the APriL project

APriL I: L1 acquisition of rhythm in Catalan, Spanish and English

The project had two objectives:

• to investigate the contribution of a number of phonological factors to cross-linguistic differences in speech rhythm in adults, testing one of the leading views on the basis for rhythm class distinctions between languages, which holds that the rhythm percept primarily reflects the phonological properties of syllable structure and vowel reduction.
• to clarify differences in L1 acquisition of rhythm in what are traditionally referred to as stress-timed and syllable-timed languages.

A production study addressed the first objective, examining the effects of syllable structure and vowel reduction on the rhythmic differences in adult speech for three languages that are reported to belong to different rhythmic classes (English: ‘stress-timed’, Spanish: ‘syllable-timed’, Catalan: ‘intermediate’). The results showed that, independent of syllable structure and vowel reduction, the rhythm class distinctions under consideration finely correlate with differences in the way the languages instantiate two prosodic timing processes, namely durational marking of prosodic heads, and prosodic boundary lengthening. We propose a prosody-based hypothesis regarding the importance of these durational patterns across languages for the perception of rhythmic contrasts.

A second production experiment sought to evaluate different rhythmic measures when applied to child speech and child-mother interactions. More specifically, interval-based rhythm metrics were applied to the speech of English, Catalan and Spanish 2, 4 and 6 year-olds, and to directly comparable speech data produced by their mothers. The results showed that for all three languages, child speech (CS) is more ‘vocalic’ (higher %V) than ADS and has greater variability in the duration of its consonantal intervals, especially in younger children. When normalised for speech rate, vocalic interval variability, however, tends to be lower in CS when normalised for speech rate, especially in English. Language differences are evident for ADS, CDS and child speech at all ages, with English showing a lower %V and higher variability scores. The findings also show that normalised variability indices most reliably reflect differences between child, child-directed and adult-directed speech cross-linguistically. In the paper submitted to Language and Speech (see Output) we evaluate the validity and adequacy of applying these metrics to developing speech, given the phonological differences, and also the difficulties more generally in interpreting metric scores, which may result from different and conflicting phonological and phonetic properties.

The findings from this experiment also show that child-directed speech is rhythmically more distinct from adult-directed speech in English than in Catalan and Spanish, as hypothesised, and that the rhythmic patterns in the mothers’ speech shows accommodation towards the patterns produced by the children. The latter finding contradicts the hypothesis that the properties of the adult language are exaggerated in child-directed speech. Finally, the findings have confirmed the hypothesis that children show cross-linguistic differences in rhythmic development depending on the rhythm class of the native language, with earlier acquisition reflected in adult-like patterns for Spanish children, and later acquisition for English children, which is attributable to differences in phonological and prosodic complexity between the languages.

In a third production experiment, the acoustic correlates of stress in early child speech were compared in English, Catalan, and Spanish, analyzing duration, pitch, intensity, and vowel quality. The results show that while children at age two still have difficulties in achieving segmental targets, they have already acquired near adult-like control over some of the acoustic parameters of stress. In all three languages, stressed syllables are consistently louder and have a higher pitch than unstressed syllables, but only Spanish two-year-olds use duration consistently.

This project was funded by the Generalitat de Catalunya (Ref. 2007 PBR 29; August 2007 – July 2008)