Tuesday, October 12, 2010

Japanese infants hear sounds based on native language by 14 months

Japanese infants, by the time they are 14 months old, are believed to have tuned their perception to how sounds are sequenced in their native language even before learning its words and grammar, the Riken Brain Science Institute said Tuesday in a report on its joint studies with a French laboratory.
Involving 24 8-month-old Japanese and French infants each and as many 14 months old, the joint study found that only 14-month-old Japanese infants were unable to distinguish words with sound sequences foreign to the Japanese ear, Riken said.

The question of how infants learn to perceive and segment speech is central to the understanding of the origins and development of language, according to Riken.

Studies have shown that young infants can already distinguish patterns common to their language from those that are not, but it is not clear how the capacity relates to the highly tuned perception of speech known to occur in adults.

One way to explore the connection is through the phenomenon of ‘‘phonological illusions,’’ in which adults hear sound sequences from a foreign language as if they were ‘‘repaired’’ to fit their native tongue, Riken said.
To determine at what age such illusions first develop, the joint study tested the ability of Japanese and French infants at 8 and 14 months of age to distinguish series of utterance pairs such as ‘‘abna’’ and ‘‘abuna,’’ only the latter of which is pronounceable in Japanese.

Earlier research by the team had shown that adult Japanese perceive such utterances as the same, inserting an illusory vowel ‘‘u’’ between the cluster of consonants, Riken said. The current experiments show that while at 8 months of age, the phenomenon does not yet occur in either group, by 14 months a clear difference emerges—Japanese infants, unlike French infants, no longer perceive the distinction between these utterances unless they are presented to them in isolation.

In the Japanese language, all words are composed of either vowels only or combinations of consonants and vowels. Words that have a succession of consonants exist in the French language, but not in Japanese.

‘‘It has been thought that this repairing ability is acquired by adults after they learn many words. It is amazing that infants already hear sounds in a similar way to how adults do,’’ said Reiko Mazuka, who led Riken’s team in the study.

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