Haskins Laboratories Status Report on Speech Research1992, SR·111/112, 89·102

Gestures, Features and Segments in Early Child Speech*

Michael Studdert-Kennedy and Elizabeth Whitney Goodell

Alphabetic orthographies represent speech at the level ofthe phoneme. Yet the definitionand functional status of the phonemic segment are widely viewed as problematic. Studiesof child phonology have shown that the initial domain of a child's articulatory organizationis the word rather than the segment, and have attributed a child's errors to failure toorganize the features of a target word. The paper rejects the feature, as a unit ofarticulatory organization, on both rational and empirical grounds, proposing in its steadthe gesture. Evidence from a child (1;9-2;1) learning American English shows how deviantforms, puzzling for a featural account, are readily explained as errors in the execution andtiming of gestures. Phoneme-sized phonetic segments are then viewed as emergentproperties of the gestural routines from which the child constructs its lexicon.

INTRODUCTION

PreliminaryThat an alphabetic orthography represents

speech at the level of the phoneme seems to begenerally agreed. But the definition of thephoneme, and even its functional status, are stillmatters of contention among linguists. We do notpropose to join the linguistic argument here. Wetake the facts of reading and writing to besufficient evidence for the functional reality of thephoneme as a perceptuomotor control structurerepresenting a class of phonetic segments (cf.Studdert-Kennedy, 1987). We assume, further,that phonetic segments (consonants and vowels)are not the irreducible elements of which speech iscomposed. Rather, segments are complex struc­tures, implicit in the gestural patterns of speech,that gradually emerge and take on their percep­tuomotor functions over the first few years of life.

Some of the data reported here were first presented at theFifth International Congress for Child Language, Budapest,July 1990. We thank "Emma" and her family for their cheerfulcooperation; Cathe Browman, Charles Ferguson, LouisGoldstein, Marlys Macken, Lise Menn, Elliot Saltzman,Marilyn Vihman and Natalie Waterson for the insights wehave gained from their papers; Catherine Best, CatheBrowman, Ignatius Mattingly and Natalie Waterson for theirinstructive comments; Zefang Wang for assistance with thefigures. The research and the preparation of this paper weresupported, in part, by NIH grants to Haskins Laboratories,HD-01994 and NS-24655.

89

The present chapter attempts to justify this claimby applying a developing theory of articulatoryphonology (Browman & Goldstein, 1986, 1989) toa small set of data drawn from the utterances of atwo year old child.

BackgroundA child, learning to talk, often says the same

word in several different ways. Indeed, variabilityof phonetic form has been a commonplace of childlanguage studies since their inception (e.g.,Albright & Albright, 1956, 1958; Cohen, 1952;Leopold, 1953). On the other hand, a child,learning to talk, often says several different wordsin the same way, and this homonymy is also acommonplace of child language studies (seeVihman, 1981 for review). While variability andhomonymy may reflect many factors, including thecommunicative situation, whether the utterance isspontaneous or imitated, its meaning, phoneticstructure, phonetic context, and so on (Schwartz,1988), none of these factors would matter, if itwere not that "...a child's phonemic system is inthe process of development, and the soundpatterning is probably less regular than that ofadult speech" (Albright & Albright, 1956:382). Butwhat, in fact, is developing, and what is thenature of the irregularity? What varies in theexecution of a target word from one occasion toanother? What does the child find that differentwords have in common?

90 Studdert-Kennedll and Goodell

Let us begin with the observation, now sup­ported by a variety of evidence, that the unit ofphonological contrast, and therefore the unit ofarticulatory organization, in early child speech isthe whole word or phrase rather than the segment(Ferguson, 1963, 1986; Ferguson & Farwell, 1975;Goodell & Studdert-Kennedy, 1991, in press;Macken, 1979; Menu, 1983; Menyuk, Menn, &Silber 1986; Nittrouer, Studdert-Kennedy, &McGowan, 1989; Waterson, 1971). To say that achild utters a word as a "whole," or Gestalt,cannot mean, however, that the child has notbroken the word into at least some of its parts,because even a partly correct utterance requirescoordination of independent, or partiallyindependent, actions of lips, tongue, jaw, velumand larynx. Accordingly, while the word may bethe domain over which a child organizes itsarticulations, it cannot be the basic unit ofproduction (or, a fortiori, of perception). Nor, sincethe segment is no less compounded of independentarticulatory actions than the word, can the basicunit be the segment itself.

The standard unit adopted in studies of childphonology is, of course, the feature. By this wecannot mean the abstract feature of generativephonology, a relational property fulfilling thelinguistic function of contrast across aphonological system, because we are dealing witha child for whom such a system does not yet exist.We must therefore mean the concrete feature, anabsolute property located "...within the speechsounds, be it on their motor, acoustical or auditorylevel" (Jakobson & Halle, 1956, p.8). However, atleast two facts make this proposal unacceptable.First, the feature has no independent existence: itis a property of a larger unit and is carried intoexistence on that unit, as an adjective, not a noun(cf. Fowler, Rubin, Remez, & Turvey, 1980). Thisfact is implicit in the adjectival terminology of allfeature theories: grave, acute, compact, coronal,nasal, strident, and so on.

A second, closely related objection is that theproperties to which featural terminology custom­arily refers are purely static, devoid of temporalextension, and therefore intrinsically unfit to de­fine the dynamic properties of speech either as amotor act or as an acoustic signal. Not surpris­ingly, none of several sets of acoustic and articula­tory definitions of phonological features (e.g.,Chomsky & Halle, 1968; Jakobson, Fant, & Halle,1951/1963; Stevens, 1972, 1975, 1989) has provedprecise or full enough to support a procedure forspeech synthesis or speech recognition by ma­chine, let alone a theory of speech production or

speech perception.! The "autonomous features" ofautosegmental and other forms of non-linearphonology (e.g., Clements, 1985; Goldsmith, 1990;McCarthy, 1988; cf. Menn, 1978) might seem topromise a solution. However, these features areabstract units, the temporal analogs of points inEuclidean space, admitting of sequence, but not ofextension. In short, as Ladefoged (1980:485) hasremarked, "... phonological features are certainlynot sufficient for specifying the actual sounds of alanguage." They can hardly therefore serve theturn of a child striving to learn how to perceiveand produce those sounds.

Very much the same holds for the informal, andperhaps intuitively more appealing, phonetic fea­tures adopted by, for example, Waterson (1971,p.183; cf. Ferguson & Farwell, 1975; Macken,1979). She analyzes a child's word forms into:"Various features of articulation, such as nasality,sibilance, glottality, stop (complete closure), con­tinuance, frontness, backness, voicing, voiceless­ness, labiality, rounding, non-rounding." Watersongoes on to group the child's forms into "structures"or "schemata", corresponding to the adult"prosodic" patterns in which features aredistributed over a word. She shows how in achild's utterance the "prosody" may be disrupted,so that features lose their temporal order andrecombine into patterns quite unlike the adultmodel. In this respect, Waterson's work hasstimulated the approach taken in the presentpaper. Nonetheless, her schemata are purelydescriptive, indications of, but certainly notspecifications for, the spatio-temporal pattern ofmovements by which a speaker, child or adult,executes a word. They offer, at most, a sketch ofthe high points of a word, rendered in the familiarlanguage of traditional articulatory phonetics. Weconclude that, despite the utility of the feature asa descriptive and classificatory element inphonetic theory, it cannot guide a child intospeech.

In fact, what a child quite evidently needs, toimitate an adult word, is a grasp on whicharticulators to move where and how, and on whento move them. And what we, for our part, need, tounderstand the child's attempts, is a description ofthe target word in terms of the units ofarticulatory action, and their relative timing,necessary to utter it. No generally agreed upon setof articulatory units exists, although several havebeen proposed. Ladefoged (1980), for example,offered a tentative list of 17 "articulatoryparameters" that he judged necessary andsufficient to specify the sounds of a wide range of

Gestures, Features and Segments in Early Child Speech 91

languages, but he did not develop them into afunctional model. Here we adopt the framework ofthe most explicit model of speech productioncurrently available, the gestural phonology beingdeveloped by Browman, Goldstein, Saltzman andtheir colleagues at Haskins Laboratories(Browman & Goldstein, 1986, 1987, 1989, 1990;Saltzman, 1986; Saltzman & Munhall, 1989), inwhich the basic phonetic and phonological unit isthe gesture. We illustrate the approach with asmall set of data, drawn from the utterances of a21-25 month old girl, learning American English.But before we come to the data we must give abrief sketch of the gestural framework.

Gestures as basic units of articulatoryaction

If we watch, or listen to, someone speaking, wesee, or hear, the speaker's mouth repeatedlyclosing and opening, forming and releasing

constrictions. In the framework of gesturalphonology, each such event, each formation andrelease of a constriction, is an instance of agesture. Constrictions can be formed within theoral, velic or laryngeal articulatory subsystems;within the oral subsystem, they can be formed bythe lips, the tongue tip (blade) or the tongue body.The function of each gesture, or act of constriction,is to set a value on one or more vocal tractvariables that contribute to the shaping of a vocaltract configuration, by which (in conjunction withpulmonic action) the flow of air through the tractis controlled, so as to produce a characteristicpattern of sound. Presumably, this pattern ofsound specifies for a child (or an adult) the gesturethat went into its making.

Figure 1 displays the tract variables and theeffective articulators of a computational modelfor the production of speech, at its current stageof development (Browman & Goldstein, 1990).

tract variable articulators involved

lP lip protrusion upper & lower lips, jawlA lip aperture upper & lower lips, jaw

TTCl tongue tip constrict location tongue tip, tongue body, jawTTCD tongue tip constrict degree tongue tip, tongue body, jaw

reCl tongue body constrict location tongue body, jawreCD tongue body constrict degree tongue body, jaw

VEL velie aperture velum

VEL~

_ GLO

velum

tonguebody

center

+ tongue root

glottis

+ upper lip

+ lower lip

jaw

Figure 1. Tract variables and associated articulators used in the computational model of phonology and speechproduction discussed in the text. (Adapted from Browman & Goldstein, 1990).

92 Studdert-Kennedu and Goodell

The inputs to the model are the parameters of setsof equations of motion for gestures. A gesture is anabstract description of an articulator movement,2or of a coordinated set of articulator movements,that unfolds over time to form and release acertain degree of constriction at a certain locationin the tract. Settings of the parameters permitconstriction degree to vary across five discretevalues (closed, critical, narrow, mid, wide), andconstriction location for oral gestures to varyacross nine values (protruded (lips), labial, dental,alveolar, postalveolar, palatal, velar, uvular,pharyngeal).3 The reader may observe that thedegree and location of an oral constriction roughlycorrespond to the manner and place of articulationof a segment in standard terminology.

The gestures for a given utterance are organizedinto a larger coordinated structure, represented bya gestural score. The score specifies the values ofthe dynamic parameters for each gesture, and theperiod over which the gesture is active. Figure 2(center) schematizes the score for the word nut([DAt)), as a sequence of partially overlappinggestural activation intervals; possible freevariation in the duration of the velic gesture, andthe resulting nasalization of the vowel, isindicated by extending the velic activationinterval with a dashed line.

We cannot here go into detail on the workings ofthe model (for which the reader is referred to thepapers cited above). We note only the followingfurther points that, taken with the precedingsketch, may suffice for an intuitive grasp on how agestural framework can contribute to anunderstanding of the nature and origin ofirregularities in a child's early words.

1. An instance of a gesture is an objective, ob­servable event. We can observe a gesture by ear,and this is the usual basis of both imitation and .phonetic transcription. We can observe a gestureby eye, either unaided, as in lipreading, or with x­ray cinematography. We can observe a gesture bytouch, as in the Tadoma method of speech percep­tion. Finally, we can observe a gesture by sensingour own movements. However, if gestures drawingon the same, or closely neighboring, neuromuscu­lar sets overlap in time (as, for example, in certainlingual gestures for the consonantal onset and vo­calic nucleus of a syllable), the individual gesturesmay merge, so that we can observe only the resul­tant of their vectors.

2. The articulator sets and their dimensionsgiven above are not exhaustive. For example,

the tongue root must ultimately be included in themodel to handle variations in pharynx width.Also, constriction shape will have to be included,to handle the tongue bunching, narrowing orhollowing, necessary in the formation of certaincomplex gestures (cf. Ladefoged, 1980). Even thedefinition of the gesture itself may have to berevised to permit independent control of theformation and release of a constriction.

3. A gesture is larger than the properties ofconstriction location, degree and shape thatdescribe it, but smaller than the segment. Severalindependent gestures are required to form asegment, syllable, or syllable string.

4. Each gesture has an intrinsic duration thatvaries with rate and stress. Correct execution ofan utterance requires accurate timing of thegesture itself, and accurate phasing of gestureswith respect to one another.

5. By adopting the gesture as a primitive ofarticulatory action we can predict what types oferrors children are likely, or not likely, to make intheir early attempts at adult words. To this topicwe now turn.

The gestural origins of errors in a child'searly words

Phonetically, speech emerges over the first yearof life from the lip smacks, tongue clicks and popsassociated with the vegetative processes of eatingand breathing, combined with the stereotypedvocalizations of cries and comfort sounds (Stark,1986), through the reduplicated syllables ofcanonical babble, into the brief strings ofphonetically contrastive elements that make upearly words. Articulatorily, the progression is acyclical process of differentiation and integrationby which the child moves toward finer modulationof individual gestures and more precise phasing oftheir sequence. (For a fuller account of thehypothesized developmental course, see Studdert­Kennedy, 1991 a, b.)

Here, two steps are of interest. First is theshift in gestural timing associated with theintegration of prebabbling oral and laryngealgestures into the canonical syllable, usuallyaround the seventh month (Holmgren, Lindblom,Aurelius, Jalling, & Zetterstrom, 1986; Koopmansvan Beinum & van der Stelt, 1986). Earliervocalizations, termed "marginal babble" by Oller(1980), are commonly longer than adult syllables,but display adult-like properties of resonance,intensity and fundamental frequency contour.

Gestures, Features and Segments in Early Child Speech

LIPS

TONGUE closed

TIP alveolar

TONGUE midBODY pharyngeal

:-- -- -- -------,VELUM wide

-------------GLOTTIS wide

[ 'd A n t

LIPS

93

TONGUETIP

TONGUEBODY

midpharyngeal

wideVELUM

GLOTTIS

[------------:.---_. ------------wide

LIPS

TONGUETIP

TONGUEBODY

[ In A

closedlabial

midpharyngeal

t

VELUM

GLOTTIS wide

:------------, wide

---------------------wide

I p ATime

m p

Figure 2. Schematic gestural score for the word nut ['IlAt], (center), and for nut as spoken by Emma in doughnut, ['dAnt],(top), and peanut, ['pAmp], (bottom). The extensions of the velie activation intervals by dashed lines indicate possiblefree variation in the duration of velie gestures.

94 Studdert-Kennedll and Goodell

Canonical babble is marked by integration of aresonant nucleus with rapid (25-120 ms) closinggestures at its margins to form a syllable withadult-like duration (100-500 ms) (Oller, 1986). Thecanonical syllable is the first step in theemergence of two major classes of oral gesture: thenarrow or complete constriction of consonants andthe wider constriction of vowels (cf. MacNeilage &Davis, in press).

The early canonical syllable is often, though notalways, one of a rhythmic, reduplicated string ofidentical syllables. Reduplication indicates firstthat the child may lack independent control of theclosing constriction at the margin and the widerconstriction at the nucleus of a syllable; second,that the child cannot easily switch gestures insuccessive syllables. The tendency to reduplicatemay continue for many months, or even years, asevidenced by the commonly reported harmony inearly words between consonants (Vihman, 1978)and vowels, and even within consonant-vowelsequences. The last is revealed, for example, bycertain children's preference for high front vowelsafter alveolar closures, for low back vowels afterthe relatively extensive jaw-lowering release oflabial closures (Davis & MacNeilage, 1990; cr.Jakobson, 1941/1968:29,50).

Integration of prebabbling gestures into thecanonical syllable is a necessary condition of asecond step: differentiation of the syllable intoindependent gestural components. Differentiationgives rise to what Oller (1980) terms "variegatedbabble" in which the consonant-like syllable onsetand the vowel-like nucleus, or both, differ insuccessive syllables. The process may begin soonafter, or even at the same time as, the onset ofcanonical babble, but typically comes topredominate in the fourth quarter of the first year,and continues over many months in both babbleand early words (Davis & MacNeilage, 1990;Vihman, Macken, Miller, Simmons, & Miller,1985).

Before we consider the types of error that a childmay make we should note that, although we shallappeal to similarity among gestures as the basis ofa child's confusions, we will not spell out thedimensions of similarity. In fact, we shalldeliberately avoid the question of whether thoseconfusions reflect an incomplete percept (underwhich we may include incomplete storage of thepercept in memory) or inadequate articulatorycontrol (under which we may include failure torecover stored motor commands from memory).Perhaps, indeed, there is no general answer to

this question: similar errors may reflect differentprocesses in different words and in differentchildren. Here we adopt a neutral stance. Wesuppose that learning the phonology of a languageis a matter both of learning to perceive theacoustic pattern that specifies a talker's gestures,and of learning to plan and produce that patternoneself. Both these processes can be a source oferror.

Differentiation itself has two aspects, each opento characteristic forms of error. First isparadigmatic differentiation among individualgestures. Possible errors here follow from failureto identifY or execute the location, shape or degreeof a gesture; in the limit, an error of degree (oramplitude) may yield complete omission. Thesecond aspect is syntagmatic differentiationamong gestures in a particular utterance. Possibleerrors here include gestural reduplication(harmony), errors of timing (duration and relativephasing, including metathesis), and errors ofamplitude or degree. The consonant-vowel (orvowel-consonant) harmony noted above may beviewed as a syntagmatic error arising fromincomplete differentiation of the syllable into itscomponent consonantal and vocalic gestures. Ourpurpose in what follows is to illustrate how theerroneous forms of a child's early words can beperspicuously described as arising from gesturalerrors such as these.

Method

The subject "Emma" is a second child, born inConnecticut to parents who had moved there fromVancouver, British Columbia. Emma's mother wasthe full time caregiver for the child. The secondauthor lived with the family before and during thestudy and spent several hours a day observingEmma at meals, watching her play with her olderbrother and interact with her parents, andoccasionally looking at picture books with her.One of these books (Richard Scarry's Best WordBook Ever) was a rich source of new words.

Audio recordings began when Emma had avocabulary of about 100 words, mostlymonosyllables understood primarily by her motherand brother. The size of her vocabulary wasassessed with the MacArthur CommunicativeDevelopment Inventory for Toddlers, and bymaternal report. In the ninety-first week hermean length of utterance (MLU) was 1.00 and atthe end of the study (week 106), 1.15. For theweekly audio taping sessions, lasting from 30minutes to an hour, she wore a wireless 831 Audio

Gestures, Features and Segments in Early Child Speech 95

Technical lapel microphone concealed in a vest.E.W.G. was present at all sessions and kept adiary of the subject's phonological development tosupplement the recordings.

To facilitate the transcription and analysis ofEmma's utterances, recordings of the sessionswere digitized on a VAX 780 computer, at a 20kHz sampling rate, to yield a total of some 950utterances of which the experimenter and acolleague independently transcribed roughly 250.Transcription followed the principles of theInternational Phonetic Association (1989), withsome elaborations according to the Stanfordsystem for transcribing consonants in childlanguage (Bush, Edwards, Edwards, Luckau,Macken, & Peterson, 1973). Each utterance wascoded as either spontaneous or imitated; anutterance was assumed to be spontaneous unlessit immediately followed the adult target; all theexamples reported in this paper were spon­taneous, unless otherwise indicated. We reportonly utterances on which the two transcribersindependently agreed. The transcriptions will begiven in square brackets, following the conventionfor adult phonetic segments. We emphasize thatour use ofphonetic symbols does not imply thatsegments were already established in the child asdiscrete units of perception and production. Aphonetic symbol is simply a convenient shorthandfor combinations of laryngeal, oral or velicgestures.

Results and DiscussionMany researchers have described how a child,

making the transition from reduplicated babble tovariegated speech, discovers a pattern thatroughly fits a fair number of adult words, and socan serve as a bridge into the leXicon. Thesepatterns, variously termed prosodic schemata(Waterson, 1971), canonical forms (Ingram, 1974),articulatory routines, programs, templates (Menu,1978, 1983), word patterns (Macken, 1979) orvocal motor schemes (McCune & Vihman, 1987)will be treated here as routinized gestural scores.(Much of our analysis will indeed follow the leadof Waterson (1971), Macken (1979), and,particularly, Menn (1978, 1983) whose attentionto the articulatory organization of a child'sutterances anticipates our own.) Gestural routinessupport both stereotypy (including homonymy)and variability in a child's early attempts atwords; they are of interest because the gesturalproperties common to a particular score and to thedifferent target words for which it is used revealthe scope of a child's gestural conflations.

StereotypyGestural routines in babble and word play.

During the sessions themselves Emma did notbabble much, but diary entries from the firstmonth of the study (weeks 91-94) often recordEmma's babbles while quietly playing.. Forexample:

(1) [o'bi:n'o'bim'o'bi:n](2) ['be:'d;:J'be:'d;:J'berd;.)'berd;.)]

These utterances happen to consist ofrepetitions of one of Emma's forms for elephant(['o'bin]) and playdough (['berd;:J]), but she chantedthe sequences in a sing-song, with no apparentcommunicative intent. Both utterances containthe alternating sequence of constrictions at thelips and at the alveolar arch that proved to beEmma's most productive gestural routine. (For anexample of another child, learning MexicanSpanish, with a similar routine, see Macken,1979).

Strings of similar alternations occasionallyoccurred in taping sessions over the same period:

(3) ['IllAtI:'IllAtIrIllAtI:](4) ['o'bu:'di:'o'bu:'di:'o'bu:'ku:ki:](5) ['werdo'wi:'do:merno'mi:'n;:J'mu:'ni:'mi:'ni:'mi:'ni:]

Emma repeatedly produced (3) in weeks 92 and93, elongating the final frication, as thoughsavoring the flow of air, and with no apparentreferent. (4) contains two of Emma's words (seeTable 1 for ['o'bu:'di:j), while (5) is a mixture ofapparent nonsense syllables and word forms (seeTable 2), but none of the objects to which thewords refer was present. In (4) she abruptly brokeoff her labial-alveolar chant when a cookie cameinto view. In (5) she seemed to be playing with thelocation and degree oflabial constriction ([w]-[m]),the degree of accompanying velie constriction ([w]­[m], [d]-[n]), and (in an apparent instance ofvowel-consonant harmony) the front-back locationof narrow constrictions at the syllable nucleusbefore an alveolar constriction ([i:]-[e:]-[u:j).

Table 1. Active use of the labial-alveolar routine as abridge into the lexicon.

New Words Adult Target Emma's Attempts

Cranberry ['krrenben] ['berbi] ['borberbi] ['o'burdi:]

Red Lights ['red'IOIts] ['werjOI] ['bE't90ItS]

Hippopotamus ['hlp;;l'pot;mlAs] ['o'pmz] ['hlpos]

96 Studdert-Kennedy and Goodell

Table 2. Words attempted by means of the labial­alveolar routine in weeks 91-94.

These examples illustrate the emergence ofgestural stereotypy in babble and word play. Theyalso illustrate the familiar, but important factthat a listener often cannot distinguish, byphonetic form alone, between syllables that arebabbled and syllables that should count as aword. 4 Despite the discontinuity of function thatJakobson (1941/1968) noted many years ago,babble and speech are formally continuous. 5 Anadequate account of the shift in function musttherefore posit units of action that can becomfortably engaged by both babble and speech.Phonemes, phonetic segments and features areunsuited to this task: they cannot properly beadopted for prelinguistic babble because they aredefined in terms of language and speech.Moreover, as already noted, segments are complexunits, customarily analyzed into their featuralpredicates, while features have no existenceindependently of the syllables and segments theydescribe. By contrast, the posited gesture is anintegral unit of action that can serve equally as aprimitive unit of both babble and speech.

Gestural routines as bridges into the lexicon. Achild who has discovered a gestural routine, suchas the labial-alveolar sequence described above,will often extend it to a surprisingly diversecollection of new words in which she recognizesthe appropriate pattern (Macken, 1979)-inEmma's case words as diverse as cranberry, redlights, and hippopotamus (Table 1). Thus in therecording session of week 92, Emma's mothershowed her a cranberry for the first time, repeated

Emma's attempts

* ['bu:'di:]* ['berd;}]

['berdi:]

['perdd]['Pd't;}]

['mernd]['memi:]['mu:'ni:][werdd][werdi:]

* ['o'mim]['o'bim]['o'pi:n]

* ['o'bu:'di:]

* Homonyms

Adult targets

berry, bird. boosterpillow, playdoughumbrella

peanutpuppet

tomatomedicinemoney

playdoughraisin

elephant, airplaneelephantairplane

Happy Birthday, cranberry,raspberry

the word and asked her to say it. First Emmaattempted the word with gestural harmony,repeating the labial closure of the second syllable,['berbi:], then she perfected the number of syllables,['borberbi:], finally she reverted to a three-syllablelabial-alveolar routine, ['o'bu:'di:], transposing thepostalveolar retroflex constriction of [r] into thealveolar closure of Cd]. She used this form forcranberry for approximately the next two months.(We may note, incidentally, that Emma hereadopted a tactic that recurred in her attempts atseveral other words, usually words of three ormore syllables: she lowered her jaw andsubstituted the wide vocalic gesture of [0] as a sortof place-holder for the initial syllable or syllables.)

In week 95, hearing her mother point out thered lights on the tape recorder, Emma sponta­neously attempted red lights as ['werjOl], and sec­onds later, without correction, as ['bet'eOlts]. Here,for [r], she first picked up the narrow constrictionat the protruded lips, but omitted the accompany­ing postalveolar retroflexion, giving [w], then fellback on full labial closure, giving [b]. The alveolarclosure for Cd] she omitted on the first attempt,while successfully executing the nearby palatalglide of fj] in place of [l]-a common shift in theexact location and shape of the gesture for [l] inearly speech (e.g., Vihman & Velleman, 1989). Onthe second attempt she achieved full alveolar clo­sure, but anticipated the glottal opening and criti­cal fricative constriction of final [ts], giving the se­quence [tel instead of [dl].

A final, more complicated example occurred inweek 101. Seeing a familiar picture of ahippopotamus, Emma spontaneously pronounced['opmz]. Here she substituted her favored widevocalic constriction for the first one or twosyllables. The remaining three or four syllablesshe collapsed into one, built around her labial­alveolar routine. For this she correctly executedthe labial closure and glottal opening of [p], aswell as the alveolar constrictions of medial [t] andfinal [s]. But she omitted the labial closure of em]and the glottal openings of [t] and [s]; she roughlyharmonized the syllable nucleus to the followingalveolar closure; and she erroneouslysynchronized alveolar closure for[t] with velieopening for em]. The outcome of these maneuverswas [pmz], a syllable composed of four apparentsegments, three of which do not occur in the targetword-a result difficult to understand if weassume segmental primitives, but readilyintelligible in gestural terms.

To Emma's spontaneous ['opmz] E.W.G. replied:"Oh, hippopotamus,» eliciting a form that Emma

Gestures, Features and Segments in Early Child Speech

had used on previous occasions: ['hlpas], repeatedfour times. Here, with the model freshly in mind,Emma recaptured the first syllable, but omittedthe second, as well as the medial alveolar andvelie gestures of the final three syllables whichshe collapsed into the bare routine of initial labialand final alveolar gestures.

These three examples illustrate Emma's activeuse of a routinized gestural score as an armature,or skeleton, around which to construct her articu­lation of words presumably otherwise too difficult,whether perceptually or motorically, to attempt.We have characterized the routine in terms ofrough gestural location, disregarding differencesin precise location and in degree or shape. Thus,we have treated [b/p/m] and [w] as equivalentlylabial in Emma's utterances, [dltln], m, [r], and [s]as equivalently alveolar. These equivalences arejustified by Emma's gestural alternations both inthe examples above and in her other uses of thelabial-alveolar routine to which we now turn.

A gestural routine as a source of homonyms.Table 2 lists the entire set of recorded words towhich Emma applied the labial-alveolar routine.Some of these were in Emma's repertoire beforethe study began (according to maternal report)and, with the exception of [-a'min], elephant, allwere recorded during the first month of the study.We have grouped them according to the similarityof their phonetic patterns, making clear that inaddition to the actual sets of homonyms, markedwith asterisks, there are several sets of near­homonyms (Emma's forms for pillow andumbrella, tomato and medicine, playdough andraisin, where each member of a pair differs fromthe other only in its final vocalic gesture). Thesehomonymous groups, clearly not semanticallybased, validate the proposed routine as a func­tional process in Emma's attack on the lexicon, bydrawing attention to gestural similarities amongtarget words that, at first glance, are quite dis­similar (cf. Vihman, 1981). Thus, we find alveolar[d] for [r] in berry, for [st] in booster, for [1] inpil­low and umbrella, for [s] in raisin. At the sametime, the labial grouping is justified by Emma'sown use of [b] and [w] for [pl] in playdough, of [p]and [m] for [pI] in airplane, of [w] for initial [r] inraisin, of [m] and [b] for [£] in elephant.

Several of these substitutions can, of course, beinterpreted in featural terms. However,substitution of the narrow labial constriction of[w] for [r] in initial position, but of full alveolarclosure for [r] in medial position, would not beexpected on a featural account, since a givensegment carries the same featural predicates

regardless of context, and so should be subject tothe same perceptual or motoric confusions. 6 Agestural account, on the other hand, predicts suchsyntagmatic errors precisely because it views thetask of learning to talk as quite largely one oflearning to coordinate gestures that may differ intheir articulatory compatibility (cf. Menn, 1983).We shall see further examples of contextualeffects in our discussion of variability.

Finally, we must remark another process,difficult for a featural account, and important toour later discussion: the tendency for gestures to"slide" along the time line (Browman & Goldstein,1987) into misalignment with other gestures,often giving rise to apparent segments not presentin the target word. We have already noted thisprocess in Emma's ['apmz] for hippopotamus. Here(Table 2) we find it in ['me:'n~], tomato, wherevelic lowering for [m] extends into the alveolarclosure for [t], yielding [n]; and in ['a'mun],elephant, airplane, where velic lowering for [n]slides into alignment with labial closures for [£] or[pl], yielding [m]. In these examples the effect is ofgestural harmony, and so may be due not only toan error of gestural phasing, but also to "...thedifficulty in planning and production of rapidchanges of articulation in a short space of time"(Waterson, 1972:13, cited by Menn, 1983:30). Ofcourse, this too is a form of timing error.

VariabilitySpontaneous variations. While a gestural

routine may afford a child initial access to difficultwords of similar gestural pattern, it cannot solveall the problems of gestural selection and phasingwith which the child must contend in movingtoward an acceptable pronunciation. Variabilitywithin the constraints of the routine is animportant part of this process.

For example, Emma's attempts at elephant in asingle session in week 91 included: ['a'bin],['am'bin], ['a'min], ['a'fin], and ['a'pin], all of whichare formed by combining her initial vocalic place­holder and her labial-alveolar constriction routinewith her favored medial vowel-consonantharmony. Yet within these limits she seemed to betrying to hit upon the exact location of the gesturefor labial [£], and the relative phasing of glottalopening for [f] and velic lowering for [n]. Sheexperimented with the timing of velic action againin her forms for raisin: ['we:'ni], ['wem'di], ['we:'di].And in ['be:'d~], ['we:'d~],playdough, she seemed tobe trying to simulate the labial alveolar sequencein the cluster [pI] by playing with the exactlocation and degree of labial constriction.

98 Studdert-Kennedy and Goodell

Further examples of variability within theconstraints of a stereotyped routine come fromEmma's attempts to execute the syllable ['nAt] inthe words doughnut and peanut. We might haveexpected these words to be relatively easy, thefirst because it calls for three harmonious alveolargestures, the second because it fits Emma's labial­alveolar routine, already well established whenshe met the word. But in fact they proved to bequite difficult, both overall and in their identicalfinal syllable in particular. This syllable elicitedvery different patterns in the two contexts-a typeof result, as we have already remarked, readilyintelligible on a gestural, but not on a featuralaccount of her errors.

Doughnut was introduced in week 92. Emma'sfirst attempts were ['du:'dAtJ] and ['do:'dAts]. Thefinal critical alveolar constrictions added apparentsegments not present in the model. They were notattempts at the plural, because she was given onlypart of a doughnut to eat and only heard the wordin the singular. Rather, they seem to haveresulted from a relatively slow release of [t],making the fricative portion of the release (Fant,1973:112) more salient. Steriade (1989) offers asimilar analysis for derived affricates, proposingthat they "...differ from stops in the quality oftheir release." Over the next 10 weeks Emma'sattempts at this word varied over forms as diverseas ['du:'dg] and ['du:n'dAnt]. The latter seems toresult from prolongation of the alveolar closure formedial [n] after velie release, giving an unwanted[d], combined with prolongation of the alveolarclosure for final [t] and a shift in (or harmoniousrepetition of) the medial velie gesture, giving theunwanted final cluster. Figure 2 (top) displays aschematic gestural score illustrating the timingerrors required to make the shift from ['nAt] to['dAnt], and Table 3 lists in chronological ordersome of the variations on nut in doughnut forcomparison with those elicited by peanut.

Emma encountered a peanut in a picture bookin week 94. Drawing appropriately on her labial­alveolar routine, she first tried ['perdg], omittingvelie action, and later that week, ['pe:n'tg), whereprolongation of the medial alveolar closure,combined with a shift in the timing of the finalglottal opening,relative to velie closure and thetongue body gesture, gives rise to an apparentshift in the ordering of the target consonant­vowel-consonant sequence-a result difficult toexplain in either segmental or featural terms. Inweek 96 she offered ['pi:'pAp], omitting the veliegesture and succumbing to labial harmony, and['pe:m'pump]. The latter, formally analogous to

['du:n'dAnt], doughnut, with its velie harmony,mistimed velie action and resulting unwantedsegments, is further complicated by thesubstitution of harmonized labial closures for thealveolar closures called for by the target, andproper to her routine. Figure 2 (bottom) illustratesthe errors of gestural location and timing requiredto make the shift from ['nAt] to ['pAmp].

Table 3. Spontaneous variability within and betweenwords: The same target syllable executed differentlyindifferent phonetic contexts. The utterances are listedchronologically, but the columns for doughnut andpeanut are not synchronized.

Nut as in doughnut and peanut

doughnut ['do:nAt] _.... nut nut ...... peanut ['pi:nAt]

['durd;) ] d;) d;) ['perd;) ]

['du:n'dAnt] dAnt t;) ['pem't;)]

['dordi:dAt] dAt de ['perde:]

['durdAt[] dAt[ pAmp ['pe:m'pAmp]

['durdAts] dAts pAp ['pirpAp]

['dornAt] nAt nAt ['pirnAt]

Other examples of Emma's errors, evidently dueto a variety of gestural processes, includingharmony and the slow release of alveolar closures,include: ['du:'dgtfiz], ['do:llA'tffiz], doughnut please,and ['sslze'tfiz], ['sepg'piz], seltzer please. Sinceisolated forms for both seltzer and please occurredin Emma's repertoire, the last example nicelyillustrates a child organizing her articulationsover a phrase of several syllables (cf. the"coalesced word patterns" ofMacken, 1979).

Variability in imitations. As a final example, letus consider six of Emma's repeated attempts toimitate a word that did not lend itself either togestural harmony or to the labial-alveolar routine:apricot, beprrkat]. (All these examples wererecorded in week 95, except for the third whichwas recorded in week 105.) The word ischallenging because it calls not only for threedifferent locations of gestural closure, irregularlyordered (labial, velar, alveolar), but also for analternating pattern of glottal closure and release.

Table 4 lists Emma's attempts. With severalexceptions she captures certain properties of theword quite accurately: the number of syllables (2­6), the stress pattern (1,4), an initial vocalicgesture (1-4), the constriction degree of the finalvowel (1,3-6), the rough location of at least two outof three consonantal constrictions (2-6) and,ornitting the initial velar intrusions of 5 and 6, thelabial-lingual sequence of these constrictions.

Gestures, Features and Segments in Earlv Child Speech

Table 4. Imitation: Within-word variability in Emma's attempts at apmot.

99

Adulttarget

Order ofclosedconstrictions in target

Emma'simitations

Order ofclosedconstrictions in imitations

['reprrkat) Labial---VelarmAlveolar I. ('alb;;lwahOl)2. ['gp;;l'gA)3. (';;l'fu'kOl)4, [,hAf;;l'tsOl)5. ['g€tgA'pol)6. ['l);;l'hqpw3''thOl]

Apparent consonantal segments in Emma's responses not found in adult target: [b], [g], [f), [ts), [IJ]

LLmVLmVL-"-AV---V-··LV·_·LmA

Yet every attempt contains at least one apparentsegment not present in the model: [b], [g], [fJ, [s]or [I)]. With the exception of [f1 (an error in theexact location and degree of the word's labialconstriction), all these errors arise from a failureof gestural timing or coordination: for [b], [g] and[I)], a failure to open the glottis during oralclosure; for the affricate [ts] (in 4), a relativelyslow release of [t], as in the examples above. Otherindications that Emma had difficulty in managingthe alternating pattern of glottal action in theword come from the brief periods of aspiration(superscript [h)) inserted in 1, 4 and 6. Finally, thewhispered initial vowel of 2 presumably reflects adelay in glottal closure, while the initial velarnasal of 6 reflects a delay in velic closure, as thechild moves from silent breathing to speech. Thus,the principal source of error (apart from errors inthe location and degree of vocalic constrictions)was gestural phasing. No doubt we couldconstruct a set of "rules" relating the observedsegments to the supposed underlying forms of thetarget utterance. But the task would be laborious,and completely ad hoc. A gestural account, bycontrast, is simple and readily intelligible.

GENERAL DISCUSSION

The relation of gestures to features andsegments

We have tried to show how a child's errors inearly words can arise from paradigmaticconfusions among similar gestures in a child'srepertoire and from syntagmatic difficulties incoordinating the gestures that form a particularword. Yet a reader accustomed to think in termsof features and segments may see little differencebetween our approach and those of previousresearchers. For example, Waterson (1971:181)proposes that "...a child perceives only certain ofthe features of the adult utterances andreproduces only those that he is able to cope with";

Macken (1979:29) writes of a child's "... tendencyto combine features from different segments of theadult word"; Ferguson and Farwell (1975:426),commenting on a child's diverse forms for a singleword, suggest that she "... seems to be trying tosort out the features of nasality, bilabial closure,alveolar closure and voicelessness."

What is missing in all these formulations is anexplicit statement of how a percept is linked to itsarticulation. Their implicit conception of the linkseems to be close to that of K. N. Stevens whoanswered a conference question on this matter asfollows: "1 would say that the lexicon isrepresented in abstract units that are neitherdirectly articulatory nor directly acoustic, Arelation projects these abstract units both to theacoustics and to the articulation. As you can see, Iam taking the view of Jakobson, originallypostulating something like features which haveboth acoustic correlates and articulatorycorrelates and must have both" (Mattingly &Studdert·Kennedy, 1991, p.194).

We have already stated the key objection to thisposition: a feature is a property, not an entity.Phonetic features are not like facial features­eyes, nose, mouth-each of which can, at least inprinciple, be removed from one face andtransferred to another. Rather, phonetic featuresare like the size and shape of a nose: we cannotremove either without removing the nose in whichthey are embodied. In short, features areattributes, not substantive components.

Of what substantive object or event, then, is thefeature an attribute? The customary answer, thephonetic segment or phoneme, will not do, becausesegments are defined by their features: the answeris circular as long as we have no independent (andno substantive) definition of a segment. Wepropose, instead, that a feature is an attribute of agesture. We assume that gestures, like Jakobson'sfeatures, "...have both acoustic correlates andarticulatory correlates and must have both."

100 Studdert-Kenned1/ and Goodell

Because these two sets of correlates arenecessarily isomorphic, the gesture is the linkbetween a speech percept and its articulation. Inthis respect, speech gestures resemble every otherimitable act: their perceptual representationspecifies their motor form.

Adopting the gesture as a vehicle for the featurealso permits an independent and substantivedefinition of the segment. We noted earlier thatthe canonical syllable was the first step towarddifferentiation of two major classes of oral gesture:vocalic and consonantal. Let us now note, further,that although consonant and vowel gestures mayinteract (as in Emma's preferences for particularconsonant-vowel combinations) they are notinterchangeable: we do not find a child (or anadult) making the mistake of replacing a nar­row/mid/wide vocalic gesture with a closed/criticalconsonantal gesture, or vice versa. No doubt sucherrors are blocked by the biophysical structure ofthe syllable, that is, by its alternating pattern ofopening and closing the mouth. In any event, weview differentiation of the syllable into its closedand open phases as a move toward the formationof gestural routines with a narrower domain thanthe word, namely, the encapsulated patterns ofprecisely phased laryngeal, velic and oral gesturethat we term segments (cf. Menn, 1986; Studdert­Kennedy, 1987).

The emergence of segmentsThe emergence of segments as elements of word

formation in a child's lexicon seems, then, to havetwo aspects. First, is the grouping of all instancesof a particular sound-gesture pattern into a singleclass, presumably on the basis of theirperceptuomotor, or phonetic, similarity (e.g.,grouping the initial or final patterns of dad, dog,bed, etc. into the class /d/). Second is thedistributional analysis and grouping of thesegesture-sound patterns into higher order classes(consonants, vowels) on the basis of their syllabicfunctions (onset, nucleus, coda).

Two possible selection pressures may precipitateformation of these categories. One pressure istoward economy of storage. As the lexiconincreases, words may organize themselvesaccording to their shared gestural and soundproperties. Recurrent patterns of laryngeal andsupralaryngeal gesture would thus formthemselves into classes of potential utility forrecognition or activation of lexical· items(Lindblom, 1989; Lindblom, MacNeilage, &Studdert-Kennedy, 1983).

A second pressure may be toward rapid lexicalaccess in the formation of multiword utterances.

Several authors (e.g. Branigan, 1979; Donahue,1986) have reported evidence that the form ofearly multiword combinations may be limited bythe child's ability to organize the requiredarticulatory sequences. Donahue, for example,reports her son's "adamant refusal" to attempt twosuccessive words with different initial places ofarticulation. Such findings imply that theintegration of gestures into independent phonemiccontrol structures, or articulatory routines (Menn,1983), may serve to insulate them fromarticulatory competition with incompatiblegestures, and so facilitate their rapid, successiveactivation in multiword utterances.

SUMMARYWe have presented three lines of evidence for a

gestural model of phonological development thatcan deal coherently with (i) the continuous transi­tion from babbling to speech, and (ii) the word asthe contrastive unit of early phonology. For thetransition from babbling to speech, details of thedevelopmental course may vary from child tochild: not every child displays gestural harmony,not every child who does so escapes from harmonyinto the lexicon by a non-harmonious gesturalroutine. Nonetheless, every child does have to finda path from babbling to speech. We have arguedfrom one child's path that the gesture, with itsroots in the child's prelinguistic mouthings andvocalizations, is a more valid unit of linguisticfunction than the feature with its roots in theformalisms of adult phonology.

With regard to the word as the contrastive unitof early phonology, we have reviewed two lines ofevidence that the gesture, rather than the feature,is the basic unit of a word's articulatory organiza­tion. First, the same syllable may take differentforms as a function of the target word, or phoneticcontext, in which it appears. A featural accountwould not predict this outcome, because a givensegment carries the same featural predicates re­gardless of context; a gestural account, on theother hand, with its emphasis on the syntagmaticprocesses of articulatory action, finds the outcomenatural. Second, in our subject's attempts to artic­ulate a word with a pattern of alternating glottalgestures and a varied sequence of oral constric­tions, the attempts were so diverse, so variablefrom occasion to occasion, that a featural accountof her utterances would be little more than a listof arbitrary deletions, additions, and substitu­tions. By contrast, the present approach attribut­ing the child's errors to imprecise execution andtiming of the gestures that form the target word,offers a simple and perspicuous account.

Gestures, Features and Segments in Earlv Child Speech 101

Finally, we have argued that the feature can beruled out as a basic unit of eith€Jr speechperception or speech production on rationalgrounds, because it is, by definition, an attributethat has no existence independently of the obj€Jctor event that it describes. We reject the segmentas the primary vehicle of the feature because asegment is (circularly) defined by its features. Wepropose instead that a feature be viewed as anattribute of a gesture, and that segments bedefined, superordinate to the gesture, as emergentstructures, comprising recurrent, spatiotemporallycoordinated, gestural routines.

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FOOTNOTES'In B. de Gelder & J. Morais (Eds.), Language and literacy:

Comparative approaches. Cambridge, MA: MIT Press (in press).I Fant (1962, p. 4) remarked many years ago concerning the theoryof Jakobson, Fant and Halle (1952/1963): " ... its formulations aremade for the benefit of linguistic theory rather than forengineering or phonetic applications. Statements of the acousticcorrelates to distinctive features have been condensed to anextent where they retain merely a generalized abstractioninsufficient as a basis for practical applications:' The same is trueof subsequent attempts to formulate acoustic and articulatorycorrelates of the features.

2In what follows we use the term "gesture" to refer either to anunderlying abstract control structure, or to a concrete instance ofa gesture activated by this structure, relying on context to makeclear which is intended.

3These categorical values, axiomatic within gestural phonology,may have emerged evolutionarily, and may still emergeontogenetically, through auditory and articulatory constraints onindividual gestures (Stevens, 1989), and on the entire set ofgestures within the child's developing lexicon (Lindblom, 1986;Lindblom et aI., 1983).

4The problem and criteria for its solution are thoroughlydiscussed by Vihman and McCune (in press).

5Much of the controversy over the issue of continuity betweenbabble and speech has arisen, in our view, from a misreading ofJakobson's claims, and from a failure to diStinguish betweenphonetic form and phonetic function. Jakobson himself drew thisdistinction quite clearly. Although he believed that" ...a shortperiod may sometimes intervene ... in which children arecompletely mute," he also recognized that: "For the mostpart.. .one stage merges unobtrusively into the other, so that theacquisition of vocabulary and the disappearance of theprelanguage inventory occur concurrently" (Jakobson,1941/1968, p.29). In fact, he assumed what later studies haveconclusively demonstrated (e.g., MacNeilage, Hutchinson, &Lasater, 1981; Oller, Wieman, Doyle, & Ross, 1976; Vihman,Macken, Miller, Simmons, & Miller, 1985) that listeners oftencannot distinguish, by phonetic form alone, a "child's embryo­words from the pre-language residue" (Jakobson, 1941/1968,p. 29). The discontinuity that Jakobson (correctly) posited was adiscontinuity of function, not of form.

6We thank Susan Brady for pointing this out to us.