The Development of Speech Perception: The Transition from Speech Sounds to Spoken Words

240 Pages·1994·1.24 MB·English

by  Judith C. Goodman

The Development of Speech Perception:
The Transition from Speech Sounds to Spoken Words
Edited by
Judith C. Goodman and
Howard C. Nusbaum
A Bradford Book
The MIT Press
Cambridge, Massachusetts
London, England

title: The Development of Speech Perception : The Transition
From Speech Sounds to Spoken Words
author: Goodman, Judith
publisher: MIT Press
isbn10 | asin: 0262071541
print isbn13: 9780262071543
ebook isbn13: 9780585021256
language: English
subject Language acquisition--Congresses, Speech perception--
Congresses, Perceptual learning--Congresses.
publication date: 1994
lcc: P118.D46 1994eb
ddc: 401/.93
subject: Language acquisition--Congresses, Speech perception--
Congresses, Perceptual learning--Congresses.
cover
© 1994 Massachusetts Institute of Technology
All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means
(including photocopying, recording, or information storage and retrieval) without permission in writing from the
publisher.
This book was set in Times Roman by Asco Trade Typesetting Ltd., Hong Kong, and was printed and bound in the
United States of America.
Library of Congress of Cataloging-in-Publication Data
The Development of speech perception: the transition from speech sounds to spoken words/ edited by Judith Goodman
and Howard C. Nusbaum.
p. cm.(Language, speech, and communication)
Papers presented at the Workshop on Recognizing Spoken Language which was held June 1989, University of Chicago.
"A Bradford book."
Includes bibliographical references and index.
ISBN 0-262-07154-1
1. Language acquisitionCongresses. 2. Speech perceptionCongresses. 3. Perceptual learningCongresses. I. Goodman,
Judith, 1958 II. Nusbaum, Howard C. III. Workshop on Recognizing Spoken Language (1989: University of Chicago) IV.
Series.
P118.D46 1994
401'.93dc20 93-11391
CIP

cover-0
Contents
Preface vii
Contributors xi
Introduction 1
Chapter
1 Developing Theories of Speech Perception: Constraints from Developmental Data 3
Judith C. Goodman, Lisa Lee, and Jenny DeGroot
Part I Innate Sensory Mechanisms and Constraints on Learning 35
Chapter
2 Observations on Speech Perception, Its Development, and the Search for a Mechanism 37
Joanne L. Miller and Peter D. Eimas
Chapter The Importance of Childhood to Language Acquisition: Evidence from American Sign
3 Language 57
Rachel I. Mayberry
Part II Perceptual Learning of Phonological Systems 91
Chapter
4 Cross-Language Speech Perception: Developmental Change Does Not Involve Loss 93
Janet F. Werker
cover-1
Page vi
ChapterPerceptual Learning of Nonnative Speech Contrasts: Implications for Theories of Speech
5 Perception 121
David B. Pisoni, Scott E. Lively, and John S. Logan
ChapterThe Emergence of Native-Language Phonological Influences in Infants: A Perceptual
6 Assimilation Model 167
Catherine T. Best
Part III Interactions of Linguistic Levels: Influences on Perceptual Development 225
Chapter
7 Infant Speech Perception and the Development of the Mental Lexicon 227
Peter W. Jusczyk
ChapterSentential Processes in Early Child Language: Evidence from the Perception and Production
8 of Function Morphemes 271
LouAnn Gerken
Chapter
9 Learning to Hear Speech as Spoken Language 299
Howard C. Nusbaum and Judith C. Goodman
Index 339

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Preface
Traditionally, theories of speech perception have sought to explain primarily the way adults recognize spoken language,
seldom considering the problem of the way this ability develops. Of course, any theory of speech perception must
account for performance by mature language users, but our goal in developing this book was to encourage researchers to
consider the proposition that theories must also account for the development of linguistic processing and the changes that
occur with maturation and experience.
Although developmental questions have been addressed in speech research, this work initially focused on the way speech
perception develops in prelinguistic infants. Several researchers have asked how innate abilities interact with perceptual
experience over the course of the first year of life, but it is important to expand this focus to allow an examination of the
role of developing linguistic knowledge and increasing experience using language in understanding the way speech
perception develops. Perceptual processing may be modified when children begin to learn their native phonologies and
lexicons, as well as higher levels of linguistic structure, and research on very young infants alone fails to capture this sort
of development.
Indeed, the chapters in this volume report that changes related to the acquisition of linguistic knowledge do occur. While
the contributors to this volume do not all agree on the specific nature of the processes involved in speech perception or
the way in which these processes develop, together, these chapters document the striking changes that take place, not
only in early childhood but throughout life. In addition, the authors use these findings to make suggestions as to how
theories of speech perception will need to be modified if they are to explain such changes.
This volume grew out of the Workshop on Recognizing Spoken Language that was held at the University of Chicago in
June 1989. The goal

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of this workshop was to examine transitions in the perceptual processing of speech from infancy to adulthood. The
workshop participants were scientists who have carried out speech research with infants, children, and/or adults. Their
task was to consider in detail the theoretical implications of their research for a well-specified and complete theory of
speech perception that could address issues concerning speech perception in children and adults, as well as the
development of those abilities. In particular, the participants were invited to speculate about how their findings constrain
the nature of the mechanisms and representations that mediate speech perception during infancy, childhood, and
adulthood.
This is a tall order, and these chapters contain a wealth of information on the development of perceptual processing, as
well as constraints and prescriptions for the development of theories of perceptual processing. The findings reported here
cover many critical issues for theory buildingfor example, how maturation and experience modify innate sensory
mechanisms, how structural knowledge is acquired, whether young children represent linguistic information in the same
way as adults, and how segment- and word-recognition processes differ among children and adults. In addition, they
include proposals regarding the nature of the mechanisms behind the perception of linguistic units, the acquisition of
early word patterns, and the development of the mental lexicon.
This book differs from previous books on speech perception in several respects. First, it attempts to integrate research
involving infants, young children, and adults. Although in recent years several books have considered a wide range of
issues in speech perception, these books have not thoroughly addressed developmental issues; at best they have included
only one or two chapters on speech perception in infants. Second, this book tries to explore systematically how adult
perceptual abilities develop from early infant capabilities, focusing in particular on the nature of the transitional stages
and the constraints they place on theories of speech perception. Other recent books on speech perception that have
focused on a single theoretical issue have not addressed the transition from recognition of speech segments to recognition
of spoken words. Finally, unlike other books that have addressed issues in perceptual development, this book also focuses
on speech perception. We hope that researchers and students in the areas of psychology, linguistics, cognitive science,
and speech and hearing will find this approach stimulating.
We are deeply grateful to the authors who contributed to this volume. We appreciate their level of commitment, their
willingness to go beyond their data to make theoretical speculations, and their patience during both

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the workshop and the preparation of the book. We are grateful to Dr. John Tangney and the Air Force Office on Speech
Research (grant no. AFOSR 89-0389) and to the Council on Advanced Studies in the Humanities and Social Sciences at
the University of Chicago for financial support to conduct the Workshop on Recognizing Spoken Language. Several
graduate students made the preparation for the workshop much smoother; they include Kevin Broihier, Anne Farley,
Jenny DeGroot, and Lisa Lee. In addition, several colleagues and students participated in the workshop discussions,
enriching the experience for everybody. We thank Jenny DeGroot, Starkey Duncan, Susan Duncan, Anne Farley, Steve
Goldinger, John Goldsmith, Beth Greene, Janellen Huttenlocher, Karen Landahl, Lisa Lee, Susan Levine, Jerre Levy,
David McNeill, Todd Morin, Nancy Stein, and Michael Studdert-Kennedy for their participation. We wish to express
special thanks to Anne Cutler for her valuable contributions to the workshop. Jennifer Jahn assisted in preparation of the
manuscript. We express gratitude to Teri Mendelsohn, our editor at the MIT Press, for her patience and guidance.

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Contributors
Catherine T. Best Department of Psychology, Wesleyan University, Middletown, CT; Haskins Laboratory, New Haven,
CT
Jenny DeGroot Department of Psychology, University of Chicago, Chicago, IL
Peter D. Eimas Department of Cognitive and Linguistic Sciences, Brown University, Providence, RI
LouAnn Gerken Department of Psychology, State University of New York at Buffalo, Buffalo, NY
Judith C. Goodman Department of Psychology, University of California at San Diego, La Jolla, CA
Peter W. Jusczyk Department of Psychology, State University of New York at Buffalo, Buffalo, NY
Lisa Lee Department of Psychology, University of Chicago, Chicago, IL
Scott E. Lively Department of Psychology, Indiana University, Bloomington, IN
John S. Logan Department of Psychology, Carleton University, Ottawa, Ontario, CANADA
Rachel I. Mayberry School of Human Communication Disorders, McGill University, Montreal, Quebec, CANADA
Joanne L. Miller Department of Psychology, Northeastern University, Boston, MA
Howard C. Nusbaum Department of Psychology, University of Chicago, Chicago, IL

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David B. Pisoni Department of Psychology, Indiana University, Bloomington, IN
Janet F. Werker Department of Psychology, University of British Columbia, Vancouver, B.C., CANADA

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Page 1
Introduction

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Chapter 1
Developing Theories of Speech Perception: Constraints from Developmental Data
Judith C. Goodman, Lisa Lee, and Jenny DeGroot
A tremendous proportion of research in speech perception has focused on a listener's ability to identify or discriminate
phonetic contrasts. This focus on lower-level segmental perception until recently dominated research with both adults
and infants (Eimas et al. 1971; Mattingly et al. 1971; Pisoni 1973; see also Aslin, Pisoni, and Jusczyk 1983 for a review
of segmental perception abilities by infants). As a result of this focus and the sorts of data these studies provide,
theoretical questions have addressed whether the mechanisms responsible for speech perception are best described as
innate and speech specific (Liberman et al. 1967; Liberman and Mattingly 1985; Repp 1982) or as properties of the
general auditory system (Lane 1965; Pastore 1981; Pisoni 1977).
The chapters in this volume suggest that either characterization alone is too narrow because they have concentrated on
studying perception in stable periods rather than trying to explain developmental change. By focusing on questions
regarding change in the processes of language perception across the lifespan, however, it can be seen that infants have
innate perceptual biases that are shaped by subsequent experience. Further, it appears that many levels of linguistic
structure provide informative constraints on one another (cf. Gerken, this volume; Jusczyk 1985; Katz, Baker, and
MacNamara 1974; Menn 1983 for discussions of the role of word learning in phonological development and semantics
and syntax in word learning) and that young listeners must learn about each level and how they may be related in
language processing. In addition, these developmental lessons appear to be useful in explaining language processing and
perceptual learning in mature listeners as well.
Our goal in this chapter is to abstract from the set of papers in this volume broad themes that must be considered in
explaining the development of speech perception and language understanding. These themes, on

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the whole, are concerned with the nature of linguistic experience and its influences on perceptual development.
Historically, research in speech perception dealt with how adults identify and discriminate phonetic information in the
acoustic input. This focus on adults is not surprising because what investigators sought to explain was the end statethat is,
how the mature listener perceived linguistic information. A challenge for these theories was to explain how listeners
handle the lack of invariance in the speech stream: no one-to-one mapping exists between information in the acoustic
waveform and the listener's percept. Many theorists proposed innate, speech-specific mechanisms to account for this fact
(Liberman et al. 1967; Liberman and Mattingly 1985; Repp 1982). In order to evaluate that claim, developmental data
was required, and the discrimination abilities of young infants were assessed. Still, it was not immediately apparent that
any developmental change in speech perception occurs because much of the early work found that very young infants
possess discrimination and identification abilities that are remarkably similar to those of adults (Eimas et al. 1971; Kuhl
1979; see Aslin, Pisoni, and Jusczyk 1983; Jusczyk 1981 for reviews).
This path of research has resulted in a gap between our knowledge of the infant's early sensory abilities and the adult's
processing of speech. We know that prelinguistic infants are sensitive to acoustic information which is linguistically
relevant and that there are striking similarities between their sensitivities and those of adults on tasks that involve the
discrimination of discrete, phonetic segments. But we also know that children come to represent linguistic unitsthat is,
they not only discriminate phonetic contrasts but they develop, for example, phone categories and lexical knowledge as
well. In other words, despite the perceptual parallels that exist between very young infants and adults, speech perception
does undergo development, and a theoretical account of the transition from the infant's sensory capacities to the child's
ability to identify words and perceptual learning by adults must be provided.
The chapters in this volume detail the changes that occur and propose mechanisms by which innate prelinguistic
discriminatory abilities may come to handle the representation and perception of linguistic structures. Further, many of
the changes we see during early childhood appear to have parallels in the processing of speech input by adults. Hence, the
mechanisms responsible for the development of speech perception may play a role in processing throughout the lifespan
and, therefore, may be important factors in explaining speech perception. This is not to claim that no differences exist
between children and adults. They do, and they

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must be explained. Nonetheless, the similarities are very suggestive about what sorts of mechanisms affect both
perceptual learning and the identification of linguistic units.
Due to the recent wealth of information concerning the nature of developmental change in language processing, it should
be possible to narrow the gap that exists between our theories of the innate processing mechanisms of infants and of
adults' abilities to recognize discrete linguistic units. The parallels noted above highlight the possibility of developing a
single, coherent theory of speech perception to account for the abilities of children and adults rather than having a
collection of theories each accounting for the perceptual abilities of a single age group.
This has not generally been the case. Most theories of adult speech perception do not consider how perceptual
mechanisms and linguistic representations develop (Elman and McClelland 1986; Liberman et al. 1967; Liberman and
Mattingly 1985). However, an understanding of developmental changes in the nature of these mechanisms and
representations could constrain theories of how adults use knowledge about structural properties of phonemes and words
to mediate language recognition. Therefore, in constructing theories of speech perception, it is important to consider how
maturation and experience modify innate sensory mechanisms, how structural knowledge is acquired, and whether young
children represent linguistic information in the same way as adults.
Similarly, studies of infant speech perception have seldom attempted to explain fully how the ability to recognize words
develops from innate perceptual abilities (but see Jusczyk 1985; Studdert-Kennedy 1986). A complete theory of speech
perception must describe how innate perceptual mechanisms come to support recognition of consonants and vowels as
phonetic categories, as well as the role of phonetic categories in the acquisition of early word patterns and the
development of the mental lexicon. Finally, theories of vocabulary acquisition in early childhood (Clark 1983; Markman
1991) and word recognition in middle childhood (Tyler and Marslen-Wilson 1981) are rarely linked to the infant's innate
perceptual abilities or to lower-level segmental processing at any age. In short, there is a need to integrate the findings
and conclusions of speech research from early perceptual encoding in infants to word recognition in adults.
While a great deal of work remains before a theoretical integration of this sort can be accomplished, we hope to further a
consideration of what a coherent theory might include by detailing factors that influence the development of speech
perception. We are not attempting to provide

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a theory, but we wish to highlight issues raised by the contributors to this volume that may shed light on the perceptual
processing of speech throughout the lifespan.
Three issues seem particularly important for building a theory of speech perception. The first of these issues concerns the
relationship between levels of linguistic knowledge in processing. A language is a multileveled system for
communication supporting the production and perception of phonemes, words, syntax, and paralinguistic information,
such as prosody. Information at one level may serve to constrain learning and perception at another level. For example,
children's phonological knowledge may emerge from their early lexical development (Menn 1983). Data concerning the
processes involved in understanding linguistic information at one level of representation may constrain the types of
processes that operate at other levels of representation. The chapters in this volume suggest that we should construe our
notion of level of linguistic structure or knowledge quite broadly indeed. Hence we will consider the role of stress and
prosody in the development of speech perception and the relationship between linguistic production and linguistic
perception, as well as processing interactions between levels of linguistic structure, such as the lexical and phoneme
levels. A consideration of data from both children and adults supports the conclusion that a theory of speech perception
should integrate the findings of research concerning language processing across levels of perceptuolinguistic analysis.
The second issue is concerned with the role of early linguistic experience. Early linguistic experience has two sorts of
effects. First, a critical period may exist for language learning (Lenneberg 1967), and, second, knowledge of one
language affects the learning and processing of a second language (Best, this volume; Best, McRoberts, and Sithole
1988; Lively, Pisoni, and Logan 1991; Logan, Lively, and Pisoni 1991; Pisoni, Lively, and Logan, this volume; Werker,
this volume; Werker and Lalonde 1988; Werker and Tees 1983). Something seems to be special about early childhood
with respect to language development. While some amount of perceptual learning is possible throughout the lifespan,
Mayberry's work shows that, if children are not exposed to linguistic input during the early years, subtle deficits exist
even after twenty years of language use (this volume; Mayberry and Eichen 1991; Mayberry and Fischer 1989). We will
consider the nature of this critical period and the sorts of developmental mechanisms that might account for it. One
possibility is that a critical learning period exists during which specialized neurological structures may be established for
perceptual processing of language. A second

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possibility is that it is easier to learn some aspects of linguistic structure in the absence of other higher-order knowledge
because the latter may focus one's attention at the wrong level of analysis (see Pisoni et al., this volume). Most people do,
of course, learn a first language in early childhood, and the knowledge of that language influences their ability to learn
and to process a second language. The chapters by Pisoni, Lively, and Logan; Werker; and Best show that limitations on
the perceptual learning of a second language exist as a result of phonological knowledge of a first language. In addition,
work by Cutler et al. (1989, 1992) and by Grosjean (1988, 1989) indicates that even bilinguals show limitations in
learning two languages.
The third issue concerns the role of attention in perceptual learning. Experience with language modifies perceptual
processing both for children (Best, McRoberts, and Sithole 1988; Kuhl et al. 1992; Werker and Lalonde 1988; Werker
and Tees 1983) and adults (Lively, Pisoni, and Logan 1991; Logan, Lively, and Pisoni 1991; Pisoni et al. 1982; Samuel
1977). Current theories of speech perception cannot account for the development of perceptual abilities, however,
because they do not include a mechanism of change as part of the perceptual process. Many chapters in this volume
suggest that dynamic mechanisms-that is, processing mechanisms that allow a listener to change what information is
attended to according to input propertiesare critical for theories concerning the recognition and comprehension of spoken
language (Best, this volume; Jusczyk, this volume; Mayberry, this volume; Nusbaum and Goodman; this volume; Pisoni,
Lively, and Logan, this volume; Werker, this volume). Dynamic mechanisms will be an important component of a theory
that accounts both for the way speech perception develops throughout childhood and for the way perceptual processes are
modified by adults. Many authors in this volume argue that perceptual learning involves shifting one's attention to
particularly informative aspects of the acoustic signal. In other words, the effect of experience with one's native language
or, later, with a second language is to learn how to direct attention to the acoustic, segmental, lexical, and sentential
properties of an utterance that work together to specify the linguistic interpretation of the utterance. Below we address the
evidence related to each of these issues.
Relationships between Levels of Linguistic Structure in Speech Perception and Language Understanding
Theories of word recognition have commonly incorporated the use of information from multiple linguistic levels (Elman
and McClelland 1986;

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Morton 1969; Marslen-Wilson 1975, 1987; Marslen-Wilson and Tyler 1980; Marlsen-Wilson and Welsh 1978) though
theories of speech perception seldom do (Liberman et al. 1967; Liberman and Mattingly 1985; Stevens and Blumstein
1981; Stevens and Halle 1967). However, several of the contributors to this volume, as well as other researchers, have
demonstrated interactions between levels of linguistic structure during language processing. Below, we look at the
interactions between phonemes, words, syntax, and prosody, as well as between perception and production. A single
coherent theory that explains processing and acquisition at a number of linguistic levels for a wide variety of input
contexts is needed to account for these findings.
Interactions between Different Levels of Linguistic Structure
In her chapter, Gerken notes that a common view about language acquisition is that children start with the smallest units
and gradually learn about larger and larger units as they acquire language. This seems intuitively plausible. After all, if
words are composed of phonemes, one must first learn phonemes, and if sentences are composed of words, then word
learning must precede sentence learning.
However, a great deal of research suggests that different levels of linguistic information are highly interactive both in
language acquisition and in language processing by children. A number of examples illustrate this point. Gerken (this
volume) suggests that syntactic information influences perception and learning at the lexical level in 2-year-olds. Recent
work by McDonough and Goodman (1993) finds that 2-year-olds use semantic information provided by a familiar verb
such as eats to assign meaning to an unfamiliar sound pattern such as rutabaga and that 2-year-olds' identification of an
ambiguous sound pattern in a sentence is influenced by semantic context (Goodman 1993). Lexical knowledge influences
phoneme perception by children: children's perception of ambiguous phonemes is influenced by lexical context (Hurlburt
and Goodman 1992). In addition, changes in phoneme perception occur around 10 months of age (Werker and Lalonde
1988; Werker and Tees 1983), suggesting that interactions may occur between the development of phoneme perception
and the acquisition of a child's earliest-comprehended lexical units. Finally, suprasegmental information influences
perception of other units: HirshPasek et al. (1987; see also Kemler Nelson et al. 1989) have shown that suprasegmental
information may direct infants' attention to linguistic units such as clauses and phrases. These findings are not raised to
make claims about temporal properties of interactive processing but to note

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that at some stage in processing (perceptual or postperceptual decision) information at one level affects identification and
acquisition at other levels of linguistic structure.
How can these sorts of interactions in acquisition and processing be explained? In his chapter, Jusczyk provides one
suggestion of how various levels of linguistic structure might interact to result in phonological learning. The model of
word recognition and phonetic structure acquisition (WRAPSA) that Jusczyk presents suggests that children do not work
up unidirectionally from smaller to larger units. Jusczyk theorizes that young infants store exemplars of the utterances
they hear, perhaps represented in syllabic or larger units. With linguistic experience, they begin to weigh the properties of
the utterance according to their relative importance in signaling meaningful distinctions. Segmental representations arise
from the discovery of similarities and contrasts among these exemplars. Due to the temporal nature of speech (simply
put, the listener hears the initial portions of an item first), this process may be biased toward segments in initial position.
For example, utterances with initial segments that share acoustic characteristics may be classified together, forming the
basis for distinguishing these segments from other segments.
In her chapter, Best also speculates that infants' phone categories are not necessarily segmental in size but may involve
larger units such as syllables and words. Phonological knowledge may arise from a refinement of these larger units.
Best's view of what information is important in signaling meaningful distinctions between phone categories differs from
that suggested by Jusczyk. In particular, she suggests that infants come to represent phone categories by learning the
articulatory-gestural properties of speech. According to this view, both speech perception and production are guided by
knowledge of articulatory gestures.
Although the details of these models may not all be correct, the models attempt to deal with a void in theories of speech
perception, namely the mechanisms by which infants hone in on the phonology of their native language. Whatever the
nature of phoneme representations, an integration of levels of linguistic structure may be critical in learning the relevant
categories because it provides important constraints on the identity of acoustic information. Thus, the acquisition of a
lexicon might contribute to the categorization of speech because it is informative with respect to the correlations of
distributional properties that signal meaningful distinctions (for example, phonemes distinguish words).
The same kind of interactive constraint process may operate at other levels of linguistic structure. For example,
suprasegmental information in

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English may signal the onset of a word (Cutler et al. 1992). This issue is important in accounting for perception in adults
as well as children. Pisoni, Lively, and Logan (this volume) show that perceptual learning occurs in adults and is affected
by the position in a word where the phoneme occurs. Ganong (1980) found that lexical information affects phoneme
perception in monolingual adults, and Grosjean (1988; Burki-Cohen, Grosjean, and Miller 1989) found that, under certain
conditions, phoneme perception by adult bilinguals is affected by the language of the surrounding words.
To note the role of higher-level information in perceptual learning does not preclude the simultaneous occurrence of
within-level learning. For example, infants may develop vowel categories prior to any knowledge of word level
information. Kuhl et al. (1992) tested infants from the United States and Sweden on their perception of native- and
foreign-language vowel prototypes. Their results showed that by 6 months of agebefore they have acquired wordsinfants
have become sensitive to vowels that are prototypical of their native language. These vowel categories may emerge not
from the acquisition of words but from the way infants are predisposed to store information. Nonetheless, interactions
between different levels of linguistic knowledge play an important role in other sorts of perceptual development, and any
theory of speech perception must provide an account of these interactions.
Stress and Prosody
Although language development is most often studied in terms of growing knowledge of segmental units of various
sizes, such as phonemes, morphemes, and words (Bates, Bretherton, and Snyder 1988; Ferguson and Farwell 1975;
Menyuk and Menn 1979; Walley, Smith, and Jusczyk 1986), the suprasegmental level of linguistic information also
contributes to speech perception and its development. Suprasegmental information includes the patterns of stress and
prosody that are characteristic of a language. A growing body of research suggests ways in which stress and prosody are
important for language processing. Listeners use this information to interpret language and to learn more about the
structure of speech.
The prosodic structure of language can guide adult listeners in their perception of speech. Cutler (1976) showed that the
stress contours of an utterance focus a listener's attention on the location in a sentence of important semantic information.
Thus, prosodic information influences word identification by directing a listener's attention to particular items in an
utterance.

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More recently, Cutler and her colleagues (Cutler et al. 1986, 1989, 1992; Cutler and Norris 1988) have shown that
prosody can play a role in lexical segmentation for speakers of languages in which it is a predictable cue to word
boundaries. For example, English is a stress-timed language comprised of sequences of strong and weak syllables. Strong
syllables are more likely to signal the beginning of a content word than are weak syllables. French has a very different
prosodic structure; speech rhythm is syllable based. Cutler and her colleagues have found that English and French
listeners adopt different segmentation strategies that reflect the rhythmic structure of their respective languages. Native
English listeners segment the speech at strong-syllable boundaries, thus increasing the likelihood of finding and accessing
a content word (Cutler and Norris 1988). Native French listeners, however, use a syllable-based strategy (Cutler et al.
1986, 1989). Thus, prosodic features affect perceptual processing. Further, since they affect processing in language-
specific ways, they must be learned.
In addition to highlighting word boundaries and semantic information for adult listeners, prosodic variables may play a
role in the development of language recognition and language production. Many researchers have provided evidence that
stress patterns affect early lexical development (Blasdell and Jensen 1970; du Preez 1974; Gleitman and Wanner 1982;
Slobin 1982): stressed words may stand out in a stream of fluent speech. In other words, they may be easier to segment
from the speech stream. This hypothesis is supported by the fact that content words, such as object names, which tend to
receive primary stress, tend to be learned early (Nelson 1973). Although it is plausible that children fail even to perceive
words in an utterance that do not receive stress, it is more probable that, like adults, stress simply directs them to the
important semantic information. Gerken's work (this volume) demonstrates that children do, in fact, perceive unstressed
items. Although they apparently recognize these items, they often fail to produce them in their own utterances. But, even
their omissions demonstrate their sensitivity to and knowledge of the prosodic patterns of English: when utterance
complexity causes children to omit words from their speech, they follow the metrical pattern of English, producing words
in strong positions and omitting weak syllables that follow them. This suggests that young children know a great deal
about the prosodic patterns of sentences.
In fact, even before children begin to understand spoken language, they are sensitive to the prosodic properties of speech
that facilitate perception. In a series of experiments, Kemler Nelson et al. (1989) suggest how sen-

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tence prosody may provide cues to segmentation of linguistic units, such as clauses and phrases. Kemler Nelson et al.
(1989), for example, found that 6-month-old infants are sensitive to the prosody of clausal units. The infants heard
speech samples in which one-second silences were inserted either at clause boundaries or in the middle of clauses. The
investigators hypothesized that the sentences with silence inserted at clause boundaries would sound more natural. The
infants preferred the more natural utterances, suggesting that they are sensitive to the relationship between prosody and
linguistic units.
At nine months, infants preferred speech in which silences were inserted between syntactic phrases than speech in which
silences were inserted within phrases. These findings held even when the phonemic content was filtered out of the