The Function of Duration and Stress- vs. Syllable-Timing
Irene Vogel ([email protected]) & Angeliki Athanasopoulou ([email protected])
University of Delaware
While the literal interpretation of syllable- vs. stress-timed isochrony has been amply disconfirmed1, the
impression of such a rhythmic distinction persists, and alternative means of capturing it phonologically 2
and phonetically1,3 have been proposed. All conclude that there are relatively clear cases of two basic
rhythmic types, with most languages falling somewhere between; however, there is less agreement as to
where different languages fall. Although the phonetic analyses consider different acoustic patterns, they
all combine data from various conditions, some of which are known to affect duration (i.e., stress, focus).
In the present paper, instead of simply combining measurements from stress and focus conditions along
with other measurements, we directly investigate the effects of these conditions on duration, and propose
that this approach yields additional insight into the rhythmic categories, and also provides a means of
including languages that would otherwise pose problems for classification (i.e., those with contrastive
vowel length and those without stress).
Despite other differences among languages depending on what calculations are used, it is consistently
observed that there is relatively little variability in vowel duration in the “classic” syllable-timed language,
Spanish, compared to languages such as Dutch and English1. While the difference is often correlated with
the presence / absence of reduced vowels, we propose that there is a more basic property involved that
accounts for this observation, as well as the variability of vowel duration more generally. Specifically,
syllable-timed languages are resistant to the manipulation of duration due to linguistic (prominence)
phenomena (i.e., stress and focus), while stress-timed (or at least non-syllable-timed) languages, by
contrast, do exhibit duration effects due to prominence. We thus investigate the grouping of languages into
syllable- or stress-timed categories based directly on the effects of stress and focus on duration.
Specifically, we calculate a Stress Ratio (SR) (stressed V/unstressed V), and a Focus Ratio (FR) (focused
V/non-focused V); if duration is not affected by a prominence property, the corresponding ratio will be
(close to) one.
(1) Stress Ratio: In syllable-timed languages, stress does not affect vowel duration; SR is close to 1.
(2) Focus Ratio: In syllable-timed languages, focus does not affect vowel duration; FR is close to 1.
A potential problem for previous analyses is that the rhythmic properties of languages with systematically
variable vowel durations (i.e., contrastive vowel length) cannot be meaningfully assessed by measures that
combine all vowels. We extend (1) and (2) to such languages, however, by examining short and long vowels
separately, thus permitting us to determine if their durations are basically stable, as in Spanish, or not.
Furthermore, while non-stress languages could in some trivial way all be considered syllable-timed,
assessing rhythm in terms of the effect of focus, or sentential prominence, on duration (i.e., Focus Ratio),
provides a means of comparing them, at least partially, to languages that do have stress.
We examined the duration effects of stress and focus in 11 languages (10 speakers per language). The
targets were 30 stressed and 30 unstressed vowels in real three-syllable words (x2 in languages with
contrastive vowel length). In non-stress languages, we compared Syllable1 (Syll1) vs. Syllable2 (Syll2),
avoiding potential confounds due to word-final prosody on Syllable3. All items were elicited in short
dialogues that placed them in focus and non-focus contexts.
Duration, and other prominence properties (i.e., mean F0, F0 change (from beginning to end of vowel),
Intensity and Centralization), were measured with Praat, and normalized using Z-scores. Binary Logistic
Regression Analyses (BLRAs) were conducted to provide not only information about significant
differences in the acoustic properties in the stress and focus conditions, but also the relative contributions
of the significant cues, especially duration, to the vowel distinctions. In syllable-timed languages, Duration
would not be the main classifier (cue) of Stress or Focus. We also calculated the SRs and FRs.
The BLRAs revealed Duration to be the main classifier of Stress in French, Portuguese and Finnish long
vowels (V:). Duration was also the main classifier of Syll1 vs. Syll2 in Indonesian and Vietnamese, but this
cannot be interpreted as a stress property in these languages. Duration was also significant, but only as a
secondary classifier of Stress, in Greek, Arabic long vowels (V:), and Finnish short Vowels (V). In
addition, Duration was a main classifier of Focus in Greek, Spanish, Portuguese, Arabic V, V:, Finnish V,
V:, Indonesian, Korean, and Vietnamese; it was a secondary classifier in French and Hungarian V:.
In Figure 1 shows the SR on the x-axis (based on non-focus context to avoid confound with focus properties)
and FR on the y-axis (based on stressed V, expected to be most subject to focus enhancement).
Figure 1: Language Distribution based on Stress Ratio and Focus Ratio.
As can be seen, Spanish, the classic syllable-timed language, has an SR of approximately 1, as do the others
close to the vertical line – showing a lack of lengthening for stress. French, Greek and Portuguese are the
least syllable-timed on this criterion. By contrast, Spanish has a higher FR, with more lengthening for focus
than French, though Portuguese is again the least syllable-timed. Of the languages with contrastive vowel
length, Hungarian is the only one that does not alter duration for either stress or focus. Arabic and Finnish
show a small increase for stress only in V:, since lengthening V would risk its merging with V:. Finnish
also shows a more substantial increase for focus, like Greek. The non-stress languages qualify as syllabletimed given their relatively low FR; SR only reflects syllable position here.
Thus, our findings align with previous studies in demonstrating the need for a more gradient view of timing,
and they corroborate several aspects of previous rhythmic groupings1,3, especially the general vowel
variability criterion1. Furthermore, by including BLRA results along with SR and FR, we are able assess
timing properties of languages with contrastive vowel length and non-stress languages, and thus arrive at a
more inclusive cross-linguistic view of rhythm. The BLRAs and ratio measures also offer a more nuanced
view not only of statistical findings, but also of the nature of the variability criterion, showing how different
phenomena may contribute differentially to variability in timing patterns.
1
Grabe, E., & Low, E.L. (2002). Durational variability in speech and the rhythm class hypothesis. In C.
Gussenhoven, and N. Warner (eds.), Papers in Lab Phon 7, pp. 515-546. Cambridge: CUP.
2
Dauer, R. (1987) Phonetic and phonological components of language rhythm. Proceedings of the XIth
International Congress of Phonetic Sciences, Talinn, Estonia, pp. 447-450.
3
Ramus, F., Nespor, M., & Mehler, J. (1999). Correlates of linguistic rhythm in the speech signal.
Cognition, 73, pp. 265-292.