Pomalatest

Gestural Reduction in Cantonese Production of English Consonant Clusters INTRODUCTION Cantonese learners of English were found to have non-native like realizations of English, and some even persisted for experienced speakers. One of such realizations was that words containing initial consonant clusters (bread, train, and greet) were often mispronounced. Two types of errors, deletion and substitution existed in their production. For example, presentation was often pronounced as [pɪzen’teɪʃn], where [r] is deleted; cry was pronounced as [kwaɪ], where [r] is substituted by [w].

Although many studies had recorded such instances in form of pedagogical reference, the phenomenon was not very well-studied by acoustic analysis. Therefore, the exact quality of these L2 sounds were not known to ensure the mapping of L1 to L2 sounds. Also, few studies investigated this problem through a category-mapping perspective, which involves both phonetic and phonological levels. This provoked us to ask a related question: did speakers rely solely on the L1 candidates to map on L2 sounds, or did any other factor affect their production? In the present article, we aims to investigate if second language sounds are acquired through category formation of L1 only, or also through phonetic reduction. This was examined by a production experiment exploring the nature of Cantonese realizations of English initial clusters.

The paper is structured as follows: (a) a literature review on the phonological cause of non-native realizations of English cluster and previous studies on clusters; (b) participants, stimuli and procedure of the experiment; (c) results of acoustic comparisons by speakers, consonant and vowels; (d) discussions on the nature of the realizations and implications on second language speech acquisition models; (e) conclusions.

REVIEW OF LITERATURE Cantonese vs. English: Consonants and Syllable Structure Cantonese consonant inventory includes voiceless and voiced plosives in bilabial, alveolar and velar positions, as well as voiceless and voiced labiodental fricatives. It also includes /l/ and /w/. However, /r/ is not in Cantonese but in English. For syllable structure, Cantonese syllable structure is (C)V(V)(C); with realizations of CV, CVN and CVC (final C only consisting of unreleased plosives /p, t, k/), and the onset position is restricted to only allowing one consonant [1]. However, one special type of onsets resembles the English consonant cluster: in Cantonese, stop consonants with secondary articulation are present, which are also called "co-articulated stops" (e.g. /kwh/, /kw/, and /pw/) with a labialized gesture added to the plosive gesture. These gestures are highly overlapped in time (or, simultaneously, as in [1]) and treated as a single sound with two gestures. In all, clustering of consonants is not a legitimate syllable structure in Cantonese.

Previous Studies on Cantonese Acquisition of English Clusters Deletion and substitution of [r] cluster have been noticed in the literature for general phonological descriptions of Hong Kong English [4] [5] [6] Others studies emphasizes on the pedagogical importance of clusters as well as other common errors, which offered comprehensive solution for pronunciation problems [7] [8].

For studies specifically dealing with English clusters pronounced by Cantonese, Chan [9] is the only detailed study focusing on the distribution of realizations in initial clusters. She examined almost all English clusters produced by Cantonese learners. The result of her study showed that both deletion and substitution is observed among [r]-clusters. The deleted and substituted parts includes [r] in plosive-[r], fricative-[r]-clusters and threemember [r]-clusters ([spr-], [skr-], etc.). Secondly, deletion is reported to occur slightly more frequently than [w] substitution. Finally, all the plosive-[r]-clusters (pr-, tr-, kr-, br-, dr-, gr-) are reported to have both deletion and substitution. She offered a very detailed categorization of how many percentage of deletion/substitution exists for every C-r cluster.

Based on such phonological contrast, most studies suggests a negative transfer process from CV syllable structure in L1 Cantonese to L2 English consonant cluster structure. Constraint-based rules, such as Optimality Theory are often used to explain phonological processes of L2 English speech by Cantonese. For example, Yip [2] 's study concludes from loanword data that Cantonese-specific phonological constraints includes "OK-SYLLABLE", which means the syllable should be CVC, as permissible for Cantonese; and "MINIMAL WORD", which gives Cantonese the preference to the minimal length of each member of the syllable. Yam [3], however, explains the deletion of onset clusters in Cantonese pronunciation of English more concisely by the only constraint of "COMPLEX". To sum up, the phonological constraints related to onset clusters come from the consonant inventory and syllable structure of Cantonese.

However, findings of these studies may not be enough to describe the L2 phonological category formation details.

In natural speech data in our pilot study examining experienced learners, it is observed that the distinction of deletion and substitution for Cantonese speakers may not be so categorical. Sometimes a deleted [r]-cluster still have some traces of [r] acoustically. Also, it is observed that different place of articulation, which varies among labial, alveolar and velar clusters, may have different types of realizations. For example, clusters with an alveolar initial consonant are not observed with deletion (e.g., trip/tip).

Theoretical Models Explaining L2 Speech Acquisition After reviewing the previous studies, we noticed that different theoretic models of sound category formation may have different predictions of how Cantonese speakers may produce the L2 English clusters. In this section, two theoretic models, Perceptual Assimilation Model and Motor Theory, will be reviewed.

Best’s Perceptual Assimilation Model (PAM) suggested that two L2 sounds similar to a single L1 sound will be perceptually mapped onto the L1 category because of both of small perceptual distance, merging the L1 and L2 sounds into one sound in the phonological space [10]. In other words, an L1 to L2 assimilation will take place so that L2 is replaced by the closest L1 category [11] [12]. In Cantonese, both [r] and clusters are not in the L1 inventory, so they are likely to be mapped onto some L1 categories. Take /pr/ clusters as an example. In Cantonese, both /p/ and /pw/ are possible syllable onsets [4] Thus deletion (e.g., from /pr/ to /p/) or substitution (e.g., from /pr/ to /pw/) can be seen as two routes of category assimilation. If the quality of the [r] in cluster is categorically different between deletion and substitution, and deleted or substituted [r] no longer maintains phonetic traces of /r/, the Perceptual Assimilation Model will be supported.

Another possible explanation is the Motor Theory, which is based on the premise that speech acquisition was learned through articulatory gestures [13]. In articulatory phonetics, it is suggested that gestures are the atomic units of speech, and thus all speech events can be described by constriction location, constriction degree, and intergestural timing in complex gestural constellations [14]. Motor theorists believe that modifications on speech may result from gestural economy: it is often observed that a sound with complex gestures is reduced for ease of articulation [13] [14]. An example for the gestural analysis of complex sounds can be shown from the articulation of /l/ and /r. Both sounds have two gestures on the tongue, making these sounds complex to articulate. Both sounds had undergone gestural reduction in cases of L1 language development [15] [16] and L2 acquisition [17] [18] [19]. Even for L1, it has been demonstrated that there are articulatory differences in the production of the same sounds depending on their syllabic position [19] [20] [21]. It is possible that the L2 realizations of deletion or substitution were brought about by gestural reductions. If so, there might still be some traces of /r/ in their productions.

METHOD Based on the language phenomenon recorded by literature and theoretical models previously explained the phenomenon, this study aims to answer the following two research questions: Question 1: Are there any acoustic similarities or differences between Cantonese speakers’ production of English words beginning with C and C[r]? What are the factors influencing such acoustic differences? Do Cantonese speakers’ productions differ from those of native English speakers?

Question 2: Can the realizations be called deletion and substitution? If the L2 categories of clusters by Cantonese speakers are different from those by L1 English speakers, is the nature of acquisition categorical assimilation or gestural?

Participant and Stimuli The experiment included a production test for two groups of participants: native Cantonese and native English speakers. Both groups were recorded when they read the stimuli containing English initial [r]-clusters. The recordings were analyzed acoustically.

Three female Cantonese speakers participated in the study. They were all students from the School of Science and Engineering in a university in Hong Kong. They had a mean age of 23 years. They were all descendants of native Cantonese parents. They all attended high schools with English as the medium of instruction, and experienced an average of 20 years of studying English. They were not reported with any hearing or speech disorder, nor did they have any overseas experience longer than two weeks. Their average speech rate ranged from 121.6 to 143.6 wpm, within the normal range. Two male native English speakers from the USA were recorded with the same material. They had a mean age of 25 years and were exchange students at a university in Hong Kong.

Identical stimuli words containing initial clusters were used for both Cantonese and English speakers. Stimuli consisted of three types of words: target words and two types of control words. Target words were real words containing initial C-r clusters (e.g., break, treat, and great). All stimuli words were guaranteed a high wordfrequency by choosing them from a primary school word list [22]. Word frequency was considered to ensure that all participants read the stimuli fluently and easily.

Target words were selected according to four variables: (a) Voicing of the initial member of the cluster (e.g., prince and bring) (b) Three places of articulation of the initial member of the cluster, namely labial (/p/, /b/, /f/), alveolar (/t/, /d/) and velar (/k/, /g/) sounds (e.g., Bree, dream, and great) (c) Four vowel categories featuring high front, high back, low front and low back (e.g., Bree, grew, bread, and cry) (d) Three types of syllable structure, namely CrV, CrVN and CrVC (e.g., grow, green, and ground) Control words were chosen to contrast with the target words in two ways: For contrasting C-r cluster with non-[r] environment, words with single stop initial such as bit, tip, and keen are chosen; to see if cluster [r] was assimilated to other approximants, words with single liquid or glide initial such as rear, win, and lean were chosen.

All stimuli were then put into a coherent short passage (see appendix) to ensure that all participants read the stimuli fluently and naturally in conversational style, without any problem in spelling out the words. Some originally included stimuli tokens were deleted because the vowels are articulated significantly wrong. e.g., pronouncing grind as "[grInd]”.

Originally we designed a set of stimuli consisting of six tokens per place category with distinction on vowels.

But it was extremely hard to control the vowels and at the same time keep the word frequent high, so we did not control strictly about the vowel distribution. As a result the number of tokens was 55 for each speaker. 55*5= 275 tokens were analyzed in total.

Data Collection All participants did the recordings in the Research Laboratory for Phonetics and Cognitive Studies at City University of Hong Kong. They were recorded at the sampling frequency of 44100Hz in mono channel. Participants were instructed to read the passage three times and for each stimulus, the steadiest word in three repetitions was picked for analysis.

Speakers were asked to sit in front of the recording apparatus and read the stimuli with chair height adjusted to their ease of reading. Microphone was placed with a 10 cm, 45 degree distance away from the speaker’s mouth. The stimuli sheet, both pages in a paper stand, was placed in front of the speakers’ eye and subject to the speakers’ adjustment. The font size was 24. Speakers had the chance to try recording and familiarizing with the equipment.

The researcher left the room while recording was in progress.

Measurement The audio recording of each participant and control speaker was cut into 19 sentence-blocks for the purpose of labeling. Within the sentences, target and control words were labeled out by text-grid and each sentence using praat, and were normalized for duration by the average speech rate of the three speakers. The segmentation within the word was done to segment out the [r] transition. In general, [r] is regarded as the voiced transition between the initial consonant and the vowel. And in detail, we took after Peterson and Lehiste [23] and Naeser [24]’s way of

segmentation: the onset of [r] was indicated by the start of voicing, and the offset was set at the beginning of the steady state of vowel which is indicated by the steady state of formants.

Acoustic measurements were done to quantify the attribute of the target and control words. To the ease of labeling, we assigned the label C1 and C2 to the initial and final consonant, [r] to the [r] transition and V to the vowel. See Figure 1 for an example of segmentation for “print”: p C1

r [r]

i V

nt C2

Figure 1: segmentation labeling for “print” in the study Three acoustic parameters were measured: F2 value, F3 value and relative duration. F2 and F3, especially F3, are traditionally deemed to be distinctive for the [r] feature, therefore they are measured. The F2 and F3 for [r] are formant frequency value on average for the whole transition because it is found that generally no steady state is seen for [r] in C-r clusters so getting an average value is fairer. The F2 and F3 for the steady state vowel part were also measured to serve as a comparison so as to find the difference between [r] and vowels and whether there is a vowel effect on [r].

The duration for [r] transition was measured indirectly by using percentage for transition duration within the syllable. This is because the absolute durations for different words were distinct and relative duration can reveal the percentage of duration more accurately. Both the duration of the initial consonant and [r] transition were measured.

RESULTS Either deletion- or substitution-like pronunciations were used by all participants for Cantonese speakers.

However, only a part of the participants’ productions had perceivable deletion or substitution. We used acoustic analysis below to show the spectral differences of F2, F3 and duration of the experiment words and control words by showing the effect of speakers, consonants and vowels.

Spectral difference by speakers The first step of acoustic analysis involved comparing acoustic parameters between Cantonese and native English speakers. Results showed that pronounce [r] in clusters differently because both F2 and F3 are significantly different between the two groups of speakers [F2: t=3.41, df=124, p=.001; F3: t=9.94, df=124, p=.000]. However, no such significance was shown for duration. The difference of F3 was substantially larger than that of F2. Bar chart below showed that a categorical difference in F3 exists between Cantonese and English speakers, which might indicate that F3 was the primary acoustic cue for the non-native-like nature of Cantonese [r] in clusters. (See Figure 2 below)

Figure 2: Comparison of F2 and F3 by Cantonese and English speakers

Spectral difference by Consonant Given the knowledge that Cantonese speakers' cluster being different from English speakers', we investigated whether voicing, syllable and place of articulation may have an impact on F2, F3, and relative duration of [r].

Independent t-test results showed that voicing was only significant for relative duration: voiced consonants had significantly larger duration of [r] than voiceless consonants. For syllable structure, F3 of CVN type was significantly higher than the other two types. The influence of place of articulation could be illustrated by F3 value, because F3 of the alveolar clusters was significantly higher than that of other two places (see Figure 3). Statistics were shown as follows: For voicing, [F2: t=1.078, df=117, p=.283; F3: t=.951, df=117, p=.344; rd[r]: t=-3.834, df=117, p=.000]. For syllable, [F2: F(2, 101)= 3.985, p=0.022; F3: F(2, 101)=1.725, p=.183]. For place, [F2: F(2, 101)=3.895, p=.063; F3: F(2, 101)= 3.510, p=.055]. The influence of place of articulation had shown that alveolar clusters had higher F3 than other places of articulation for both Cantonese and English speakers. Interestingly, the high F3 value for Cantonese was not significant, unlike that of English speakers [F (2, 79)=-5.435, p=.0017].

Figure 3: Comparison of F3 across places of articulation by Cantonese speakers Another related attribute of the influence of place of articulation was the occurrence of affrication for alveolar clusters (see waveform in figure 4 showing "trip", the affrication was shown with high frequency quality). All 65 tokens of alveolar sounds had long affrication with a mean length of 35.5% of relative duration. The finding was consistent with the higher F3 which is typical for affricated sounds.

Figure 4: Alveolar cluster affrication in “trip� by a Cantonese subject

Spectral difference by Vowel For Cantonese speakers, vowel and [r] transition had significant difference in terms of both F2 and F3. [F2: t=10.58, df=125, p=.000; F3: t=14.92, df=125, p=.000], showing the vowel and [r] transition being significantly different in formant values (see Figure 5).

Influence of vowel categories onto F2, F3 and rd [r] was also examined. Among four vowel categories, the difference was significant only for F2 [F(3,115)=27.291, p=.000] but not for F3[F(3, 115)=2.160, p=.097] for Cantonese speakers. The scatter plot in figure 6 indicated that high F2 of front vowels was significantly different

from that of back vowels. No such a tendency was shown for F3. This may imply that quality of vowel will influence the quality of [r] in the cluster anticipatorily, leaving a similar F2 to the preceding [r]. We could infer that the frontness or backness of [r] was significantly influenced by that of the vowel because F2 is the acoustic feature for frontness or backness. This indicates that the vowel quality have an influence on the [r] quality.

Figure 5: Comparison of F2 and F3 by vowel categories: colors represent vowel types. The left column represents Cantonese speakers and the right represents English ones.

DISCUSSION Deletion or Reduction?

The results above showed that F2, F3 and rd [r] vary by different influencing factors. However, what is the nature of [r] in cluster? Does deletion and substitution really exist in acoustic measures?

The audible deletion of [r] was characterized by a short duration. A preliminary screening showed that words whose rd [r] was shorter than 5% of the entire word has the attributes of deletion audibly, while longer rd [r] indicated a quality that is closer to substitution. If the Perceptual Assimilation Model supports our finding, then C-r cluster production will have clear-cut category between deletion and substitution. Otherwise, if the gestural model is a better explanation, there will be a significant within-category difference in deletion or substitution.

Independent t-test was used to test between cluster words categorized as deletion (rd [r]≤5%) and control words with initial plosive (e.g., bit, tip, and keen). The result was significant for F3 but not for F2 for Cantonese [F2: t=-2.508, df=37, p=.122; F3: t=-2.647, df=37, p=.024], indicating that the quality of deleted clusters was different from the non-cluster control words, and further implying that deletion was not categorical (see Figure 6).

Figure 6: Comparison of F2 and F3 for ‘deleted’ cluster and non-cluster words. Here, deletion is defined as relative duration less than 5% of the word.

Comparison of Reduced [r] with Candidate Categories Comparison with other approximants The non-categorical nature of deletion and substitution suggests a questionable status of the quality of cluster [r]. To investigate this, the F2 and F3 quality of [r] was compared with [w] and [l] for goodness in assimilating as one exemplar. The result was shown in the bar chart below (see Figure 7). For Cantonese speakers, the cluster [r] (mean F2=1544, F3=2459) had a F2 and F3 value in between initial [r] (mean F2=1491, F3=2342), [w] (mean F2=1756, F3=2656), and [l] (mean F2=1517, F3= 2895). The cluster [r] was closer to initial [r] but still falling in between initial [r] and [w]. Statistically, the difference between the approximants and cluster [r] showed that only F3 was significantly different [F2: F(3, 136)=2.642, p=.056; F3: F(3, 136)=3.203, p=.009]. Tukey's test indicated that F3's significance was primarily caused by [l] and both [r] and [w] sounds did not show significant difference changes. This showed that [r] was not categorically assimilated to any of the three initial glide/liquid candidates, especially not substituted to [w]; instead, the cluster [r] was within the continuum between [r] and [w], supporting the gestural model.

Figure 7: Comparison of F2 and F3 between [r] in cluster and initial approximants Comparison with vowels Further investigation on quality of cluster [r] was done on comparison between cluster [r] and vowel gestures.

For Cantonese speakers, F2 value (indicating the frontness or backness) and F3 gesture (indicating tip gesture) of four vowel categories were examined to see which was closer to cluster [r]. Results showed that F2 of cluster [r] was similar to the quality of low back vowels [o]. But F3 was still deviant from the norm of all vowels [F2: F (4, 78)=5.245, p=.078; F3: F(4, 78)=8.674, p=.144]. (See Figure 8)

Figure 8: Comparison of F2 and F3 between [r] in cluster and vowels The results showed that the nature of the cluster [r] was closer to [r] but still had some similarity to [w] or [ɔ], without assimilating categorically to one single sound. This can be seen as an evidence for the existence of gestural reduction rather than categorical assimilation, diverging from the category assimilation hypothesis of PAM. The analysis on the nature of the reduced [r] indicated that Cantonese speakers would reduce [r] to an extent which, at least acoustically, not as a good category to replace any of the probable candidate categories of assimilation, regardless of whether the category was an approximant ([r], [l], [w]) or a vowel ([u], [ɔ]). This indicated that L1 influence was not fully sufficient to account for L2 realizations, and again brought about the issue that more finegrained, phonetic explanations are needed for accounting L2 phonology.

The Characteristics of Alveolar Clusters From the results on comparison by place of articulation, we could see, from both F3 value and the highfrequency pattern on the spectrogram, that affrication exclusively exists for alveolar clusters. Affrication may be a strategy for both Cantonese speakers to efficiently retain some quality of the cluster and at the same time simplify the gestures, thus creating the affrication quality. On the surface we may generalize that the category of [tr] cluster is assimilated to [tʃ]. In terms of gestural explanation, this is probably due to a) the jaw cycle pushed slightly backwards the place from alveolar to post-alveolar, causing the F3 quality of the transition [r] to be significantly higher than that of [r]; and b) [tr] involves both [t] and [r]. The gesture of [t] is an alveolar closure) both [r] involved a rising gesture of tongue tip which created a conflict in gestural coordination, resulting a compromising gesture of [tʃ]. The reduced tip gesture thus resulted in a high F3 [25] [26]. Therefore, gestural reduction could be seen as a reason for high F3 in alveolar clusters. This observation is also in line with the gestural model.

Another interesting finding is that native English speakers also applied the same realizations on alveolar clusters. In native English [tr] production, F3 was also significantly higher than its labial and velar counterparts.

This might indicate that the gestural shift on the lip or tongue tip (which indicates F3) had made significant changes in volume for native English speakers as well, resulting gestural reduction, which may also due to the foresaid conflict of gestural coordination. The fact that gestural reduction was cross-linguistically significant for alveolar clusters indicates that modification on C-r clusters was not purely phonological but due to phonetic universals in similar category locations for English and Cantonese in the phonological map.

Insights into L2 Speech Learning The Speech Learning Model (SLM) may give some insight into explaining the above finding in denying that L2 categories will only assimilate to specific L1 categories. SLM posits that very experienced L2 learners (in this case, Cantonese speakers with 20 years of English learning experience) may establish, after a long time of L2 exposure, an intermediate category when L2 category exemplar is a good one in L1 and is similar to L1. And it is more likely to happen where the acoustic or gestural cue from the L1 category is hard to detect [27]. Flege argueed that L1 and L2 will confluence as the two categories continue to exist and two languages continue to be used in daily communication. In Flege’s [27] study, he examined the stop consonant production of English-French bilinguals by different levels of experience in second language learning. Although French and English alveolar stop [t] differs in VOT, they are basically similar sounds for bilingual learners. The results of a production test show that more experienced learners have established a new category for both French and English [t], with its VOT in the middle of that of the L1 and L2 category as a compromise. This is just as the status of cluster [r] between [r] and [w] in this study. Here as well, a new, confluence category may be established if the learner is experienced. This also conforms to the hypothesis of SLM that L1 is also influenced by the intervention of L2, rather than a one-directional influence from L1 to L2. Future studies may require further examination of the Cantonese speakers’ native sounds to see if similar influence from L2 to L1 has taken place to see if the L1 initial consonant production is influenced by L2 English.

CONCLUSION The main findings of the studies in the report period were in twofold: firstly, we found that F3 is a key phonetic cue to gestural reduction for cluster [r]. Secondly, a clear-cut phonological category for labeling of "deletion" and "substitution" in Cantonese' production of English clusters might not be appropriate. Instead, we proposed that the

modification Cantonese speakers made when articulating English clusters was actually a gestural reduction process.

When the cluster [r] was produced, complex gestures on the tongue tip would trigger gestural reduction, which was indicated by a higher F3 value. However, a pure production study is not enough to give account of how L2 sounds are learned because how Cantonese and English speakers perceive those sounds are not investigated, and we are not certain whether the L2 category also have a perceptual reality.

ACKNOWLDGEMENT This research is supported by CTL-SSRG grant, City University of Hong Kong.

APPENDIX The stimuli passage is shown below. Target words are in red, and control words are in blue and brown.

Double dash indicates a segment of sentence.

Hello everyone, my name is Bree. My topic of the presentation today is my dream. //I have a great dream. I want every friend of mine can afford the fee of the train to many places. //I also want them to pray, just like a priest, so they don’t have to wash and dry their clothes every day. //And they can drink milk and eat bread without looking at the price or paying a tip.

Moreover, my friends can draw everything they want to try, and they can grow many many big apple trees in their gardens. //By the way I hope my brave friends won’t drop from the top to the ground and then died. //Instead, it’s much better to glide from the tree and after that they can lean on it and have some rest. //And at school, I wish they don’t have to do group presentations in front of the class president, because they can just flee away like a cat. //And when they play football after school, they won’t cry even if a truck has hit them. //Instead, they can bring the football home or go for a trip even if their legs broke.

Again, sometimes when you pray, you can get more money to pay for things you dream of. //Like now, my stomach is dead crazy for a bite of fried chicken burger with raw onion! //And get me some seaweed and crisps! By the way do you know the crazy story of the frog prince?// I’m so keen to it. I thought the princess is so proud of herself and I cry every time when I read it.

Well boys, soon will be Halloween and be bright! Remember to say “trick or treat” to get sweeties. //Even you face the risk of crushing with each other, it’s OK. //You can still find a way to win the game. Lead your team and rob for free sweeties! //After that your friends and parents will even pay the price of a cream soda for you after you are bumped blue and green. //Well, I think it’s time to lie down and sleep but I grind my teeth every night when I dress on my clean night gowns.

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