The effect of sequence position

One of the main factors that influence articulatory timing between gestures in stop sequences is the position of the sequence being either SI, SF, word-medial, and across word boundaries. Several studies have demonstrated that gestural coordination in SI differs from SF stop sequences where SI sequences exhibit less gestural overlap and higher rates of acoustic releases of C1 in comparison with SF sequences (Chitoran 2002: Wright 1996). In his acoustic study of SI and word medial stop sequences in Tsou, Wright (1996:76) states that C1 release in SI sequences were 100% whereas they averaged 54% in word-medial stop sequences.

These variations in the articulatory timing and gestural coordination of different sequence positions have been explained in terms of perceptual recoverability. In SF position, listeners have access to transitional cues into C1 from the preceding vowel. However, due to the absence of transitional cues into C1 of the SI sequence, gestural overlapping of consonants in this position can threaten their perceptual recoverability. Wright explains that due to perceptual recoverability, stops in positions where transitional cues do not exist are produced with an audible release. Chitoran et al (2002) also add that because of the limitation of acoustic data in C1, the degree of overlapping in SI sequences is restricted to preserve as much acoustic data as possible.

Furthermore, Byrd (2003:11) also points out that SI and SF consonant sequences differ in terms of the coordination relationships between gestures. Timing relationships between gestures in SI position are stable in terms of gestural coordination whereas in SF position, these timing relationships are variable and do not exhibit stability. This view is also held by Gafos (2002). In his investigation of SI and SF consonant sequences in Moroccan Arabic, Gafos found that excrescent vowels resulting from the

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lag between C1 release and C2 onset in a consonant sequence were found to occur in SF consonant sequences and not in SI sequences where close transition between the gestures occurred. It is worth pointing out that the results of this study differ from the study of Tsou (Wright 1996) and of Georgian (Chitoran 2002) mentioned earlier where results from these studies showed that more C1 releases in the SI consonant sequences of both languages occurred due to perceptual recoverability issues.

The above described variations in gestural coordination patterns are also highlighted by the C-centre hypothesis (Browman & Goldstein 1988: Byrd 1994) which states that SI and SF consonant sequences are organized differently. The c-centre is considered to be the mid-point or centre of the gesture or gestures that make up a cluster (Byrd 1995:286). In SI consonant sequences, Browman & Goldstein (1988) claim that gestures are timed globally and organized with the following vowel by phasing their c- centre to the following vowel. This results in a steady relationship between the c-centre of the SI sequence and the following vowel whether the onset is a singleton or a cluster. On the other hand, in SF consonant sequences, a steady timing relationship was not found which suggests that the gestures are timed locally with the preceding vowel (Browman & Goldstein 2000). In these clusters, the left-most edge of the cluster is in a stable relationship with the preceding vowel regardless of the number of consonants in the cluster. The differences between gestural coordination patterns in SI and SF consonant clusters as put forward by the C-centre hypothesis can be further highlighted below:

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Figure 2.9 C-centre hypothesis for gestural coordination in SI and SF clusters: adopted from Marin & Pouplier (2002:381)

Contrary to SI and SF consonant sequences, the literature shows that articulatory timing relations and gestural coordination patterns across word boundary consonant sequences have not been thoroughly investigated. A fundamental question here is how gestures are coordinated across word boundaries and whether there is closer or looser gestural coordination in comparison to SI and SF stop sequences. In their study comparing gestural coordination patterns across word boundaries C#C in Taiwanese Chinese and American English, Gao et. al (2011:725) reported that there was closer gestural coordination across the word boundary in Taiwanese /tap#kap/ and /tap#tap/ sequences than in American English top cop /tɑp#kɑp/ and cop top /kɑp#tɑp/ sequences. The results of their acoustic study indicated that there was shorter lag between SF C1 offset and SI C2 onset in Taiwanese than in American English therefore closer gestural coordination in the former. They also point out that cross-linguistic gestural coordination differences show that different languages exhibit different coordination patterns.

Further studies have also shown that gestural coordination patterns across the word boundary can vary. In her study of English and Russian, Zsiga (2000) observed

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that in C#C stop sequences; there were more C1 releases in Russian than in English, suggesting that Russian exhibits less gestural overlap than English. Zsiga (2000:70) uses two measures of gestural overlap; % of release, the percentage of unmasked releases of C1 in the sequence, and duration ratio where she compared the duration of the cluster to the durations of the two consonants in intervocalic position. She compared gestural coordination across the word boundary in examples such as /k#t/ make tarts (Eng.) vs. pok tort (Rus.), and /p#t/ stop tarts (Eng.) vs. grop tam (Rus.) rowed there. Results indicate that the percentage of unmasked releases was 47% in Russian C#C sequences compared to 18% in English. In addition, Russian sequences exhibited a longer duration ratio than their English counterparts.

Other studies have also found similar results where gestural coordination was weaker between gestures across word and morpheme boundaries. According to Cho (1998), gestural coordination across word boundaries is weaker than within syllable boundaries: ‗the timing between two gestures within a single lexical entry is specified in the lexicon and it is preserved on the surface. On the other hand, the timing between two gestures created by morpheme-concatenation is not lexically specified, and is therefore potentially subject to any phonological change which can be produced by varying gestural overlap‘ (Cho 1998:15).

Cho (2001) argues that lag intervals between gestures within a word or morpheme seem to be shorter than across word or morpheme boundary and that these shorter intervals that are associated with a single lexical entry indicate that the gestures are more strongly bonded. As a result, the stronger bonding for gestures within a lexical entry would result in greater stability in intergestural timing as opposed to the weak bonding of gestures across different lexical items (Figure 2.10).

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Figure 2.10 Variability in articulatory timing between gestures within a single lexical entry and across morpheme or word boundary (#): from Cho (1998)

It is also worth pointing out that these studies only focus on gestural coordination patterns across word boundaries in C#C sequences. To the best of my knowledge, there are no studies investigating the effect of an increase in the number of stop consonants across the word boundary as in CC#C, C#CC, and CC#CC sequences on gestural coordination across the word boundary which is the main focus of this study.