all seem similar to textures. Create a chart of singers or actors and timbre descriptions you think fit with their voices.

Activity Suggestions

  • Using this activity on the Bouba-Kiki Effect to have your students look at the roots of our words. The Bouba-Kiki effect describes the tendency of people to identify certain sounds with specific types of shape. Have your students test out the Bouba-Kiki Effect, learn about current research, create their own sound-shape pairings based on the theories behind the Bouba-Kiki effect, and evaluate different explanations for the effect based on their observations.
  • Have students investigate the sounds of humans. Explore the field of bioacoustics with this activity where students record and analyze the sound waves of human burps. After they are more familiar with the program, have them use the baby talk segment as inspiration to design an investigation into timbre.
  • Learn more about the way hearing assistive technologies process sound in this activity exploring cochlear implants. Have students learn how hearing aids work, then conduct their own tests to determine whether hearing aids can improve speech recognition for cochlear implant users.

Additional Resources

If you are curious about “the birth of a word,” or study into how children acquire words, check out Deb Roy’s TED talk discussing the influences of caregiver speech on word acquisition.