Segmentation of Rhythmic Units in Word Speech by Japanese Infants and Toddlers

Abstract

When infants and toddlers are confronted with sequences of sounds, they are required to segment the sounds into meaningful units to achieve sufficient understanding. Rhythm has been regarded as a crucial cue for segmentation of speech sounds. Although previous intermodal methods indicated that infants and toddlers could detect differences in speech sounds based on stress-timed and syllable-timed units, these methods could not clearly indicate how infants and toddlers perform sound segmentation. Thus, the present study examined whether Japanese infants and toddlers could segment word speech sounds comprising basic morae (i.e., rhythm units similar to syllables), on the basis of concurrent basic mora units within syllable units, using the new intermodal matching procedure. The results indicated that, regardless of their ages and linguistic abilities, Japanese infants and toddlers aged 6–25 months tended to segment Japanese words comprising basic morae sounds on the basis of concurrent basic mora units within syllable units. This implies that infants' and toddlers' use of syllable units for segmentation of speech sounds at an early age could be evident among many infants and toddlers learning various languages. Although this finding should be interpreted carefully, the present study demonstrated the utility of the new intermodal matching procedure for examining segmentation of speech sounds and word sounds by infants and toddlers, on the basis of specific rhythm units.

Constraints on infants’ ability to extract non-adjacent dependencies from vowels and consonants

“…Independent of this methodological consideration, earlier work has advocated for the syllable as a natural unit of speech perception already in early infancy: both newborns ( Bijeljac-Babic et al, 1993 ) and 2- to 4-month-olds ( Bertoncini and Mehler, 1981 , Eimas, 1999 ) were found to dissociate acoustically manipulated sequences based on syllabic rather than segmental or sound feature representations. Moreover, word segmentation studies suggest that 6- to 8-month-olds are able to group syllables into word-like units using distributional information (e.g., Aslin et al, 1998 ; Saffran et al, 1996 ) or prosodic cues (e.g., Cheong and Uehara, 2021 ; Nishibayashi et al, 2015 ) and recent modeling work corroborates the importance of syllables in prelinguistic perception and representation from the very beginning ( Räsänen et al, 2018 ). Since infants at around 8–10 months of age also start to produce canonical syllables in their babbling (e.g., Werker and Tees, 1999 ), it is evident that infants represent syllables as important units of computation at that age.…”