PERCEPTUAL STRATEGIES IN PRELINGUAL SPEECH SEGMENTATION

Previous work has suggested that infants may segment continuous speech by a BRACKETING STRATEGY that segregates portions of the speech strea m based on prosodic cues to their endpoints. The two present studies w ere designed to assess whether infants also can deploy a CLUSTERING ST RATEGY that exploits asymmetries in transitional probabilities between successive elements, aggregating elements with high transitional prob abilities and identifying points of low transitional probabilities as boundaries between units. These studies examined effects of the struct ure and redundancy of speech context on infants' discrimination of two target syllables using an operant head-turning procedure. After discr imination training on the target syllables in isolation, discriminatio n maintenance was tested when the target syllables were embedded in on e of three contexts. Invariant Order contexts were structured to promo te clustering, whereas the Redundant and Variable Order contexts were not. Thirty-six seven-month-olds were tested in Experiment I, in which stimuli were produced with varying intonation contours; 36 eight-mont h-olds were tested in Experiment 2, in which stimuli were produced wit h comparable flat pitch contours. In both experiments, performance of the three groups was equivalent in an initial 20-trial test. However, in a second 20-trial test, significant improvements in performance wer e shown by infants in the Invariant Order condition. No such gains wer e shown by infants in the other two conditions. These studies suggest that clustering may complement bracketing in infants' discovery of uni ts of language.