Kathleen Currie Hall

Notes on Baum, Shari R., and James C. McNutt. 1990. An acoustic analysis of frontal misarticulation of /s/ in children. Journal of Phonetics, 18: 51-63.

Summary
This paper discusses the results of a production study of /s/ and /theta/ articulation for both normal children and those who produce fronted /s/.  It is found that contrary to popular conception, fronted /s/ is not always /theta/; there are consistent differences between /s/ and /theta/ in productions of children with frontal misarticulation.  There is evidence that children who have frontal misarticulation are simply developmentally delayed, as older children with misarticulation corresponded well with younger normal children.

Details
1. Four groups: 5-6 year olds with normal /s/; 5-6 year olds with fronted /s/; 7-8 year olds with normal /s/; 7-8 year olds with fronted /s/
2. Task: repeat stimuli of the form /sVt/ or /TVt/.
3. Measures: Duration.  All groups had longer /s/ than /T/ on average.  More consistent with normal children.  Misarticulating children tended to have longer /T/ duration than expected -- so their /T/ sounds more /s/-like rather than vice versa.  Movre variability among misarticulating children.
4. Measures: Amplitude.  All groups had lower amplitude /T/ than /s/ on average.  Variability was same across all groups.  Perhaps this is the most salient distinction between /s/ and /T/ and so is most accurate among misarticulators?
5. Measures: Spectral frequency.  All groups had higher centroid frequency for /s/ than /T/.  Not true across all individuals -- perhaps some of the misarticulators have only a single representation for /s/ and /T/? Misarticulators tend to have lower frequencies for /s/ than do normal children; this is probably the source of the label "frontal misarticulation."
6. Older children were less variable than younger children.  Older misarticulatos tended to behave like younger normal speakers, suggesting that frontal misarticulation is simply developmental delay.
7. "Frontal misarticulation of /s/" is clearly not a single factor.  It is not clear, however, if it is due to fuzzy mental representations of /s/ vs. /T/ or articulatory inability.

Questions
1. I wonder if perceptually all the "frontal misarticulators" sounded the same to the testers, or whether the measures on the screening test were taken objectively, with no sense of where the problem actually lies for each child.
2. Would lexical information play a role?  For example, would "thought" vs. "sought" make children show more of a difference than "seat" vs. "theat"?  Was there an effect of vowel quality?
3. Did the stimuli vary in terms of vowels only within each pair presented, or were /s/ and /T/ contrasted in presentation?
4. Why were tokens without release of the final stop excluded?  How many did this involve?
5. What exactly is average intra-speaker standard deviation?  Why is there only one value for each group?