Volume 4, Issue 1 - Rhythm, Speech Timing, and Perceptual Processing

The division of languages into stress-, syllable-, and mora-timing is said to be supported by experiments showing that languages are discriminated only if they belong to different rhythm classes, a distinction said to be reflected in the duration and variability of consonantal and vocalic intervals (timing). The role of rhythm classes in discrimination is tested here along with the alternative that discrimination is due to speaking rate and F 0 differences and is independent of rhythm class. Five AAX experiments with English as context (AA) and Polish, Danish, Spanish, Greek, or Korean as test (X) were conducted using the sasasa transform and modifying F 0 and speaking rate, so as to compare responses to stimuli that retained the original speaking rate and F 0 of each language and stimuli that were stripped of this information (speaking rate, F 0 , or both) while retaining their timing. Discrimination was possible both across and within rhythm classes when speaking rates differed between context and test but was largely impossible once speaking rate differences were eliminated. F 0 also played a significant if less consistent role in discrimination. The changes in responses associated with speaking rate and F 0 indicate that language discrimination arises from interactions between prosodic factors and that timing contributes but little. Consequently the results cast doubt both on the ecological validity of the sasasa transform, which brings timing to the fore while eliminating F 0 modulation, and on the rhythm class typology said to be reflected in timing distinctions.

The study examines rhythmic convergence between speakers of American and Indian English. Previous research has shown that American English shows tendencies towards stress-timing, and Indian English has been claimed to be syllable-timed (Crystal 1994). Starting from the view that languages differ in their rhythmic tendencies, rather than that they have categorically different rhythmic properties, we examine in an acoustic study the rhythmic tendencies of the two languages, and whether these tendencies can change in the course of an interaction. The focus is on temporal properties (specifically, the duration of stressed syllables and of feet). The results show evidence of mixed rhythmic properties for both languages, with Indian English being more syllable-timed than American English. American speakers show a trend towards changes in foot duration that can be interpreted as accommodation in speech rate or as convergence towards a more syllable-timed foot duration pattern. One Indian English speaker converges in both examined properties towards a more stress-timing pattern. The results are discussed within a dynamical model of rhythmic structure (Saltzman, Nam, Krivokapić, and Goldstein 2008). It is suggested that rhythmic convergence can arise via a tuning between speakers of the prosodic interoscillator coupling function that is proposed in that model.

The present paper examines glottal stops and the glottalisation of word-initial vowels in Polish and German. The presence of glottal marking is studied depending on speech style (‘speech’ vs. ‘dialogue’), prominence, phrasal position, speech rate, word type, preceding segment, and following vowel height. A question is also posed about the extent to which glottal marking might be dependent on the rhythmic structure of a given language or style. We analyzed recordings of 18 Polish and German speakers. The results point to significant differences between the two languages. In German, glottal marking occurs significantly more often (63.4%) than in Polish (45%). Whereas in both languages (and both styles) the majority of prominent vowels are more often glottally marked than non-prominent vowels, in German word-initial non-prominent syllables are also marked relatively often. Regarding phrase position, glottal marking occurs significantly more often at the phrase-initial position compared to phrase-medial position in Polish, while no such difference has been found in German. In addition, it is shown that in both languages glottal marking is strongly dependent on the tongue height of the marked vowel: low vowels are more frequently glottalised than non-low vowels. Finally, glottal marking in Polish is more likely to occur when rhythmic variability shifts towards the ‘indeterminate’, strengthening the hypothesis that glottal marking facilitates perceptual grouping.

This study employs a stress priming paradigm to investigate sensitivity to metrical structure in speech planning and production in Australian English. Target words with iambic stress were preceded by primes with either congruent or incongruent stress and also embedded in metrical contexts biased towards either persistent foot types (Experiment 1) or variable foot types (Experiment 2). Both naming latency, the time from stimulus presentation to the onset of speech, and phonetic patterns showed sensitivity to metrical manipulations. The paradigm produced stress errors, iambic targets produced as trochees, and variation in vowel formants and syllable duration as a function of metrical context. Patterns in the reaction time data indicated sensitivity to global metrical biases calculated over feet. When the metrical bias was toward persistent feet, iambs were produced more quickly in the congruent stress context. When the metrical bias was reversed, iambs were produced more quickly in the incongruent stress context. This pattern of results supports a speech production model that represents metrical structure and allows competition at the metrical level to influence phonetic variability.

Phonological models of intonation use abstract categories, such as pitch accents, to build a bridge between continuous modulations in F 0 contours (on the substantial side) and post-lexical meaning (on the functional side). However, recent research on Romance, Germanic, and non-Indo-European languages shows that sentence modality contrasts (i.e., question vs. statement) are often realized not only with different F 0 contours, but also through differences in individual phone duration or global speech rate. If these durational differences were also used as a cue in the perception of sentence modality contrasts, phonological categories in current models of intonation would qualify as excessively underspecified, and they should be expanded in order to include phonetic information on the temporal dimension as well. In this paper we evaluate the role of durational differences as a cue to the perception of sentence modality contrasts in the Neapolitan regional variety of Italian. Read sentences were resynthesized by switching durational and intonational patterns of questions and statements, and used in a forced-choice identification task. The results show that listeners exclusively rely on F 0 , thus suggesting that, at least for this specific contrast in this specific variety, phonological representations of intonational contrasts do not need to be enriched with phonetic detail at the durational level.

Even though the outcome of the perception of phonological patterns is categorical, this process might still arise from continuous dynamics. Here, we propose a unified dynamical account of three types of behavior that are usually studied in isolation: short-term perceptual competition, long-term perceptual habituation, and even longer-term perceptual learning. We develop a model and test its predictions in two speech identification tasks on an acoustic continuum between the French words [sɛp] and [stɛp]. When presenting stimuli sequentially from one end of the continuum to the other, we found that the presentation order systematically changed the position of the perceptual switch from one word to the other. We also found that response times were slower and more variable around this perceptual switch, regardless of its position on the acoustic continuum. And, throughout the experiment, participants became more sensitive to small acoustic differences between stimuli. Our model can account for these results and for a surprising finding, namely that the initial presentation order affected responses even late in the experiment. Overall, our results point to the importance of the relation between fast processes responsible for competition, and slow processes responsible for habituation and learning in explaining how listeners can perceive speech categorically in a way that is both flexible and robust.