To learn a language is to learn a set of all-purpose rules that can be used in an infinite number of ways. A new study shows that by the age of seven months, human infants are on the lookout for abstract rules – and that they know the best place to look for such abstractions is in human speech.

In a series of experiments appearing in the May issue of Psychological Science, a journal of the Association for Psychological Science, Gary Marcus and co-authors Keith Fernandes and Scott Johnson at New York University exposed infants to algebraically structured sequences that consisted of either speech syllables or non-speech sounds.

Once infants became familiar with these sequences, researchers presented the infants four new unique sequences: Two of these new sequences were consistent with the familiarization “grammar,” while two were inconsistent. (For example, given familiarization with la ta ta, ge lai lai, consistent test sentences would include wo fe fe and de ko ko (ABB), while inconsistent sentences would include wo wo fe and de de ko (AAB). Marcus and his colleagues then measured how long infants attended to each sequence in order to determine whether they recognized the previously learned grammar.

In the first two experiments, the researchers examined infants’ rule learning using sequences of tones, sung syllables, musical instruments of varying timbres and animal noises.

Across both experiments, infants were able to identify rules only when exposed to speech sequences (versus non-speech sequences). These findings are significant, says Marcus, because “the essence of language is learning rules, and these results suggest that young infants are specifically prepared to learn these rules from speech.

In the third experiment, the researchers discovered another intriguing result: Infants were able to generalize rules found in speech to sequences of non-speech sounds, even though they could not directly learn rules from the non-speech sequence.

Infants were then re-familiarized with structured sequences of speech and then tested on their ability to discriminate those same structures in tones, timbres, and animal sounds. Infants who received exposure to structured sequences of speech were able to recognize these same structures in the nonlinguistic stimuli. This shows, according to Marcus, that “infants’ drive to understand the abstract patterns underlying speech must be much stronger than their pull towards understanding abstraction in other domains”

“Infants may analyze speech more deeply than other signals because it is inherently capable of bearing meaning, or because it bears some not-yet-identified acoustic property that draws the attention of the rule-induction system” writes Marcus.

“Regardless, from birth, infants prefer listening to speech,” he continues, “and the intriguing patterns we have observed in rule learning and transfer could in some way be an extension of that initial, profound interest in speech.”

Source: APS

Full “Infant Rule Learning Facilitated by Speech” report attached.