A rhythmic bias in preverbal speech segmentation

Four studies using a variant of the conditioned head turning procedure, in which response latencies to extraneous noises occurring at different junctures within synthetic syllable strings served as the dependent variable, investigated 6- and 9-month-old infants representations of familiar and novel syllable pairs manifesting diverse rhythmic patterns. Familiar bisyllables tended to be perceived similarly a by both agr groups: These bisyllables were perceived as being cohesive, without regard to whether they manifested trochaic (longer-shorter) or iambic (shorter-longer) rhythm. Novel bisyllables were perceived differently by the two age groups. Six-month old appeared to perceive segmentally novel, but rhythmically familiar, bisyllables as cohesive, whereas they failed to perceive rhythmically novel, but segmentally familiar bisyllables in the same fashion. Similar patterns of results were obtained with trochaic and Iambic bisyllables. Nine-month-olds, however, were differentially sensitive to different rhythmic patterns. Older infants appeared to perceive novel bisyllables as cohesive only when they manifested trochaic rhythm, whether the bisyllables were segmentally or rhythmically never. Nine-month-olds behavior is consistent with the possibility thar they have adopted a metrical strategy for segmentation, as A. Cutler (1990 and elsewhere) has argued is the case for novice and expert English speakers alike. The plausibility of such a strategy with respect to the nature of child-directed speech is discussed, as are possible consequences for acquisition of such a strategy. (C) 1996 Academic Press, Inc.