Peter W. Jusczyk

Speech perception in infants.

Discriminiationi of synthetic speech sounds was studied in 1- and 4-month-old infants. The speech sounds varied along an acoustic dimension previously shown to cue phonemic distinctions among the voiced and voiceless stop consonants in adults. Discriminability was measured by an increase in conditioned response rate to a second speech sound after habituation to the first speech sound. Recovery from habituation was greater for a given acoustic difference when the two stimuli were from different adult phonemic categories than when they were from the same category. The discontinuity in discrimination at the region of the adult phonemic boundary was taken as evidence for categorical perception.

A precursor of language acquisition in young infants

Abstract Four-day-old French and 2-month-old American infants distinguish utterances in their native languages from those of another language. In contrast, neither group gave evidence of distinguishing utterances from two foreign languages. A series of control experiments confirmed that the ability to distinguish utterances from two different languages appears to depend upon some familiarity with at least one of the two languages. Finally, two experiments with low-pass-filtered versions of the samples replicated the main findings of discrimination of the native language utterances. These latter results suggest that the basis for classifying utterances from the native language may be provided by prosodic cues.

Clauses Are Perceptual Units For Young Infants

Abstract Most theories of language acquisition implicitly assume that the language learner is able to arrive at a segmentation of speech into clausal units. The present studies employed a preference procedure to examine the sensitivity of 7-10-month-old infants to acoustic correlates of clausal units in English. From a recording of a mother speaking to her child, matched samples were constructed by inserting pauses either at clause boundaries or at within-clause locations. The infants oriented longer to the samples segmented at the clause boundary. A second experiment confirmed that these preferences depended on where the pauses were inserted in the samples. These findings have important implications for understanding how language is learnable. The prelinguistic infant apparently possesses the means to detect important units such as clauses, within which grammatical rules apply.

The head-turn preference procedure for testing auditory perception

Abstract The Head-Turn Preference Procedure (HPP) is valuable for testing perception of sustained auditory materials, particularly speech. This article presents a detailed description of the current version of HPP, new evidence of the objectivity of measurements within it, and an account of recent modifications.

Phonotactic cues for segmentation of fluent speech by infants

There is growing evidence that infants become sensitive to the probabilistic phonotactics of their ambient language sometime during the second half of their first year. The present study investigates whether 9-month-olds make use of phonotactic cues to segment words from fluent speech. Using the Headturn Preference Procedure, we found that infants listened to a CVC stimulus longer when the stimulus previously appeared in a sentential context with good phonotactic cues than when it appeared in one without such cues. The goodness of the phonotactic cues was estimated from the frequency with which the C.C clusters at the onset and offset of a CVC test stimulus (i.e. C.CVC.C) are found within and between words in child-directed speech, with high between-word probability associated with good cues to word boundaries. A similar segmentation result emerged when good phonotactic cues occurred only at the onset (i.e. C.CVC.C) or the offset (i.e. C.CVC.C) of the target words in the utterances. Together, the results suggest that 9-month-olds use probabilistic phonotactics to segment speech into words and that high-probability between-word clusters are interpreted as both word onsets and word offsets.

Infants' sensitivity to allophonic cues for word segmentation

A series of four experiments was conducted to determine whether English-learning infants can use allophonic cues to word boundaries to segment words from fluent speech. Infants were familiarized with a pair of two-syllable items, such asnitrates andnight rates and then were tested on their ability to detect these same words in fluent speech passages. The presence of allophonic cues to word bound-aries did not help 9-month-olds to distinguish one of the familiarized words from an acoustically similar foil. Infants familiarized withnitrates were just as likely to listen to a passage aboutnight rates as they were to listen to one aboutnitrates. Nevertheless, when the passages contained distributional cues that favored the extraction of the familiarized targets, 9-month-olds were able to segment these items from fluent speech. By the age of 10.5 months, infants were able to rely solely on allophonic cues to locate the familiarized target words in passages. We consider what implications these findings have for understanding how word segmentation skills develop.

Sensitivity to discontinuous dependencies in language learners: evidence for limitations in processing space

Five experiments using the Headturn Preference Procedure examined 15- and 18-month-old childrens sensitivity to morphosyntactic dependencies in English. In each experiment, the children were exposed to two types of passages. Passages in the experimental condition contained a well-formed English dependency between the auxiliary verb is and a main verb with the ending -ing. Passages in the control condition contained an ungrammatical combination of the modal auxiliary can and a main verb with the ending -ing. In the experiments, the distance between the dependent morphemes was systematically varied by inserting an adverbial of a specified length between the auxiliary and main verbs. The results indicated that 18-month-olds are sensitive to the basic relationship between is and -ing, but that 15-month-olds are not. The 18-month-olds, but not the 15-month-olds, listened significantly longer to the passages with the well-formed English dependency. In addition, the 18-month-olds showed this preference for the well-formed dependency only over a limited domain of 1-3 syllables. Over domains of 4-5 syllables, they showed no significant preference for the experimental over the control passages. These findings indicate that 18-month-olds can track relationships between functor morphemes. Additionally, these findings are consistent with the hypothesis that 18-month-olds are working with a limited processing window, and that they are only picking up relevant dependencies that fall within this window.

The prosodic bootstrapping of phrases: Evidence from prelinguistic infants

Abstract The current study explores infants’ use of prosodic cues coincident with phrases in processing fluent speech. After familiarization with two versions of the same word sequence, both 6- and 9-month-olds showed a preference for a passage containing the sequence as a noun phrase over a passage with the same sequence as a syntactic non-unit. However, this result was found only in one of the two groups, the group exposed to a stronger prosodic difference between the syntactic and non-syntactic sequences. Six month olds were tested in the same way on passages containing verb phrases. In this case, both groups preferred the passage with the verb phrase to the passage with the same word sequence as a syntactic non-unit. These results provide the first evidence that infants as young as 6 months old are sensitive to prosodic markers of syntactic units smaller than the clause, and, in addition, that they use this sensitivity to recognize phrasal units, both noun and verb phrases, in fluent speech. This ability to use phrase-level prosodic cues is variable, however, and appears to depend on the strength or number of cues associated with these syntactic units.

Infants' Perception of Phrase Structure in Music

A visual preference procedure was used to examine 6- and 41/2-monthold infants’ sensitivity to phrase structure in music. Sections of Mozart minuets were divided into segments that either did or did not correspond to the phrase structure of the music. Infants in both age groups listened significantly longer to the appropriately segmented versions. Their behavior accorded well with judgments of the same materials made by adults, suggesting that protracted musical experience may not be necessary to perceive phrase structure in music. Strong correlations were found between certain musical variables and the infants’ preferences for the musical passages, pointing to acoustic properties that may be important for defining musical phrases.

When prosody fails to cue syntactic structure: 9-month-olds' sensitivity to phonological versus syntactic phrases ☆

According to prosodic bootstrapping accounts of syntax acquisition, language learners use the correlation between syntactic boundaries and prosodic changes (e.g., pausing, vowel lengthening, large increases or decreases in fundamental frequency) to cue the presence and arrangement of syntactic constituents. However, recent linguistic accounts suggest that prosody does not directly reflect syntactic structure but rather is governed by independent prosodic units such as phonological phrases. To examine the implications of this view for the prosodic bootstrapping hypothesis, infants in Experiment 1 were presented with sentences in which pauses were inserted either between the subject noun phrase (NP) and verb or after the verb. Half of the infants heard sentences with lexical NP subjects, in which prosodic structure is consistent with syntactic structure. The other half heard sentences with pronoun subjects, in which prosodic structure does not mirror syntactic structure. In a preferential listening paradigm, infants in the lexical NP condition listened longer to materials containing pauses between the subject and verb, the main syntactic constituents. However, in the pronoun NP condition, infants showed no difference in listening times for the two pause locations. To determine if other sentence types containing pronoun subjects potentially provide information about the syntactic constituency of these elements, infants in Experiment 2 heard yes-no questions with pronoun subjects, in which the prosodic structure reflects the constituency of the subject. Infants listened longer when pauses were inserted between the subject and verb than after the verb. Taken together, our results suggest that the prosodic information in an individual sentence is not always sufficient to assign a syntactic structure. Rather, learners must engage in active inferential processes, using cross-sentence comparisons and other types of information to arrive at the correct syntactic representation.