Kathleen Currie Hall
9 May 2005

Notes on: Koopmans-van Beinum, Florien J., Clement, Chris J., & van den Dikkenberg-Pot, Ineke. (2001). Babbling and the lack of auditory speech perception: A matter of coordination? Developmental Science, 4(1), 61-70.

Summary:
In this article, the authors attempt to address the question of how much of a role auditory feedback plays in the development of speech production.  Their strategy is to compare the productions of hearing-impaired and normal-hearing infants to determine what type of productions seem to be independent of auditory feedback (i.e., physiological, etc.) and what type seem to require such feedback.

Details:
1. They describe all the productions using a "sensorimotor" classification system, which they claim is independent of any language-specific factors.  Based on the soure-filter theory of speech production, it classifies all productions in terms of phonation type (the source: interrupted or not, varied or not) and articulation type (the filter: none, one articulator, two).

2. They compared five normal-hearing infants and five hearing-impaired infants, using utterances from recordings made by the parents every two weeks or every month for the first two years.

3. They found that NH infants produced more utterances that combined phonation and articulatory movements, while HI infants produced more utterances that just involved phonation, without articulatory movements.  They conclude that the coordination of phonation and articulation is crucially linked with having auditory feedback of one's own productions.

Questions:
1. Can we go over examples of how they would actually implement this language-independent classificatory system?  Does it actually work?  Is it really as easy to implement as they imply?  How reliable is it? etc. . . . (how do they determine presence of articulatory movement in the absence of phonation using just audio recordings?)

2. Relatedly -- what do they mean by determining "syllable structure" or place and manner -- how do they possibly do this in a language-independent way?

3. I know they say that there didn't seem to be an effect of any of the vast differences among the HI infants in terms of hearing aid use or communication type, but this seems implausible.  Is it just the sample size?  How are they really showing anything about the role of auditory feedback if one of the kids didn't use a hearing aid while one had one from the age of 2 months?

4. Relatedly -- the one infant who was hearing impaired but did start babbling at a normal time (7.5 months as opposed to 18 months) -- they say that he "could obviously make use of a hearing residue . . . " (p. 69).  But doesn't this make their argument circular?  There is overall a difference between the NH and the HI kids, which they attribute to auditory feedback.  So when that difference isn't present, clearly there was not a difference in auditory feedback . . . but maybe the original difference wasn't due to auitory feedback in the first place, and their sample is just a fluke (especially since some of the infants had hearing aids and might have had aud. feedback).  I wonder which infant it was that was HI but started babbling "on time" . . . why don't they tell us?