Hyperarticulated productions of /r/

In order to compare non-hyperarticulated with hyperarticulatedproductions of /r/, all /r/

tokens produced after the first recognition error made by the simulated ‘silent speech’ reader were coded as hyperarticulated. Productions made prior to the initial computer error in the ‘silent speech’ (non-hyperarticulated) session were therefore not included. All nine /r/-initial words produced in the session in which the computer made no recognition errors were considered to be non-hyperarticulated. For statistical analysis, the dichotomous tongue shapes for/r/(i.e., bunchedandretroflex) will be considered rather than the five configurations to increase experimental power.

Modifications to tongue shape

To assess changes in tongue shape from non-hyperarticulated to hyperarticulated/r/ pro-ductions, the five tongue configurations were transformed into a numeric scale from zero to four with zero being the mostbunched(Mid Bunched) and four being the mostretroflex

(Curled Up). The mean tongue shape was then calculated for each speaker according to context (non-hyperarticulated andhyperarticulated). The resulting means were then transformed into a percentage by multiplying by 25. We consider this percentage to correspond to a measure of the rate ofretroflexion: a speaker who only produces the most extreme Curled Up (CU) shape would obtain a value of 100%, while a speaker who exclusively uses the mostbunchedMid Bunched (MB) shape would obtain 0%. As previously discussed, the Front Up (FU) shape is considered to lie in the middle of the retroflex-bunched continuum. As a result, a speaker who obtains 50%retroflexion produces Front Up configurations exclusively. Rate ofretroflexion in thehyperarticulationcontext increased in 10 of the 14 exclusivelyretroflexusers. In the remaining 4retroflexusers, rate ofretroflexionremained the same, although one speaker had already obtained aretroflexionrate of 100% in the non-hyperarticulated context. In 5 out of the 7 bunchers, rate of retroflexion did not change inhyperarticulation. In the remaining 2 bunchers, retroflexion decreased, in other words, bunching increased. In the 3 speakers who present bothbunchedandretroflextongue shapes,retroflexionincreased in one, while bunchingincreased in 2.Figure 4.23shows the mean percentage change inretroflexionfrom non-hyperarticulated tohyperarticulated/r/productions for each speaker. The colours corre-spond to the tongue shape or shapes the speakers were coded to use, i.e.,retroflex,retroflex andbunched, orbunched. These results indicate that although 9 speakers present no change in tongue shape, the remaining 15 use more ‘extreme’ tongue shapes inhyperarticulation. Three of the nine speakers who showed no change already produced the most extremebunchedor retroflextongue shapes in the non-hyperarticulated context across the board. In speakers who showed a change in thehyperarticulatedcontext, exclusivelyretroflex users produce more retroflexion, exclusivebunchers produce morebunchedshapes and speakers who use both retroflexandbunchedshapes presented either moreretroflexor morebunchedshapes.

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Figure 4.23:Percentage of retroflexion in non-hyperarticulated and hyperarticulated productions of/r/for each speaker. Colours indicate the shape of the tongue.

We predicted that a possiblehyperarticulationstrategy inretroflexusers could be the use of moreretroflexion, in order to increase the size of thesublingual spaceand lower F3. Using the same technique as inSection 4.3.1, the proportion of each of the five tongue configurations was plotted as a function of the following vowel for both non-hyperarticulated andhyperarticulated productions of /r/ in speakers who use at least one of the three retroflex configurations (n=17). The results are presented inFigure 4.24. Although the left non-hyperarticulated plot is identical to the one presented inFigure 4.14, for ease of comparison, it has been presented again here. We generally observe a higher proportion of the Curled Up (CU) configuration in thehyperarticulatedcontext, although the proportion of CU is smaller in the context of the lot vowel (76.5% non-hyperarticulated versus 70.6%hyperarticulated). The largest proportional increases inretroflexionoccur for/r/following the vowels trap, fleece, goose, dress. While the latter three were the vowel contexts in which the simulated ‘silent speech’ programme made recognition errors (i.e., in the wordsreed, red, room), these results indicate thathyperarticulation was generalised to all productions of/r/even when the computer did not make errors. /r/

followed by the trap vowel had the largest proportional increase in extremeretroflexiondue tohyperarticulation.

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Figure 4.24:Proportion of tongue configurations as a function of the following vowel produced in retroflex users in non-hyperarticulated and hyperarticulated/r/.

Although tongue shape variation may in some cases be due to coarticulation with the neighbouring vowel, two speakers (14, 18) who use bothretroflexandbunchedshapes switched from one shape to the other inhyperarticulated/r/in the same vowel context. Figure 4.25 presents ultrasound images of the wordreed produced by speaker 18. While in her non-hyper-articulated production,/r/was produced with a Front Bunched (FB) configuration,/r/became moreretroflexin speech repairs directly following ‘w’ recognition errors. The first repetition after the misrecognition was produced with a Front Up configuration. She then produced a more extreme Tip Up shape when the computer mistook her/r/production for ‘w’ for a second time. Interestingly, she retained her usual FB shape for the/r/inreed when she was presented with ‘lead’ as the computer’s feedback response. We note that as only one repetition was recorded per word in the non-hyperarticulated context, we cannot be sure that she habitually uses a bunched configuration in the context of the fleece vowel. We did however record another word containing the same fleece vowel,reap, which speaker 18 also produced with the same Front Bunched tongue shape.

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Figure 4.25:Ultrasound tongue images from Speaker 18’s productions of the word reedwhich was produced with multiple tongue configurations (FB, F U, TU) with hyperarticulation. The

tongue tip is on the right.

Lip protrusion

The results from non-hyperarticulated/r/productions indicated that the degree oflip protrusion may be related to tongue shape with bunchedshapes presenting more lip protrusionthan retroflexones. We predicted thathyperarticulated/r/will be produced with morelip protrusion than non-hyperarticulated /r/in order to extend the front cavity. While we predicted that retroflexers may further increase the size of the front cavity via more retroflexion, as this strategy is not available to bunchers, bunched /r/ users may present more lip protrusion than retroflexersin the hyperarticulatedcontext. Figure 4.26presents box plots of raw lip protrusionvalues (in mm) forbunchedandretroflextongue shapes according to context (non-hyperarticulated versushyperarticulated). It suggests that althoughlip protrusionincreases inhyperarticulationacross the board,hyperarticulated bunched/r/is produced with more lip protrusion than hyperarticulated retroflex /r/. The median value of lip protrusion in hyperarticulated retroflex tokens roughly corresponds to that of the non-hyperarticulated

bunchedones. There are however, a larger number of outliers in theretroflextokens than the bunchedones.

Figure 4.26:Box plots of raw lip protrusion values (in mm) for retroflex and bunched/r/

according to context (non-hyperarticulated versus hyperarticulated).

Figure 4.27presents meanlip protrusionvalues for/r/produced in non-hyperarticulated andhyperarticulatedspeech in each speaker. The speakers are ordered from mostbunched to mostretroflex. In the vast majority of speakers,lip protrusionincreases on average in the hyperarticulatedcontext. The most substantial increases seem to occur in the first few speakers presented in the graph, i.e., in the speakers who only presentbunchedtongue shapes. Increased lip protrusion is particularly evident in speakers 17 and 10 both of whom use exclusively bunchedtongue shapes.

If hyperarticulation is targeted in order to increase the phonetic distance between the cues distinguishing the target from the competitor, we may observe different degrees oflip protrusionaccording to the labial features of the competitor. We elicitedhyperarticulation by simulating computer recognition errors where word-initial/r/was recognised as either

‘l’ or ‘w’ in the programme’s text feedback response. It could be argued that increasing the

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Figure 4.27:Mean lip protrusion (in mm) per speaker according to context (non-hyperarticulated versus hyperarticulated). Speakers are ordered from most bunched to most retroflex.

degree oflip protrusionfor/r/when placed in direct competition with/w/, which is produced withlabialisation, would actually decrease the phonetic distance between the target and the competitor. Whereas, unlike /w/, as /l/ is not produced with labialisation(at least word-initially),lip protrusionfor/r/would increase the/r/-/l/contrast.Figure 4.28presents raw lip protrusionvalues in both non-hyperarticulated and hyperarticulatedproductions of /r/

according to tongue shape (retroflexorbunched). Hyperarticulated productions were divided into the following three sub-categories:

Initial hyper: initial production of target words

/w/competitor: speech repairs directly following a recognition error of ‘w’

/l/competitor: speech repairs directly following a recognition error of ‘l’

The box plots suggest very little difference in the degree oflip protrusionbetween /r/

productions correcting ‘l’ misrecognitions and those correcting ‘w’ misrecognitions, regardless of tongue shape. We decided not to run statistical analysis comparing the degree oflip protrusion for/r/between/w/and/l/competitors because there was not enough data to do so with any experimental power (n=268) and because the box plots show little evidence to suggest a robust difference. The box plots also indicate that the degree oflip protrusiondoes not greatly differ between the initial productions of target words in thehyperarticulationsession and the speech repairs directly following a recognition error, indicating thathyperarticulationwas targeted to/r/productions across the entire session. This is perhaps not surprising given the fact that misrecognitions were never followed by more than four correct recognitions of/r/across the hyperarticulatedsession (following the results from Stent et al., 2008). As a consequence, all productions of/r/in thehyperarticulationsession will be pooled in subsequent analyses to increase experimental power.

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Figure 4.28: Box plots of raw lip protrusion values (in mm) for/r/according to tongue shape and context including competitor information.

Acoustics

It was predicted thathyperarticulationwould result in lower F3 values than those observed for non-hyperarticulated/r/. The box plots inFigure 4.29show the effect ofhyperarticulationon F3 inbunchedandretroflexshapes in female speakers. The median values do not greatly differ between non-hyperarticulated andhyperarticulatedcontexts in bothbunchedandretroflex /r/, although they do lower ever so slightly inhyperarticulation.

Figure 4.29:Box plots of raw F3 values (in Hz) for bunched and retroflex/r/in women according to context (non-hyperarticulated versus hyperarticulated).

Figure 4.30presents the mean F3 value (in Hz) for all speakers according to context (non-hyperarticulated versus hyperarticulated). Again, speakers have been ordered from most bunchedto mostretroflex. No obvious trends seem to occur with regards to tongue shape. For the majority of speakers (16/24) F3 decreases on average in thehyperarticulatedsession. While in some speakers the decrease in F3 is substantial (i.e., F3 drops by over 250 Hz in Speaker 18), decreases to F3 are much subtler in other speakers, and in eight speakers F3 actually increases on average.

Although no predictions were made regarding F2, for the sake of clarity, we present box

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Figure 4.30:Mean F3 (in Hz) per speaker according to context (non-hyperarticulated versus hyperarticulated). Speakers are ordered from most bunched to most retroflex.

plots for F2 inFigure 4.31. Forretroflextokens, F2 appears to lower inhyperarticulation, while the median F2 value goes up inhyperarticulated bunchedtokens. However, both effects appear small.

Figure 4.31:Box plots of raw F2 values (in Hz) for bunched and retroflex/r/in women according to context (non-hyperarticulated versus hyperarticulated).