From: LAURA SLOCUM This article highlighted results from 1 of 9 subjects who participated in a longitudinal study - the one who failed to contrast voiced and voiceless stops in the word-initial position. Measurable acoustic and articulatory data were utilized in order to support the claim that children mark contrasts in ways imperceptible to their listeners. Therefore, what are commonly characterized as "phonological disorders" in children may represent the listeners' perceived lack of contrast rather than children's impaired phonological systems. The authors note that children's phonetic systems may continue to develop well after their phonological and speech motor systems and this "interface" may account for discrepancies in representation/production/perception discrepancies. From: Kathleen Currie Hall Summary: In this paper, the authors describe the case of a particular 4-year-old who was classified as having phonological disorder (at least partially) because of a lack of voicing contrast in initial stops. They show that in fact, he had a voicing contrast that was signalled by a difference in spectral tilt, and that he used VOT to consistently signal vowel quality. Hence his phonological system was not so much disordered as incompatible with an adult phonetic output system. Details: 1. Covert contrast -- very much key especially in clinical studies; often the case that adult listeners/transcribers may not be able to detect a contrast made by a child until significantly after the child begins to make it, leading to misdiagnosis or mistreatment. 2. In adult speech, spectral tilt (measured here as: dB at the first harmonic minus dB at second harmonic) tends to be greater after an aspirated stop than after an unaspirated one. 3. The child they measured had no audible difference between /t/, /d/, and /st/. There were no significant differences in any of the duration measurements the authors took (including duration of VOT), when measured across following vowel context. 4. The child did produce significantly longer VOT before [i] than before [o], and significantly longer VOT before [o] than before [ae]; this mirrors adult speech where VOT before [i, u] tends to be longer than VOT before [E, a]. 5. The child did produce a significant difference among the spectral tilts of the three onset consonants: /t/ had a much greater spectral tilt than /d/, and /st/ was somewhere in the middle. Questions: 1. It's a bit misleading for the authors to list as many questions as they do in the last paragraph of 13.1 -- clearly, they will not be able to answer all of these questions (especially ones about acquisition timeline and broadly answering questions about the role of VOT in English acquisition) given that they have data from 28 words of one child from one session! 2. I'm surprised they don't make more of the fact that this child (even though "largely unintelligible") did in fact seem to have a good grasp of the adult phonological system in that voicing was cued by spectral tilt and vowel quality was cued by VOT. Given that there _are_ in fact these differences in the adult system, it also seems surprising that more children don't do similar mis-analyses (why are there so many normally developing children?). Are these potential sources of sound change? What prompts the child to figure out the right pattern? 3. Given the discussion on p. 204 about breathy phonation not being a "necessary partner" to aspiration (is this part of the answer to the last question above?), I wonder about the input to this particular child. Presumably he picked up on these cues from somewhere for them to be so regular. What dialect of English do his parents speak (Scottish?)? Is the English in the studies cited British, American, Scottis, Irish? Would these differences make a difference in the child's acquisition? From: ejkong@ling.ohio-state.edu Covert contrast as a stage in the acquisition of phonetics and phonology. - Scobbie and Gibbon It is a case study of DB's stop consonant productions (/t/, /d/ and /st/ before various vowels), which turned out to be covertly contrastive in terms of spectral tilt. The acoustic analysis of VOT and spectral tilt of those consonants indicates that DB's consonantal homophones to the transcriber's ears are phonologically contrastive but the corresponding acoustic cues are not effectively implemented to realize the contrast. From: nagar@ling.ohio-state.edu The study is aimed at describing the importance of covert contrast in acquisition. The authors suggest that the learner, who in this case is a child, is or might be aware of a contrast in phonemes even when it is not manifest in her speech. VOT measures are taken to study the covert contrasts. One child who did not have a voiceless voice contrast was studied and this pronunciations were analysed using durational and spectral analysis. It is discovered that there is a covert contrast that the child makes between consonants. The difference between covert and overt contrast is not as small as it appears, how does a child learn to create overt contrast? In other words, how does covert become overt? Does the child have a meaning disctinction related to sounds evern if she does not produce the contrasts? E.g. would she understnd the difference between ??dog?? and ??tog??? From: Helena Riha p. 194 "... the point at which the child provides useable cues to the contrast for the speech community or transcriber need not be synchronous." It seems that the children in Baum and McNutt's study are forming a covert contrast between /T/ and /s/ that went unnoticed until the researchers conducted an acoustic analysis of the children's productions. p. 198 "Fig. 13.2b illustrates that the initial cycles of phonoation after /st/ and /t/ are relatively sinusoidal compared with /d/. This difference encouraged us ... to measure the spectral tilt immediately following voice onset." What other measurements should be taken to determine children's covert contrasts? Scobbie et al.'s approach seems quite innovative. Are clinicians using more instrumental acoustic and articulatory data to reveal "what the speaker has achieved" (p. 195)? p. 205 "Instrumental analysis of child speech is able to reveal more than covert contrasts -- it provides access to the child's acquisition of individual phonetic skills." Scobbie et al.'s conclusion seems quite bold and unconventional; however, it also assumes that researchers will know what to look for in instrumental analyses to find covert contrasts and that they will also know how to look for relevant characteristics. It seems that considerable training in phonetics is needed for researchers to interpret children's "secret developmental life" in acquiring a phonetic/phonological system. From: Junko Davis Questions: 1. The subject of this study, DB, seems to have undergone speech therapy when he produced the data. I wonder for how long he had received the therapy before the session that this study focused on. I am not quite sure what kind of treatment those phonologically disordered children receive, but could this fact that he has undergone the therapy affect the nature of the study in any way, especially since his /t/, /d/ and /st/ started to be realized in an acceptable manner from the following session? 2. The fact that DB had a covert contrast in word-initial /voice/ is very intriguing despite that he was "largely unintelligible." However, the range of the study is very small (1 subject, 54 tokens). Could this be a general pattern for phonologically disordered children, though? From: ASIMINA SYRIKA -How can you tell a covert contrast from an immature contrast in a child? What criteria do you use for such a distinction and how confident can one be about a classification of this kind? From: Kirk Baker 1. Is a covert contrast perceptible by child producing it? (I guess this is pretty much Laura's question from last time.) Is near merger distinguishable for adult producing it? 2. It seems like everyone knows VOT is the main cue for the 'voicing' distinction in English stops, so why do we still talk about them as if it's a voicing distinction. Why not go ahead and say English has an aspirated-unaspirated stop distinction, and unaspirated stops -> voiced between vowels. 3. To what extent is the VOT difference that is observed for vowels of different heights just an acoustic consequence of vocal tract anatomy vs. something that can be controlled? If it's a physiological constraint, does it count as covert contrast? From: Fangfang Li Summary: in this paper, Sobbie, Gibbon, Hardcastle and Fletcher examined DB's case of his s-stop cluster production. Two acoustic measurements were taken: VOT and H1p value. VOT has been regarded as more perceptual salient and therefore the primary acoustic cue for phonation type for adults and most of the normal developing children. but what they found with DB is that he shows contrast in H1p instead of VOT in differentiating /t/ vs. /d/, while he uses VOT as the primary cue to differentiate rime type instead. their conclusion is that DB apparently is able to produce the contrast and manipulates them using motor control, and what is going wrong is the different mapping between the acoustic cue and the phonemic type that adults have. in other words, his problem does not lie in his disability to either perceive or produce the contrast, but rather in his choice of the wrong acoustic target to approach. questions: 1. in Figure 13.1, covert contrast is described as a necessary stage in language acquisition, which is a too strong claim to me, since covert contrast is mostly attested in developmental-delayed or disordered children, and it needs further evidence to show that it is also a necessary stage for normal-developing children. 2. i wonder how the kid somehow pick the more difficult acoustic parameter as the target and ignore the more salient one? there must be some motivation somewhere. 3. it is interesting that the specific covert contrast they found is not in terms of the different quantity of the same cue (say a marginal differece in VOT), but rather it is in a completely different one, the H1p value. This makes things more complicated. i am wondering what are the things to look at in order to determine whether a child has covert contrast.