CHAPTER II. SCHWA ALTERNATION: A GRADIENT PHONETIC PROCESS? NEGATIVE
II.2 How similar are clusters in non-schwa variants to identical underlying clusters?
II.2.5 General discussion
The main aim of this study was to determine whether output forms of non-schwa variants show evidence for an underlying schwa vowel. An additional aim was to determine whether pseudowords could be used as a relevant alternative to words in the comparison with schwa clusters. In order to fulfil these aims, we conducted three acoustic analyses comparing clusters in non-schwa variants, identical underlying clusters in words, and identical clusters in pseudowords.
Our comparisons between schwa and underlying clusters in non-schwa words lead to several interesting findings. Firstly, unlike Rialland (1986) and Lebel (1968), we show that cluster duration does not differ between these two cluster types when the variation accounted for by word length, lexical frequency and speech rate is taken into account. According to
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Autosegmental Phonology (Goldsmith, 1976), segments and time are represented on different tiers, each segment being associated with a temporal unit. In many languages, segment deletion leads to compensatory lengthening; the temporal unit left empty is taken by the preceding consonant, and this consonant is lengthened. Our results suggest that the absence of schwa does not lead to compensatory lengthening. Discrepancies between our results and previous studies are likely to be due to two factors. Unlike previous research, our analysis took into account other variables known to influence consonant duration.
Furthermore, we also provided a strict control of cluster position regarding word and syllabic boundaries.
Secondly, we find that acoustical differences between schwa and underlying clusters are rare and not systematic. The automatic analysis suggests that the acoustic distance between the clusters is not affected by cluster type. In the manual acoustic comparison, half the clusters do not differ at all between these two types of cluster. When they do differ, the differences only concern very few acoustic cues. Furthermore, for very few clusters only these differences could be interpreted as residues of a vowel in the schwa condition. In other clusters, they suggest more coarticulation between the two consonants. A possible explanation for this rather complex picture might be that, as shown for cluster duration, other variables affect the acoustic realization of these consonants, such as lexical frequency, word length or speech rate. An additional or alternative explanation is methodological. The fact that we tried so many statistical models (one for each cue of each cluster) drastically increased the probability of a type I error. As a consequence, we cannot exclude the possibility that some of these results are due to chance only.13
Overall, these results suggest that non-schwa variants do not contain acoustic residues of an underlying schwa. This finding makes two accounts of French schwa alternation less likely.
Firstly, it suggests that schwa alternation is not the result of a phonological deletion rule which only partially deletes the schwa, as assumed for instance by Rialland (1986) or Charette (1991). If the schwa was only partially deleted, we would observe residues of this schwa in non-schwa variants’ clusters.
13 In order to avoid type I errors, we could have lowered alpha to 0.01 or 0.001. However, since some predictions involved a lack of difference between the two conditions, doing so would have increased our chances to confirm an hypothesis on the basis of a null result.
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This result also suggests that schwa alternation is not the endpoint of a gradient process of phonetic reduction, as claimed by some authors (Smorodinsky, 1998; Barnes & Kavitskaya, 2002). If schwa was present in the underlying representation of the word and gradually reduced in connected speech, acoustic residues of schwas would be found at least in some occurrences of non-schwa variants. Further research should however investigate whether similar findings are obtained for non-schwa variants produced in more natural conditions, that is, where the speaker is not instructed to produce a non-schwa variant. One could indeed argue that a gradient process of phonetic reduction could lead to realized forms which do not contain any trace of the underlying vowel. This would happen when the reduction process is maximal. Since we explicitly asked our participants not to produce the schwa in the schwa condition, the productions of our speakers could represent the extreme end of this continuous process, and less extreme productions might contain traces of the vowel.
The second comparison of interest concerned clusters in non-schwa variants versus clusters in pseudowords. Again, the three analyses produce convergent results. They all suggest that the two types of clusters are dissimilar. Cluster duration is longer for pseudowords, and the acoustical pattern differs between the two types of clusters, at least for some clusters. This finding suggests that it might not be appropriate to use pseudowords instead of words in the comparison with non schwa variants’ clusters.
To conclude, the main finding of this study is the absence of acoustic residues of an underlying schwa in productions of non-schwa variants. Hence, our analyses do not confirm previous literature suggesting differences between clusters in non-schwa variants and underlying identical clusters. This finding provides empirical evidence concerning the nature and locus of the schwa alternation process. It suggests that schwa alternation is neither the result of an incomplete phonological deletion process, nor the consequence of a gradient phonetic process. Since this conclusion is based on a null result (i.e., the absence of acoustic residues attributable to schwa), positive evidence is now needed to confirm these preliminary findings. In the next chapter, we will look for additional empirical evidence showing that schwa alternation does not result from a phonetic process.
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