From birds songs’ to babies’ babble

 

  • New insight into human language development
  • Results revealed of interdisciplinary research by biologists and psychologists

Contacts between researchers from different disciplines can often lead to scientific advances. That is undoubtedly one of the messages from a research report published in the journal Nature and picked up by the New York Times. The research brought together scientists working in the biology and psychology departments of New York City University – some interested in birds and others in the acquisition of human language.

On the face of it there is no similarity between birdsong and the familiar da-da-da, do-do-do babbling of human babies. Nevertheless, the scientists have discovered that birds learn to sing in the same way as babies learn to talk.

The original experiment was on young zebra finches. The scientists placed them in soundproof cages and taught them to repeat tunes, starting with a single melody, composed of three “syllables” (A-B-C). Once the finches had learned this melody, Dr Ofer Tchernichovski and his colleagues whistled another, composed of the same syllables but in a different order (A-C-B). Simple, or so it seems. However, the scientists observed that the young birds had to make considerable efforts in order to master the new melody. They repeated the syllables two at a time, slowly getting closer to the model. This was also true when the scientists introduced a new syllable into the melody. The research conclusion is that the difficulty lies in transitions between different syllables.

Kazuo Okanoya, one of the team of biologists, has observed the same process in Bengalese finches. While their melodies are more complex, they acquire their songs by starting out with combinations of syllables that are much more limited.

The researchers shared their findings with Gary Marcus who studies human language at New York University. The question was whether the difficulties encountered by the birds might also be experienced by human babies. Gary Marcus analyzed recordings of babies’ babble and found that, when they introduce a new syllable into their vocabulary, babies tend first to repeat it (do-do-do), then introduce it either before or after other syllables which they already know (do-da-da-da or da-da-da-do) before finally inserting it in the middle (da-do-da).

Babies do not, therefore, progress in a linear fashion from monosyllables to polysyllabic sequences, but move back and forward between the two. According to the researchers, mastery of these transitions represents the critical point which allows human beings to progress from babble to language. The long interval between babies’ abilities to understand language and to speak it could be due at least in part to the fact that the process of learning the transitions is so complex.

VIOLAINE JADOUL

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