Kathleen Currie Hall

Notes on: Edwards, Jan, Fiona Gibbon, and Marios Fourakis. 1997. On discrete changes in the acquisition of the alveolar/velar stop consonant contrast. Language and Speech, 40(2): 203-210.

Summary:
In this article, the authors respond to a previous article by Thomas Berg, which traced the acquisition of velar stops in word-initial position of a single child.  While they praise his work and his large corpus, and especially his conclusion that acquisition was gradual and not abrupt, they disagree with his conclusion about _why_ this acquisition is gradual, claiming that it is a matter of gradual motor control rather than gradual psychological realization.  

Details:
1. Berg claims that features and phoneme segments are "connected" and that the connection between these two is built up gradually over time -- hence gradual acquisition of velar stops, for example.
2. Edwards, Gibbon, and Fourakis claim that "features" and "phonemes" are only abstract representations and that the "acquisition" of an abstract concept like "velar" involves the acquisition of _many_ motor skills (since "velar" may differ depending on e.g. following context).
3. Therefore, they claim that the source of gradual learning is simply the gradual nature of learning motor control.  
4. They argue that motor control can be shown to be gradual through the existence of covert contrasts: i.e., that there is clearly not a categorical jump between a single, undifferentiated motor gesture and a pair of fully adult-like motor gestures.  
5. The rest of the paper largely covers the basics of covert contrast and shows examples of it.
6. A final point is that linguists need to be careful in terms of using transcriptions when the whole point of covert contrast is that it is covert . . . .

Questions:
1. I'm not sure I know why Berg's explanantion is completely incompatible with that of Edwards, Gibbon, and Fourakis (perhaps because I haven't read his paper?).  Is it the case, in cases of covert contrast, that there is generally a tendency to differentiate, or that there is usually a reliable way to differentiate a child's productions, but one that is not detectable to adult ears (e.g. in the EPG data, it looks like I could definitively categorize all the productions of [d] and [g])?  If the latter, then there is a sense in which each stage along the gradient path from one undifferentiated gesture to two adult gestures is categorical.  It doesn't seem impossible to me that a child could have good control over these categorical gestures, perhaps being able to differentiate his own productions as clearly as if they were adult-like, but that in another context, he doesn't know that he should be producing the _same_ contrast (even though he could in theory be producing a different covert contrast).  Hence it could be only gradual that the child realizes that the sounds in these two contexts are in fact both "velar" (precisely because it is an abstraction) and begins producing them the same way.  (Note that even if the child doesn't have good motor control over the covert contrast, this idea could still work -- i.e., it could be BOTH a case of immature motor control AND a lack of strong psychological connection between an abstract feature and a set of sounds.)  
2. Could we go over the definitions of the various "spectral moments" they use here?