Recent research has shown that specific areas of the human brain are activated by speech from the time of birth. However, it is currently unknown whether newborns' brains also encode and remember the sounds of words when processing speech. The present study investigates the type of information that newborns retain when they hear words and the brain structures that support word-sound recognition. Forty-four healthy newborns were tested with the functional near-infrared spectroscopy method to establish their ability to memorize the sound of a word and distinguish it from a phonetically similar one, 2 min after encoding. Right frontal regions—comparable to those activated in adults during retrieval of verbal material—showed a characteristic neural signature of recognition when newborns listened to a test word that had the same vowel of a previously heard word. In contrast, a characteristic novelty response was found when a test word had different vowels than the familiar word, despite having the same consonants. These results indicate that the information carried by vowels is better recognized by newborns than the information carried by consonants. Moreover, these data suggest that right frontal areas may support the recognition of speech sequences from the very first stages of language acquisition.

Significance: It is well known that across languages, certain structures are preferred to others. For example, syllables likeblifare preferred to syllables likebdifandlbif. But whether such regularities reflect strictly historical processes, production pressures, or universal linguistic principles is a matter of much debate. To address this question, we examined whether some precursors of these preferences are already present early in life. The brain responses of newborns show that, despite having little to no linguistic experience, they reacted to syllables likeblif, bdif,andlbifin a manner consistent with adults’ patterns of preferences. We conjecture that this early—possibly universal—bias helps shaping language acquisition.

Two experiments investigated the way acoustic markers of prominence influence the grouping of speech sequences by adults and 7-month-old infants. In the first experiment, adults were familiarized with and asked to memorize sequences of adjacent syllables that alternated in either pitch or duration. During the test phase, participants heard pairs of syllables with constant pitch and duration and were asked whether the syllables had appeared adjacently during familiarization. Adults were better at remembering pairs of syllables that during familiarization had short syllables preceding long syllables, or high-pitched syllables preceding low-pitched syllables. In the second experiment, infants were familiarized and tested with similar stimuli as in the first experiment, and their preference for pairs of syllables was accessed using the head-turn preference paradigm. When familiarized with syllables alternating in pitch, infants showed a preference to listen to pairs of syllables that had high pitch in the first syllable. However, no preference was found when the familiarization stream alternated in duration. It is proposed that these perceptual biases help infants and adults find linguistic units in the continuous speech stream. While the bias for grouping based on pitch appears early in development, biases for durational grouping might rely on more extensive linguistic experience.

The capacity to memorize speech sounds is crucial for language acquisition. Newborn human infants can discriminate phonetic contrasts and extract rhythm, prosodic information, and simple regularities from speech. Yet, there is scarce evidence that infants can recognize common words from the surrounding language before four months of age. We studied one hundred and twelve 1-5 day-old infants, using functional near-infrared spectroscopy (fNIRS). We found that newborns tested with a novel bisyllabic word show greater hemodynamic brain response than newborns tested with a familiar bisyllabic word. We showed that newborns recognize the familiar word after two minutes of silence or after hearing music, but not after hearing a different word. The data show that retroactive interference is an important cause of forgetting in the early stages of language acquisition. Moreover, because neonates forget words in the presence of some –but not all– sounds, the results indicate that the interference phenomenon that causes forgetting is selective.