Infant Speech Perception: You Don’t Want this Kid in Your Phonetics Class

Blog #8 in the Phonology Means Nothing and Other Astounding and Very Practical Facts about Speech Sound Disorders Blog Series

For more information about this series, see the Phonology Means Nothing Series welcome page

By Ken Bleile, PhD
September 18, 2020

Because an infant cannot know beforehand which language they must learn, a child is born able to learn any language. This means, for example, that an infant who grows up learning English also can learn approximately 7,099 other languages ( Speech perception offers a good example of the power of infant learning.

Speech Perception

You don’t want a newborn in your phonetics class, if it is graded on a curve. The world’s languages contain approximately 600 different consonants and 200 different vowels (Ladefoged, 2001), and an infant is born potentially able to hear all of them. Development of speech perception in infants largely consists of fine-tuning a child’s wide abilities in speech perception to fit the specific sounds in the language of the community (Kuhl, 2004; Vihman, 1996). In the first year of life, major perceptual developments occur in intonation and speech sounds.


An infant’s education in speech begins before birth while floating in the womb and hearing the mother’s voice as she speaks. Do you remember that swimming pool game in which children speak to each other under water? That may be like what an unborn child hears when their mother speaks: mostly intonation, very little information about consonants and vowels.

I Know That Voice

Researchers know that an unborn infant hears the mother’s voice because a newborn will turn toward a recording of her voice when it plays from a speaker on one side while another’s voice plays on the other side (Mehler, Bertoncini, & Barriere, 1978). Such recognition may foster bonding between infant and parent early in life when a child is maximally dependent on others to survive.


Infants continue to pay attention to intonation as they grow. At 3 months, an infant may imitate the intonation contour of a caregiver (Gratier & Devouche, 2011). Throughout infancy, intonation helps a child communicate even when the meaning of words is unclear. To illustrate, near 6 months, a child may stop an activity when a parent says “no” in a commanding voice (Hedrick, Prather, & Tobin, 1984). Parents often assume this shows a child understands no and, by ceasing the action, is demonstrating compliance. However, compliance is based on intonation rather than knowing what no means. It’s too perverse to recommend, but if parents wished they could change no to yes (or to dog or bus, for that matter), maintaining a commanding voice, a 6-month-old child would likely respond as if “no” were spoken.

Speech Sounds

To acquire a language, an infant must discover individual sounds buried in the rapid flow of speech—not an easy task, since people seldom speak sounds in isolation, sounds change in pronunciation depending on syllable position and presence of adjoining sounds, and people speak at rates of nine or more sounds per second. Finding speech sounds would probably be impossible were it not for an infant’s mammalian heritage, which includes possessing a cochlea and hearing mechanism capable of categorical perception—that is, able to divide the speech stream into individual sounds (Jusczyk, 1992; Werker & Hensch, 2015).


Categorical perception exists at birth, dividing the flow of speech. When tested in the weeks following delivery, an infant’s perception of speech sounds in the ambient language is the same as their perception of speech sounds in other languages. During infancy, experience shapes a child’s speech perception abilities, and by the first birthday, a child has superior perception for sounds in the language spoken in the community compared to those in other languages (Kuhl, 2010; Zhang & Merzenich, 2001). In Kuhl’s fine phrase, during infancy a child moves from “a citizen of the world” to a citizen of a specific language. The presumed neurological basis of this change in speech perception is maturation of the primary auditory cortex, which is a sensory area adjacent to Wernicke’s area in the temporal lobe (Pascallis, de Hann, & Nelson, 2002).

Keeping What an Infant Started With

Can an infant retain the wide perceptual abilities it began with at birth? Not really—in the case of speech perception, loss of ability means an infant is learning, which is exactly what we want. However, a bilingual infant retains the perceptual categories of the languages to which it is exposed. There even is some evidence that an infant with a babysitter who speaks another language retains the perceptual categories of the babysitter’s language (Zhao & Kuhl, 2016). Importantly, exposure to electronic teachers such as audio and videotapes does not show the same results (Kuhl, 2007, 2010). An infant appears to need interactions with a real person to learn and does not benefit in this area from tapes that do not alter and adjust in response to the child.


Gratier, M., & Devouche, E. (2011). Imitation and repetition of prosodic contour in vocal interaction at 3 months. Developmental Psychology, 47, 67–76.

Hedrick, D., Prather, E., & Tobin, A. (1984). Sequenced Inventory of Communication Development-R. Seattle: University of Washington Press.

Jusczyk, P. (1992). Developing phonological categories from the speech signal. In C. Ferguson, L. Menn, & C. Stoel-Gammon (Eds.), Phonological development: Models research, implications. Timonium, MD: York Press.

Kuhl, P. (2004). Early language acquisition: Cracking the speech code. Nature Reviews: Neuroscience, 5, 831–843.

Kuhl, P. (2007). Is speech learning ‘gated’ by the social brain? Developmental Science, 10, 110–120.

Kuhl, P. (2010). Brain mechanisms in early language acquisition. Neuron, 67, 713–727.

Ladefoged, P. (2001). Vowels and consonants. Cambridge, MA: Blackwell.

Mehler J., Bertoncini J., & Barriere M. (1978). Infant recognition of mother's voice. Perception, 7, 491–497.

Pascallis, O., de Haan, M., & Nelson, C. (2002). Is face processing species specific during the first year of life? Science, 296, 1321–1323.

Vihman, M. (1996). Phonological development: The origins of language in the child. Cambridge, MA: Blackwell.

Werker, J., & Hensch, T. (2015). Critical periods in speech perception: New directions. Annual Review of Psychology, 66, 173–196.

Zhang, L., & Merzenich, M. (2001). Persistent and specific influences of early acoustic environments on primary auditory cortex. Nature Neuroscience, 4, 1123–1130.

Zhao, T., & Kuhl, P. (2016). Effects of enriched auditory experience on infants’ speech perception during the first year of life. Prospects, 46, 235–247.