Tuesday, September 12, 2006

Subperceptual VOT Effects and Universal Phonemes

A sort of odd subject came up in Bilingualism today: that of sub-perceptual VOT effects in bilingual children.

I have posted before on the Unitary Language Hypothesis: the idea that children exposed to two languages from birth pass through some phase where they are unaware, or at least make no internal distinction between, the two languages. Though this seems intuitive, empirical evidence doesn't necessarily bear it out. Certainly the professor in this course doesn't seem to believe in it.

However, today we got a tiny bit of evidence that might back it up. I don't have a specific reference (though this one from a simple Google search seems as good as any), but the idea was that Voice Onset Time is different between bilinguals and monolinguals at a sub-perceptual level.

In other words, there are differences - subtle to the point that normal listeners can't hear them, but present on any accoustical measure - between the way bilinguals pronounce their words and the way monolinguals pronounce them. Though it sounds like a purely bilingual child has a "perfect" accent, on the level of the sound wave, it seems that the child has actually cut a corner or two.

As a concrete example: Spanish and English speakers don't pronounce /p/ the same way. Though on some intuitive level we understand that what we hear is "a /p/," we can also hear a difference in the way it's pronounced. This is why it's meaningful to say things like "it's a Spanish /p/."

Well, given a child raised speaking both English and Spanish at home, what the research apparently shows is that such a child will pronounce its English /p/s like English /p/s for the most part (remember, supposedly people can't actually perceive the difference just by listening - it takes electronic equipment to record it) - only they will be slightly "more Spanish" than those for a monolingual English speaker. Likewise, when speaking Spanish, the child will pronounce its /p/s like everyone else as far as its family is concerned, only they will be slightly "more English" than those of monolingual Spanish speakers.

Now, this isn't exactly slam-dunk evidence for the Unitary Language Hypothesis, I realize that (though it is perhaps suggestive). But it is potentially evidence for something more interesting: the reality of language-independent phonemic categories. There is some level at which the child is storing its two /p/s in a similar place. We know this because they affect each other. If these two categories were truly language-independent, what we would expect to see, I would imagine, is phonemes that pattern exactly as they do for monolingual speakers. Instead, there is (admittedly minimal) overlap.

It will be objected by people (like this guy) who reject a phonemic level of representation (or used to, or do on Tuesdays except during Passover, or something - it's not terribly clear) that this is an artefact of pronouncing the two sounds in similar locations repeatedly. Motor memory stores exemplars of past productions, and these end up interfering with each other. As to the question of how the subject manages to continue to differentiate between the two distinct (realizations of) phonemic categories in the distinct languges, they would presumably say that this comes from associations with the other serial sounds being produced. The similarity in VOT is an articulatory effect - but only one of many, the others being effects that come from repeatedly producing series of sounds in the given language category.

Yes, but that's dodging the question in a sense. The point is that Spanish and English have this sound that is pronounced in similar enough ways that the subject becomes at least a little confused as to which is which. The two categories do exhibit an influence on each other, and they do so because they are similar across the two languages in some important sense.

If, indeed, there are language-universal phonemic categories that are defined with respect to things in addition to articulation, we should expect to see effects here that cannot be predicted by articulation alone. That would indeed be very interesting.

I am not a phonetician, so that's about as far as I can speculate about this stuff - but it seems like an interesting topic with potential consequences for the nativism debate.

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