James L. Morgan

Mommy and me: familiar names help launch babies into speech-stream segmentation.

How do infants find the words in the tangle of speech that confronts them? The present study shows that by as early as 6 months of age, infants can already exploit highly familiar words—including, but not limited to, their own names—to segment and recognize adjoining, previously unfamiliar words from fluent speech. The head-turn preference procedure was used to familiarize babies with short passages in which a novel word was preceded by a familiar or a novel name. At test, babies recognized the word that followed the familiar name, but not the word that followed the novel name. This is the youngest age at which infants have been shown capable of segmenting fluent speech. Young infants have a powerful aid available to them for cracking the speech code. Their emerging familiarity with particular words, such as their own and other peoples names, can provide initial anchors in the speech stream.

Newborn infants’ sensitivity to perceptual cues to lexical and grammatical words

In our study newborn infants were presented with lists of lexical and grammatical words prepared from natural maternal speech. The results show that newborns are able to categorically discriminate these sets of words based on a constellation of perceptual cues that distinguish them. This general ability to detect and categorically discriminate sets of words on the basis of multiple acoustic and phonological cues may provide a perceptual base that can help older infants bootstrap into the acquisition of grammatical categories and syntactic structure.

Structural Packaging in the Input to Language Learning: Contributions of Prosodic and Morphological Marking of Phrases to the Acquisition of Language.

Abstract The linguistic input to language learning is usually thought to consist of simple strings of words. We argue that input must also include information about how words group into syntactic phrases. Natural languages regularly incorporate correlated cues to phrase structure, such as prosody, function words, and concord morphology. The claim that such cues are necessary for successful acquisition of syntax was tested in a series of miniature language learning experiments with adult subjects. In each experiment, when input included some cue marking the phrase structure of sentences, subjects were entirely successful in learning syntax; in contrast, when input lacked such a cue (but was otherwise identical), subjects failed to learn significant portions of syntax. Cues to phrase structure appear to facilitate learning by indicating to the learner those domains within which distributional analyses may be most efficiently pursued, thereby reducing the amount and complexity of required input data. More complex target systems place greater premiums on efficient analysis; hence, such cues may be even more crucial for acquisition of natural language syntax. We suggest that the finding that phrase structure cues are a necessary aspect of language input reflects the limited capacities of human language learners; languages may incorporate structural cues in part to circumvent such limitations and ensure successful acquisition.

Limits on negative information in language input

Hirsh-Pasek, Treiman & Schneiderman (1984) and Demetras, Post & Snow (1986) have recently suggested that certain types of parental repetitions and clarification questions may provide children with subtle cues to their grammatical errors. We further investigated this possibility by examining parental responses to inflectional over-regularizations and wh-question auxiliary-verb omission errors in the sets of transcripts from Adam, Eve and Sarah (Brown 1973). These errors were chosen because they are exemplars of overgeneralization, the type of mistake for which negative information is, in theory, most critically needed. Expansions and Clarification Questions occurred more often following ill-formed utterances in Adams and Eves input, but not in Sarahs. However, these corrective responses formed only a small proportion of all adult responses following Adams and Eves grammatical errors. Moreover, corrective responses appear to drop out of childrens input while they continue to make overgeneralization errors. Whereas negative feedback may occasionally be available, in the light of these findings the contention that language input generally incorporates negative information appears to be unfounded.

Discovering words in the continuous speech stream: the role of prosody

Abstract Finding words in sentences is made difficult by the absence of obvious acoustic markers at word boundaries, such as silent pauses. Recent experimental evidence suggests that both adults and infants are able to use prosodic boundary cues on-line to constrain lexical access. French adults performing a word detection task were slowed down by local lexical ambiguities within phonological phrases but not across a phonological phrase boundary (Christophe, Peperkamp, Pallier, Block, & Mehler, J. Mem. Language (in revision)). Thirteen-month-old American infants who were trained to turn their heads upon hearing a bisyllabic word, such as ‘paper’, in a variant of the conditioned head-turning paradigm, responded more often to sentences that contained the target word than to sentences containing both its syllables separated by a phonological phrase boundary (Gout, Christophe, & Morgan, J. Mem. Language (in revision)). Taken together, these results suggest that both French adults and 13-month-old American infants perceive phonological phrase boundaries as natural word boundaries, and that they do not attempt lexical access on pairs of syllables which span such a boundary. We discuss the potential generalization of these results to other languages, the universality of prosodic boundary cues as well as their use in on-line syntactic analysis and syntax acquisition.

A role for the developing lexicon in phonetic category acquisition.

Infants segment words from fluent speech during the same period when they are learning phonetic categories, yet accounts of phonetic category acquisition typically ignore information about the words in which sounds appear. We use a Bayesian model to illustrate how feedback from segmented words might constrain phonetic category learning by providing information about which sounds occur together in words. Simulations demonstrate that word-level information can successfully disambiguate overlapping English vowel categories. Learning patterns in the model are shown to parallel human behavior from artificial language learning tasks. These findings point to a central role for the developing lexicon in phonetic category acquisition and provide a framework for incorporating top-down constraints into models of category learning.

Negative Evidence on Negative Evidence.

Previous work has shown that recasts may be contingent responses to childrens early ungrammatically. On this basis, it has been claimed that recasts provide negative evidence, thereby offsetting the need for linguistic constraints in theories of acquisition. This study explores whether children exploit negative evidence putatively provided by recasts by examining whether parental recasts are associated with childrens recovery from particular overgeneralization errors. Data from longitudinal investigations of 2 common syntactic errors reveal that recasts are related to childrens subsequent grammaticality. However, contrary to what would be expected if recasts serve as corrections, the data show that recasts are negative leading indicators of grammaticality. Finally, correction and negative evidence axe examined and are shown to be nonequivalent. Therefore, corrections in whatever form they might exist can offset only a limited subset of proposed innate constraints on language acquisition.

Facilitating the acquisition of syntax with cross-sentential cues to phrase structure☆

Abstract Several previous studies using miniature language methodology have shown that the acquisition of syntax is facilitated by language input that incorporates cues to sentence phrase structure. These studies have examined effects of LOCAL cues, such as prosody or function words, which are physically identifiable aspects of input and which directly indicate the phrase bracketing of individual input strings. In the present study, we examine the effects of CROSS-SENTENTIAL cues to phrase structure—cues that lack overt manifestations in individual strings, arise solely as consequences of the rule system underlying the input language, and must be extracted from input through comparisons of semantically and syntactically related strings. Grammars incorporating rules of pronominalization and permutation were used to generate input with cross-sentential cues. Subjects exposed to such input were completely successful in learning syntax, whereas subjects exposed to input generated by a simpler grammar (and lacking either local or cross-sentential cues) failed to learn complex aspects of syntax. Natural languages regularly include the types of rules that give rise to cross-sentential cues and also regularly possess multiple local cues to phrase structure. These patterns of universality, coupled with the consistent facilitative effects of structural cues on learning, suggest that such cues may constitute a necessary component of language input.

Word-level information influences phonetic learning in adults and infants

Infants begin to segment words from fluent speech during the same time period that they learn phonetic categories. Segmented words can provide a potentially useful cue for phonetic learning, yet accounts of phonetic category acquisition typically ignore the contexts in which sounds appear. We present two experiments to show that, contrary to the assumption that phonetic learning occurs in isolation, learners are sensitive to the words in which sounds appear and can use this information to constrain their interpretation of phonetic variability. Experiment 1 shows that adults use word-level information in a phonetic category learning task, assigning acoustically similar vowels to different categories more often when those sounds consistently appear in different words. Experiment 2 demonstrates that 8-month-old infants similarly pay attention to word-level information and that this information affects how they treat phonetic contrasts. These findings suggest that phonetic category learning is a rich, interactive process that takes advantage of many different types of cues that are present in the input.

Prosody and the Roots of Parsing

Representing input utterances in structurally appropriate fashion is doubly important for naive language learners: Learners need to parse utterances both to generate immediate suitable interpretations and to provide bases for inducing syntactic patterns or setting grammatical parameters so that future utterances can be appropriately represented and interpreted. Many of the powerful tools used for parsing by mature speakers, however, are unavailable to infants at the outset of language learning. Possessing only meagre lexicons and rudimentary grammars, infants must begin to carve words from continuous speech, assign words to appropriate grammatical categories, and determine how words group into phrases through largely bottom-up analyses of input. Research presented in this paper on the character of infant-directed speechand the nature of infant speech perception abilities from 6 to 12 months strongly suggests that prosody, in conjunction with other forms of phonological information available in input speec...