Recent developments in speech to children: We've come a long way, baby-talk

Language Sciences, Volume Printed in Great Britain

10, Number

I. pp. 89-l IO. 1988. 0

03884001/88 163.00+ .oO 1988 Pergamon Press plc

Recent Developments in Speech to Children: We’ve Come a Long Way, Baby-talk

John Neil Bohannon III

Amye Warren Leubecker

Butler University

University of Tennessee at Chattanooga

ABSTRACT Children do not acquire language in a void; their hypothesized language learning devices typically operate within conversations with more mature language users. These sources provide children with the primary linguistic data for incorporation in their own speech. Despite the fact that many studies have reported the features which distinguish speech to children (child directed speech or CDS), from speech between adults, the study of why CDS is so prevalent across languages seems to have been largely neglected. However, in this paper we offer a model that allows children to control the complexity of the speech they hear within conversations on a moment-to-moment basis. Experimental and observational data are presented that clearly delineate the reciprocal nature of how speakers “fine-tune” their speech to listeners. Regardless of the mechanism that results in a simplified CDS register, a second and more important question pertaining to the role of CDS in language acquisition remains. Recent reports on longitudinal predictions of language gains from early maternal CDS measures are reviewed. The studies are analyzed separately for the adequacy of their conceptual and statistical constructs. Most of the negative findings may be attributed and inappropriate matching of conceptual relations with simple linear regression models. A new model incorporating the reciprocal, non-linear relations is proposed for a possible test of the effects of CDS on language development. Lastly, new data on the possible existence of negative evidence is reviewed. Adults clearly react differentially to children’s well- and ill-formed utterances within conversations. The ramifications of both CDS and the existence of negative evidence for learnability theory are discussed.

INTRODUCTION

In many current approaches to the language learning problem, the speech that children hear determines only the particulars of their native langauge (e.g. permissible sounds and lexical items), but cannot account for the whole of language acquisition, especially syntactic development (e.g. grammatical categories and government binding; Pinker 1979; Chomsky 1980; Wexler and

90

Language Sciences, Volume 10, Number 1 (1988)

Cullicover 1980). Rather, children are thought to be pint-sized cryptographers industriously using certain innate biases to crack important grammatical codes embedded in the language corpus. These biases or “constraints on learning” are considered necessary because the child’s language environment is postulated to be too degenerate and impoverished to account for the acquisition of rich grammatical relations. At one time, the term “degenerate” was thought to mean “too complex” and that children’s basic language data were riddled with grammatical errors (Chomsky 1965). In fact, Bever et al. (1965) once wrote, “There is little evidence that adults engage in careful limitation of their linguistic output when conversing with children.” (p.470.) Today, the term degenerate is still applied to children’s language environments, but in a very different way; the language adults use with children is now thought to be too simple or limited in the varieties of grammatical structures it demonstrates. Moreover, the language environment presumably does not support language learning because adults do not correct or provide feedback (negative evidence) on their children’s grammatical mistakes. Although what is meant by a “degenerate” language sample has changed over the years, the argument that what children hear cannot account for their developing language has remained unchanged, though not unchallenged (e.g. Wexler and Cullicover, 1980; Hoff-Ginsberg and Shatz 1982). Despite the recognition that children the world over are presented with a special language register (Warren-Leubecker and Bohannon 1985), possible causal relations between language development and the language environment have been prematurely rejected (e.g. Gleitman and Wanner 1984). Over the past 15 years, a great deal of attention has been focused on the special nature of the child’s language environment and social interaction as possible explanatory factors in the language acquisition process (Bruner 1978; Bohannon and Warren-Leubecker 1985). Although few doubt that human children are biologically predisposed to speak and understand language, it is clear that mere exposure to the soundstream of speech (e.g. from television) is insufficient for normal language acquisition (Sachs and Johnson 1972). Deaf children isolated from any coherent spoken or sign language input also do not develop extensive structure in their own spontaneous signed communications (Goldin-Meadow and Feldman, 1977; Goldin-Meadow 1982; Whitehurst 1982). Exposure to the linguistic environment must be supplemented by a social system which allows the child to interact with a structured language corpus (Moerk 1975, 1983). However, the particular features of the language environment and social interaction system which are necessary for, or even facilitate normal language development are as yet largely undetermined (see Gleitman et al. 1984; Tomasello 1988, for some positive effects). On closer inspection of the language learning environment, investigators

Recent Developments in Speech to Children

91

discovered that the language input to the child was not so variable and disorganized as had once been supposed. We now know that adults almost from the moment of the child’s birth, modify their speech in very consistent ways when addressing children (Snow and Ferguson 1977; Fernald 1984). This special subset of language behaviours has been called motherese because it typifies mothers’ speech to children (Newport et al. 1977) baby talk because it often contains phonological simplifications (Ferguson 1977) or more broadly, just child directed speech (CDS) since they are the most frequent recipients of this language register (Warren-Leubecker and Bohannon 1984). By whatever name, (and we will use CDS henceforth), this special speech register is characterized by short, simple, grammatically correct and highly repetitive sentences composed of concrete words that usually describe something in the immediate environment (Snow 1972, 1977, 1979, 1981). CDS is also composed of more questions, declarative sentences, and attention-getting devices than adult directed speech. The prosodic features of CDS include a higher and more variable fundamental frequency, more variable intensity, a slower rate of speech, and significantly longer pauses between the major syntactic constituents. Many of these features, such as short, simple sentences (measured in mean length of utterance or MLU) and turning the content of conversation to the child’s immediate environment, are consistent over the 14 languages studied to date (for reviews see Snow and Ferguson 1977; DePaulo and Bonvillian 1978; Gleason and Weintraub 1978; Nelson et al. 1983). Furthermore, several studies have found that children prefer to listen to speech containing features of CDS rather than the speech more typical of adult conversations (Friedlander 1968; Rileigh 1973; deCasper 1980; Fernald 1984). The prevalence of these features in CDS contradicted the early descriptions of “degenerate” language samples presented to children as their primary language data (Chomsky 1957, 1965). Thus, researchers (e.g. Moerk 1975, 1983) began to argue that CDS and the special characteristics which distinguish it from adult-adult speech appeared to be specially designed to teach language to children, and began to rely on CDS in an effort to rescue language acquisition explanations from the grasp of the strong nativistic theories (e.g. Chomsky 1965). The fact that the language problems presented to language learners were much simpler than originally surmised persuaded many researchers that most of the knottier problems concerning language acquisition might soon and easily reveal their secrets (Wexler and Cullicover 1980). Unfortunately, simple answers have not been forthcoming due to the confusion concerning the appropriate tests of the “true” relation between features of CDS and language development in children. The investigation of this relation has been diverted and obscured by some irrelevant issues and inappropriate methods. The confusion over the role

92

Language Sciences, Voiume10, Number I (1988)

of CDS has now grown to encompass the possibility that simplifying speech to children actually hinders children from more rapid rates of development (Wexler and Cullicover 1980). The current contribution will focus on the issues related to the regulation of CDS in speech and to the tests of its possible effects on those acquiring language. In addition, because the child’s language environment is not made up of disembodied sentences, but conversations in which a child’s utterances are typically preceded and followed by adult speech, we will also review the evidence on adults’ reactions to children’s language errors. WHY DOES CDS OCCUR? THE “FINE-TUNING”

HYPOTHESIS

The first wave of reports concerning CDS focused on the specific situations in which the features of CDS occurred. CDS has been observed in diverse contexts ranging from mothers’ and fathers’ speech to their own and other children (Snow 1972; GolinkofT and Ames 1979; Warren-Leubecker and Bohannon 1984) to any adults’ speech to children (Snow 1972) to children’s speech to other children (Shatz and Gelman 1973; Gleason and Weintraub 1978) to speech to foreigners (Ferguson 1975; Warren-Leubecker and Bohannon 1982), adult retardates (Pratt et al. 1976), the elderly (Culbertson and Caporael 1983), dolls (Sachs and Devin 1976; Warren-Leubecker and Bohannon 1983), pictures of children (Bohannon et d. 1982), and dogs (Hirsh-Pasek and Treiman 1982). Why features of CDS should emerge in all these contexts is curious. Some argue that features of CDS have nothing to do with the desire to teach language or even to be understood, but with the need to gain a potential listener’s attention, to express affection, or to demonstrate the speaker’s social superiority (e.g. Brown 1977; dePaulo and Coleman in press). An alternative explanation is that speakers will “fine tune” the length and compIexity of their speech to the perceived or actual comprehension capacities of the listener. Gleitman and Wanner (1984) argued that if speakers “fine-tune” their speech to children, then evidence is required for three factors: (1) a method to determine the optimum simplicity of one’s speech, (2) a method to determine the sophistication of the listener being addressed, and (3) the “machinery” for the rapid implementation of factors (I) and (2) in ongoing conversation. The one-tuning system appears to function in the following manner. Adults tend to use short and simple sentences (CDS) with chifdren, and the length and complexity of those sentences tends to increase as the children grow more linguistically mature (Snow 1972). The most likely influence on this pattern is a feedback system that operates within normal conversation, and depends upon cues from the listener (Gleason 1977). Children who are linguistically immature (as well as foreigners) tend to understand short and simpler sentences, and signal their comprehension success to speakers using such sentences. Longer

Recent Developments in Speech to children

93

(and probably more conceptually and grammatically complex) sentences tend to result in comprehension difficulty for these children, and these comprehension difficulties are also communicated to their conversational partners. Thus, the ability to fine-tune one’s speech would be aided by feedback from the listener indicative of the success or failure of the prior communication. Many studies (Bohannon and Marquis 1977; Gallagher 1977; Wilcox and Webster 1980; Bohannon et al. 1982; Lederberg 1982; Warren-Leubecker and Bohannon 1982, 1983; Stine and Bohannon 1983; Bohannon in press) have shown that grammatical complexity and MLU are controlled on a moment- to-moment basis by feedback indicative of the listener’s ability to understand. According to Garvey (1977) children are less likely to answer questions and requests appropriately, and more likely fail to carry out commands and to respond with “What?” or “Huh?” (i.e. contingent queries) when the sentences carrying these functions are relatively long and complex. Cross (1977, 1978) found that when children of different ages are matched on their ability to comprehend language, there are no differences in the syntax of the maternal speech addressed to those children. The feedback effect is so pervasive that even three and four year olds will simplify their speech following a sign of non-comprehension from another child or a “talking” doll (Shatz and Gelman 1974; Warren-Leubecker and Bohannon 1983). Gleason (1977) observed that whereas adults mark successful communication by nods and statements such as “yeah”, “O.K.“, or “sure”, young children rarely offer such feedback. A lack of feedback indicative of comprehension could produce problems for the fine-tuning hypothesis. However, it may be that the lack of these expected signals is taken to be a sign of noncomprehension by adults, resulting in the adults’ attempts to clarify using features of CDS. Other researchers have found that when feedback cues are unavailable as in the case of talking to dolls (Sachs and Devin 1976) and talking to pictures of children (Bohannon et al. 1982), speakers rely on their sterotypic conception of what their listeners might comprehend. There are studies (Gleason and Weintraub 1978; Warren-Leubecker and Bohannon 1982) suggesting that speakers respond to their expectations about their listeners rather than responding on the basis of the listeners’ actual knowledge. Such speech adjustments to the perceived or expected comprehension capacities of listeners may account for the finding that some features of CDS are commonly used to address dogs (i.e. doggerel, Hirsh-Pasek and Treiman 1982). Finally, Stine and Bohannon (1983) found that a noncomprehension cue from a child tends to depress the MLUs of several of the adult utterances that follow the cue. Thus, few such cues may be required to maintain the level of short and simple utterances required by the child. LSC

1011-G

94

Language Sciences, Volume 10, Number 1 (1988)

Overt

signals

children’s

of comprehension

true or absolute

words, children for a variety

ability

may indicate

of transitory

are probably

to understand

only

roughly

their mother’s

indicative

speech.

either success or failure with a particular

reasons

that are unrelated

to syntactic

of

In other utterance

complexity

and

sentence length. Children may simply fail to attend to the entire utterance, or they may be ignorant about the meaning of a single word out of a multi-word string. Even less accurate indicators of comprehension are mere age or productive language abilities. For example, prior to the utterance of the child’s first words come gaze and attentional cues that severely depress the complexity of maternal

speech

(Fernald

1984).

During

the

child’s

holophrastic

stage,

maternal utterance length continues to grow, leading some (Hoff-Ginsberg and Shatz 1982) to conclude that mothers are not “fine-tuning”. It is also likely that parental expectation of their infants’ linguistic ignorance in congress with few comprehension cues of any sort leads to relatively complex speech addressed to infants aged O-13 months. Once these children begin to show rudimentary signs of comprehension, mothers begin to reduce the length, complexity, and variety of grammatical forms in their speech. Thus, older children be provided with simpler speech than infants. In some

may at times actually studies, one point of

measurement may occur prior to the infant’s primitive comprehension cues and the other occurs after such cues begin to appear. The resultant decrease in maternal MLU with their child’s increasing age has led some researchers to inaccurately reject the “fine-tuning” hypothesis. Although there are other possible indicators of comprehension, verbal responses such as “What” or “Huh?“, failures to comply with requests, puzzled expressions, and total lack of responsiveness are the most likely moment-to-moment indices of transient states of comprehension that are available to mothers. Thus, while the comprehension feedback

explanation

is not the only account

extant

for the occurrence

of CDS,

it does not explain much of the observed data (for a review see, DePaulo and Coleman in press). In summary, CDS is the linguistic product of those communicative interchanges in which more adept speakers of a language attempt to communicate with less adept language users. Effective communication demands that the one with the superior language skills adapt this speech to the abilities of the listener (for concurring explanations see, Hoff-Ginsberg and Shatz 1982). The resulting effect is that most speakers’ utterances will be consistent and lack variability between speakers when addressing the same child. Notice that this places an added burden on the immature language learner. The child is the source of the controlling signals that tailor the child’s linguistic environment. Hence, ineffective or misleading cues could cause excessive variability in the complexity of the utterances addressed to the child which may in turn affect

Recent Developments in Speech to Chihkn

95

exposure to the linguistic environment which encourages language development. Clearly, children differentially signal communicative success depending upon the length and complexity of utterances addressed to them (Geitman and Wanner’s factor (Z), above). Communicative failure results in the simpli~cation of following utterances (factor (l), and both of these occur on a momentto-moment basis within conversation (factor (3). There can be little doubt that the normal demands of communication effects a simple mechanism whose primary product is the simplified CDS register. Moveover, this mechanism is independent of an adult’s intentions in the communicative interchange. Whether or not adults are consciously trying to “teach” language is irrelevant to the system, as long as there is a minimum interest in the passage of information between the conversational partners.

CDS EFFECTS IN LANGUAGE DEVELOPMENT: CONTRADICTORY EVIDENCE

Whatever the reason for the occurrence of CDS, it is another matter altogether to determine whether CDS has any beneficial effect upon the language development of the children who hear it. Although it appears to be well-suited for aiding the ongoing moment-to-moment comprehension of the listening child, does it aid language development? There are actually several ways in which CDS could affect language acquisition (either the mere occurrence of certain CDS features or the frequency of occurrence of certain features may be important, and these features may enhance or retard language growth) and several areas of child language development that may be affected (phonological, semantic, syntactic and pra~atic). However, no one piece of evidence from one domain should be taken to imply the same relations or lack thereof in any other domain. Perhaps CDS should affect syntactic development but play little role in phonological growth, or vice versa. In fact, there is ample evidence to suggest that CDS is functionally related to the child’s conceptual and vocabulary development (for review see Hoff-Ginsberg and Shatz 1982; Bohannon and Hirsh-Pasek 1984), but contradictory evidence has emerged in the area of CDS effects on syntactic development. Therefore, we will focus the remainder of this discussion on the effects of input on the child’s grammatical structure or syntax. Only in the domain of syntactic development have the effects of CDS as opposed to more general language input been examined (Newport et al. 1977; Furrow et al. 1979; Gleitman et al. 1984). However, despite repeated investigations and pronouncements to the contrary, the question of whether CDS has any effect on the child’s syntactic acquisition has not yet been satisfactorily

96

Language Sciences, Volme 10, Number 1 (1988)

answered. Provided that there are adequate dependent measures available, we could test the hypothesis that more “CDS” yields more rapid development in syntax than less “CDS”. We could also identify those aspects of the child’s language development that emerge independently of CDS or a simplified linguistic environment. In general, the model for assessing the effects of CDS involves assessing maternal speech and child speech in conversation at an initial interview (time 1 or Tl) and a subsequent assessment of the child’s language at another interview (time 2 or T2). Figure 1 displays the intuitive direction of the

Cs*+r

-

cs

c -

T2

Tl

Time of testing

Figure 1.

*Maternal speech addressed hension. ***Child’s speech.

to

child.

““Childs

compre-

CDS effect (arrow b) from the mother’s speech at Tl to the child’s speech at T2. As stated before, the maternal speech (MS) is at least partially controlled by clues to the child’s comprehension (Cc) and such is noted as arrow a. The changes in productive speech which accrue from differential comprehension of CDS is noted as Cs below. The first comprehensive study on the relationship between CDS and syntax acquisition comes from Newport et al. (1977). They studied 15 mother-child dyads to determine whether individual differences in the mother’s speech predicted the child’s language growth. The children ranged in age from 12 to 27 months at Tl with MLUs ranging from 1 to 3.65. Maternal utterances collected during the first of two interview sessions (MS at Tl above) were analyzed along a number of syntactic dimensions including well-formedness, sentence length, structural and psychological complexity and sentence type, among others. The children’s utterances were collected during two interview sessions six months apart (Cs at Tl and T2 above) and were coded for syntactic complexity (estimated through MLU), mean noun-phrase frequency and length, mean verbphrase frequency and length, inflection of noun-phrases (plural marking)

Recent Developments in Speech to Children

97

and auxiliary (modals and tense marking) (see Newport et al. 1977 for further discussion). As Newport et al. (1977) point out, one must go beyond simple correlations to assess the impact of maternal speech on language growth. Simple correlations could reflect, “The adjustment of the mothers to their child’s age and initial linguistic level . . .” (p. 10.) This effect is symbolized by arrow a in Figure 1. These authors argued further that, “the amount of the child’s improvement over a given time span depends on his age and baseline at the beginning of the interval (this must be so since the language acquisition curves are not linear).” (p. 10.) In order to avoid these potential problems, they employed the following procedures: (1) they obtained a language growth function for each child by computing productive (Cs) language differences between Tl and T2 (arrow c) and child’s speech at T2 that was due either to the child’s age or his level of language achievement at Tl. By statistically equating subjects for age and base level through partial correlations, they hoped to assess the residual relationship between CDS and language acquisition. In summarizing the results of this analysis, the authors wrote, “The measures of child language that we take to be indices of universal aspects of language and structure (e.g. number of noun phrases and verb phrases per utterance) are, so far as we can see in this limited study, insensitive to individual differences in maternal speech styles.” (Newport et al. 1977, p. 27). In contrast, CDS does contribute to the child’s language in what are called language specific, paradigmatic devices (e.g. tense and plural markings that are specific to the language being learned). By way of example, the mother’s use of yes/no questions contributed positively to the child’s use of the verbal auxiliary. In sum, the Newport et al. (1977) study offers no evidence of an effect of CDS on the general properties of syntactic learning. However, Furrow et al. (1979) have challenged their conclusions, from both conceptual and statistical standpoints. They proposed that CDS has qualitatively different effects on the child at different ages and linguistic levels, and that the potential effects of CDS are not equal over time. Thus CDS could have functional impact on the child at age A, (linguistic level A), but primarily a content effect at age C (linguistic level C). Under this kind of a model, the potential syntactic influence of CDS on a child’s language acquisition could be obscured by equating language level and age when those levels or ages were not actually equal. A child at age 2 years, language sophistication level B, for example, may demonstrate an effect that, under Newport’s calculations, would show evidence of “global language learning”. This effect would be washed out if the two year olds’ results were equated with the child of one year (language level A) whose results demonstrate no susceptibility to the syntactic form of CDS.

98

Language Sciences, Volume 10, Number 1 (1988)

Furrow et a/. (1979) attempted to control for this confounding by studying a homogenous sample of seven, one-word speakers who were all 18 months old at the first interview

(Tl)

and 27 months

at T2. Additionally,

all the children

were holophrastic and equated for language comprehension at Tl. The speech samples from the mothers and the children at Tl and T2 were analyzed along a number of syntactic and semantic dimensions. Maternal speech was coded for variables of (1) sentence type (e.g. declaritives, imperatives), (e.g. words, sentence nodes, verbs-main, auxiliary), and

(2) structural units also as units, (3)

representatives of Brown’s grammatical morphemes (e.g. tense, plural), and (4) MLU. Child speech was coded for mean length of utterance, verbs per utterance, noun phrase per utterance, auxiliaries per verb phrase and inflections per noun phrase. Correlations between maternal variables and child language growth were assessed at both Tl and T2. The character of the maternal speech over that period did not alter significantly. reported significant negative correlations

The results of this study were the first between measures of maternal speech

complexity and gains in children’s productive speech over time. Following the publication of Furrow et al. (1979), a further series of studies addressed the CDS-acquisition question. Gleitman et al. (1984) published a reanalysis of a subset of their data. The new study selected six of the youngest children who were nearly all holophrastic at Tl. Again, the authors statistically partialled out initial variability of the children’s productive speech from both the maternal Tl and the children’s productive speech at T2. The resultant correlation matrix of more than 80 Pearson r’s revealed only four significant relations. Moreover, of the few significant correlations found, only one or two reportedly made sense theoretically to the authors. For example, the amount of unintelligible maternal utterances was significantly correlated with certain syntactic gains. Despite the certainty that two or three of the correlations were spurious, GNG again pronounced that they had adequately assessed the true relation between CDS and syntactic development, and that it was virtually non-existent. There are several possible reasons why the three studies differ so greatly. For example, even if Gleitman et al. (1984) had followed the basic assumptions of their statistical tests, the results may have been due to the different developmental lags between times of measurements used in the Furrow and their own studies (six vs nine months). That is, the casual lag between MS at T1 and children’s productive speech (Cs) at T2 may be nine months and any assessment prior to that time may not show significant relations. In contrast, other variables may have occurred in the longer lag of the Furrow study that may moderate the real relation between MS and Cs discovered by them. A recent study (Hoff-Ginsberg 1985, 1986) tried to account for the possibility of

Recent Developments

in Speech to Children

99

different casual lags. This study used 22 pairs of mothers and two-year-olds (2.0-2.6) and assessed them in home interviews every two months for six months. All the children had initial MLUs over three words, and the variability of children’s Tl productive speech was again partialled out of all maternal (MS) measures and subsequent assessments of language growth in the children. Despite the sensitivity to the casual lag question, the author ignored the strong possibility of spurious correlations, and thus tried to explain the 10 significant correlations out of the 400 or so calculated. Clearly, the field of language acquisition research must suspect reports that do not follow the basic assumptions of the statistics employed in this study. Both Gleitman et al. (1984) and Hoff-Ginsberg (1985, 1986) essentially found no reliable relation among their variables. It now remains to be explained why none of their tests revealed relations stronger than mere chance. We could fail to reject the null hypothesis, and conclude that no relations were found because no relations exist. On the other hand, inadequate statistical tests neither prove nor disprove any hypothesis. Despite the muddiness of the current positions and reports on the effects of CDS on language development, some methodological differences in the aforementioned studies lend hope for an eventual resolution of the contradictions. Newport et al. (1977), Gleitman et al. (1984) and Hoff-Ginsberg (1985, 1986), using children of varying ages, found that maternal MLU was unrelated to MLU gains in their children. All these studies (including Furrow et al. 1979) assumed a simple linear relationship between maternal MLU and children’s gain scores. Their hypothesis was that the shorter and simpler the maternal speech (regardless of the child’s age and productive MLU), the greater the child’s gains should be. The linear model predicts, in a preposterous assertion f?r older children, that the greatest gains in children with MLUs greater than four words should be found when their mothers exclusively use holophrases! In these, more sophisticated children, the maternal MLU vs child gains relationship is most likely curvilinear, with some optimal middle level of length and complexity yielding the greatest gains (see George and Tomasello 1984, for experimental support of curvilinear functions in comprehension). The only time a simple, negatively sloped linear relationship should hold is with holophrastic children. Only then should single word utterances be related to the largest gains. This occurred in the Furrow study of seven holophrastic children. Significant negative correlations were found between their subject’s MLU gains and maternal MLU. Another significant problem was that the Newport et al. (1977), Gleitman et al. (1984) and Hoff-Ginsberg (1985, 1986) studies assumed that assessing the children’s productive speech at Tl was sufficient to predict the variable use of

100

Language Sciences, Volume 10, Number 1 (1988)

CDS in the mothers. in their partialling directly

assessed

In other words, procedures,

all previous

with the exception

the child’s comprehension

studies

used this assumption

of Furrow

level. To the extent

et al. (1979) who that productive

speech lags behind receptive speech and inaccurately specifies optimum differences, the residual correlation calculations will err proportionately

CDS (see

Figure 1). The more complete model suggests a dynamic and reciprocal relationship between the developing children’s language ability and the children’s language environment supplied by their mothers (and other adults). This hypothesis involves differentially time (see Bohannon

curvilinear regression functions relating MS and Cs over and Hirsh-Pasek 1984, for a step-wise regression solution,

James and Singh 1978, for a least-squares solution, or James and Tetrick 1986, for a structural equation solution). A recent study (Barnes et al. 1983) of 32 children found evidence of such a reciprocal relationship between children’s language gains over two years and maternal speech (for a more complete discussion see Bates c’t al. 1982; Bohannon and Hirsh-Pasek 1984). In summary, the present report proposes a different model of maternalchild verbal interaction that may account for prior discrepancies. Divergent results in the syntactic domain may be due to psychology’s reliance on linear statistical models even in cases where such models are unwarranted. The Pearson correlation, albeit with an age-partialled modification, relies upon an assumption of linear relationship between the variables. Yet, maternal speech and child language development most plausible model relating

are both admittedly the mother’s verbal

nonlinear behaviour

functions. The to the child’s

emerging linguistic skills is both nonlinear and reciprocal. Given these propositions, it only remains to test the new model utilizing any of the newer statistical techniques, step-wise regression, reciprocal least-squares, or structural equations

(LISREL).

THE ISSUE OF NEGATIVE Recent

theoretical

EVIDENCE

arguments

from

the

language

learnability

literature

concur with the Newport et al. (1977) Gleitman et al. (1984) and Hoff-Ginsburg (1985, 1986) results. Learnability theorists (Pinker 1979, 1987; Wexler and Cullicover 1980; Wexler 1982) suggest that exclusive exposure to CDS would not only be ineffective in teaching general syntactic properties, but would be detrimental to the task of language learning. In fact, learnability theories focus more on what mothers are not saying rather than the characteristics that are present in CDS. In particular, it is argued that (1) mothers do not supply enough examples of the wide variety of grammatical structures available in the

Recent Developments in Speech to Children

101

mature adult form of the language, and (2) that mothers do not provide corrections when their children make grammatical mistakes. Thus, children might falsely conclude that they had induced the grammar, hearing no more complex counter examples or corrections from the input. In fact, these authors argue, CDS does not provide enough language information to either correct hypotheses, to narrow down hypotheses about the candidate grammars or to permit generation of the more complex constructs in the grammar. In short, how could the child, exposed only to CDS, learn to speak the complex language evidenced in his speech by 4 years of age? These theoretical concerns ally with the reports of some of the aforementioned studies and go beyond these findings to suggest that CDS is not an appropriate explanation for the syntactic aspects of language acquisition. Many of the assumptions of learnability theory remain untested, so at this time the claim that CDS is an ineffective language teaching device crucially rests on empirical resolution of the above studies. One of the easily testable assertions of learnability theory involves the assumed lack of counter examples or corrections provided to language learning children. Within the new learnability approaches, the task of avoiding and correcting errors is assigned to the structure of language itself. That is, simple exposure to correct sentences restricts the possible set of language rules that children may select. Indeed, the computer-like learning mechanisms that are now being proposed by some learnability theorists are so powerful that new innate constraints are necessary to explain the relatively slow rate of syntax growth in children (Wexler 1982)! Regardless of the theoretical muddle surrounding the exact mechanisms involved in acquiring language (HoffGinsberg and Shatz 1982) the possibility that adults might react differentially to children’s well or ill-formed utterances has become a central issue to the nativistic explanations of language development (see Pinker 1979). Initial data bearing on this issue of negative evidence was reported by Brown and Hanlon (1970), who found that their three children received no explicit correction (i.e. negative evidence) during an intermediate stage of syntactic development where the children were producing both correct and incorrect forms of the same construction. If children’s conversational partners provide corrective feedback, then most of the powerful learning mechanisms, and most of the innate linguistic constraints recently proposed would become unnecessary. New studies have begun to question the Brown and Hanlon (1970) conclusion. Hirsh-Pasek et al. (1984) found that parents tend to repeat their young child’s language errors significantly more often than the child’s wellformed sentences. Demetras et al. (1986) also observed that parents tend to break their conversational “flow” of information with more questions and repetitions following a syntactic error than following an errorless utterance.

102

Language Sciences, Volume 10, Number 1 (1988)

Recently, responses sources.

another

to children’s One

study

(Bohannon

et al.

well- and ill-formed

set (Bohannon

and

Marquis

1986) closely

speech.

The data

1977) was

examined came

from

adult two

a set of naturalistic

conversations between 14 adults and a single child (aged 2.8) and four months later five more adults with the same child (aged 3.0 years). This set of transcripts allowed the comparison of one child’s differential error rates and adult responses across a variety of listeners and estimates of short-range developmental change. The second data set consisted of transcribed conversations between ten children (aged 1.8-3.1) and both their parents (Warren-Leubecker and Bohannon 1984). These data provided confirmation of some of the basic relations found with the single child, and a broader developmental scope (some of the children were still holophrastic). Both sets of transcripts (about 4000 adult and 3000 child utterances) were coded for language errors in the child. Four types of errors were independently coded, pragmatic, semantic, syntactic and phonological errors. Adult responses to well or ill-formed child utterances were examined in two ways. The first centered on the probability of adult repetition following both well and ill-formed utterances (following Hirsh-Pasek et al. 1984). Although almost any differential response would serve the informational requirements of negative evidence (Demetras et al. 1986), repetition might provide additional information on the correct form of language. Data from the first set of transcripts revealed that adults tended to differentially use repetition after a syntax (well = 18%, ill = 27%) or phonology (well = 13%, ill = 29%) error. Moreover, this effect was modified by the length of the child’s utterance with little differential adult responding (and also fewer child errors) in sentences less than four words in length. In contrast, when the child’s sentences were five or more words in length the rate of adult repetition grew to over 40% while the rate of repetition of well-formed utterances shrank to 10% (p< .Ol). It seemed that adults were both focusing on pronunciation errors, and correcting the child’s productions that were at the edge of the child’s linguistic ability. A second examination of adult responses was conducted on the second data set of mothers and fathers with their children. Here children’s errors were coded for the number of syntax and phonological errors that occurred in each sentence. Moreover, the adult responses were examined for corrections of the exact error that occurred in the preceding child utterance (e.g. Child : I goed there. Adult: You went where?). Analysis of probability of adult corrective repetitions revealed that the parents significantly corrected single errors (41%) more often than multiple errors (20%). In addition, the adults were differentially sensitive to errors of different types. They almost always corrected semantic errors (88%) while providing negative evidence about syntactic (32%) and

Recent Developments

in Speech to #Wren

103

phonological (34%) errors much less often. In terms of learning, if children can only process a limited amount of information, then it may be that they can only use negative information in limited contexts. That is, children may only be able to process a single correction at a time, In summary, the results of the above reported studies indicate two problems for leasability theories of language acquisition. First, the assumption that adults ignore grammatical errors is clearly false. Although the exact nature of the forms of negative evidence available (e.g. questions, repetitions, or overt corrections and verbal praise and punishment) is still undetermined, and it is still unknown just how children make use of this information, it is now well documented that differential responding does occur for well-formed and ill-formed utterances. Secondly, the results indicate that the provision of negative evidence may be partially based on processing considerations, such as working memory limitations (affected by sentence length and complexity). Interestingly, one of the proposed limitations on language learning that would help to explain the child’s supposedly “slow” rate of acquisition is the child’s limited ability to process information (Hamburger and Crain 1984). Just how such a limiting factor might be incorporated in language learning models is rarely specified, despite the fact that the limitations of processing capacity are very well documented in adult speech (e.g. Bock 1952). The results of the present report indicate that when children’s sentences follow demanding adult responses, more pragmatic and syntactic errors tend to occur. Thus children must be careful of willy-nilly accepting evidence about their errors to avoid making a syntactic correction following a mere processing problem (Nakayama and Crain 1985). Fortunately, adults seem to provide such negative evidence only in restricted contexts: Namely those situations at the boundary of the child’s language ability and when the child makes only a single error. This might also help to explain the relatively low rates of repetition and correction. Not only are adults interested in developing mature language in children, but conversation serves a myriad of other purposes such as socialization, broadly construed, and the simple maintenance of information flow between the participants. If children’s conversational partners were constantly repeating, correcting and questioning the form of the child’s speech (especially the child’s attempts at longer sentences), the resulting conversations might then be severely limited. Finally, until the nature of children’s ability to process information, and the adult tendency to provide negative evidence under specific conditions is incorporated into models of language learning, then the current batch of “learnability” theories may only be relevent for IBM mainframes (on which these powerful learning algorithms were based) and not for children,

104

hoguage

!Sciences, Volume 10, Numberl(19118)

SUMMARY

Despite the many contradictions and arguments involved in current endeavors to describe the linguistic environment of children and its possible effects, a more coherent picture is beginning to emerge. First, children are presented a set of language data that is tuned to their receptive language ability. As the child acquires expertise in the skills of language comprehension, the linguistic data presented grows in corresponding complexity. The momentto-moment adjustments are determined by cues provided by children in ongoing conversation. The actual relation between the nature of the CDS and language development will not be adequately tested until: (1) the nature of the relation between receptive and productive langauge is specified (2) sufficiently varied causal lags between maternal speech and language gains in children are investigated, and (3) appropriate mathematical models of the underlying conceptual relation between CDS and language development are employed. Lastly, the current set of formal learning approaches must recognize that children are not computers, nor are parents totally obtuse when confronted with ill-formed utterances from children. The child’s ability to handle information in limited contexts must be incorporated as central facets of any new viable theory of learning language. Thus, despite many written pronouncements to the contrary, reports of definite answers to the central questions of CDS are premature.

REFERENCES

Barnes, S., M. Gutfreund, D. Satterly, and G. Wells 1983 “Characteristics of Adult Speech which Predict Children’s Language Development,” Journal qf’ Child Language 10, 65-84. Bates, E., M. Beeghly-Smith, I. Bretherton, and S. McNew 1982 “Social Basis of Language Development: A Reassessment,” in Advances in Child Development and Behaviour Vol. 16, pp. 8-75, H. Reese and L. Lipsett (eds), New York: Academic Press. Bever, T., J. Fodor, and W. Weksel 1965 “On the Acquisition of Syntax: A Critique of “Contextual Generalization,” Psychological RevieMl 72, 467-482. Bock, K. 1982 “Toward a Cognitive Psychology of Syntax: information Processing Contributions to Sentence Formulation,” Psychological Review 89, 147.

Receot Developments lo Speech to Children

105

Bohannon, J. “Children’s Control of Adult Speech in Spanish,” Acta Paedologica in press. Bohannon, J. and K. Hirsh-Pasek 1984 “Do Children Say as They are Told? A New Perspective On The Origins and Growth of Communication, pp. Motherese,” 176-195, L. Feagans, C. Garvey and R. Golinkoff (eds), New York: Ablex Publishing. Bohannon, J. and A.L. Marquis 1977 “Children’s Control of Adult Speech,” Child Development 48, 1002-1008. Bohannon, J., L. Stanowicz, J. Ness, and A. Warren-Leubecker 1986 “Errors in Sentence Production: Evidence from a Limited Information Processor,” Paper Presented at the Conference on Human Development, Nashville, TN. Bohannon, J., E.L. Stine, and D. Ritzenberg “Motherese: The Effects of Feedback and Experience,” The Bulletin 1982 of the Psychonomic Society 19, 201-204. Bohannon, J. and A. Warren-Leubecker “Theoretical Approaches to Language Acquisition,” in Language 1985 Development, J.B. Gleason (ed.), Columbus, OH: Charles E. Merrill. Brown, R. 1973 A First Language: The Early Stages, Cambridge, MA: Harvard University Press. 1977 “The Place of Baby Talk in the World of Language, in Talking to Children: Language Input and Acquisition, C. Snow and C. Ferguson (eds), Cambridge, MA: Cambridge University Press. Brown, R. and C. Hanlon “Derivational Complexity and the Order of Acquisition in Child 1970 Speech,” in Cognition and the Development of Language, J.R. Hayes (ed.), New York: Wiley. Bruner, J. 1978 “The Role of Dialogue in Language Acquisition,” in The Childs Conception of Language, A. Sinclair, R. Jarvella and W. Levelt (eds), New York: Springer-Verlag. Chomsky, N. 1957 Syntactic Structures, The Hague: Mouton 1965 Aspects of a Theory of Syntax, Cambridge, MA: MIT Press. 1980 “On Binding,” Linguistic Inquiry 11, l-46.

106

Language Sciioces, Volume10, Number l(l988)

Cross, T.G. 1977 “Mother’s Speech Adjustments: Contributions of Selected Child Listener Variables,” in Talking to Children: Language Input and A~qu~~~f~on, C. Snow and C. Ferguson (eds), Cambridge, MA: Cambridge University Press. 1978 “Mother’s Speech and its Association with Rate of Linguistic Development in Young Children,” in The Development of Communication, N. Waterson and C. Snow (eds), New York: Wiley. Culbertson, G. and L. Caporeal 1983 “Baby Talk to the Elderly: Complexity and Content of Messages.” Personality

and Social Ps*v~~~o~ogyBulietin 9, 305-3 12.

DeCasper, A. 1980 “Newborn Preference for Maternal Voice: An Indication of Early Attachment,” Paper Presented at the meeting of the Southeastern Conference on Human Development, Alexandria, VA. Demetras, M., K. Post, and C. Snow 1986 “Feedback to First Language Learners: The Role of Repetitions and Clarification Questions,” Journal qf’ Child Language 13, 275292. DePauIo, B. and L. Coleman “Talking to Children, Foreigners, and Retarded Adults,” in press. DePaulo, B. and J. Bonvillian 1978 “The Effect on Language Development of the Special Characteristics of Speech Addressed to Children,” Journal of‘ Psycholinguistic Research

7, 189-2 11.

Ferguson, C. 1975 “Towards a Characterization of English Foreigner Talk,” Anfhropological Linguistics 17, 1-17. 1977 “‘Baby-talk as a Simplified Register,” in Talking to Children . Language Input and Acquisition, C. Snow and C. Ferguson (eds). Cambridge, MA: Cambridge University Press. Fernald, A. 1984 “The Perceptual and Affective Salience of Mothers’ Speech to Infants,” in The Origins and Growth of ~o~munic~t~~n, L. Feagans, C. Garvey and R. Golinkoff (eds), Norwood, NJ: Ablex Publishing. Friedlander, B. 1970 “Receptive Language Development in Infancy,” Merrill-Palmer Quarterly

16, 7-5 1.

Furrow, D., K. Nelson, and H. Benedict 1979 “Mothers’ Speech to Children and Syntactic Development:

Some

Recent Developments lo Speech to Children

107

Simple Relationships,” Journal of Child Language 6, 423442. Gallagher, T. 1977 “Revision Behaviours in the Speech of Normal Children Developing Language,” Journal of Speech and Hearing Research 20, 303-3 18.

Garvey, C. “The Contingent 1977 Interaction,

Act in Conversation,”

in

Conversation and the Development of Language,

Query: A Dependent

M.

Lewis and L. Rosenblum (eds), New York: J. Wiley. George, B. and M. Tomasello 1984 “The Effect of Variation in Sentence Length on Young Children’s Attention and Comprehension,” First Language 5, 115-l 28. Gleason, J. 1977 “Some Notes on Feedback,” in Talking to Children: Language Input and Acquisitions, C. Snow and C. Ferguson (eds), Cambridge, MA: Cambridge University Press. Gleason, J. and S. Weintraub 1978 “Input Language and the Acquisition of Communicative Competence,” in Children’s Language, Vol. 1, K. Nelson (ed.), New York: Gardiner Press. Gleitman, L., E. Newport, and H. Gleitman 1984 “The Current Status of the Motherese Hypothesis,” Journal of Child Language 11, 43-80. Gleitman, L. and E. Wanner 1982 “Language Learning: State of The State of The Art,” in Language Acquisition: The State of The Art, E. Wanner and L. Gleitman (eds), Cambridge, MA: Cambridge University Press. 1984 “Current Issues in Language Learning,” in Developmental Psychology: An Advanced Textbook, M. Bornstein and M. Lamb (eds), Hillsdale, NJ: Lawrence Erlbaum Publishers. Goldin-Meadow, S. 1982 “The Resilience of Recursion,” in Language Acquisition : The State of The Art, E. Wanner and L. Gleitman (eds), Cambridge, MA: Cambridge University Press. Goldin-Meadow, S. and H. Feldman 1977 “The Development of Language-like Communication Without a Language Model,” Science 197, 401403. Golinkoff, R. and G. Ames 1979 “A Comparison of Father’s and Mother’s Speech to Their Young Children,” Child Development 50, 28-32.

Language !Scieoces, Volume 10, Number l(1988)

108

Hamburger,

H. and S. Crain

1984

“Acquisition

Hirsh-Pasek,

of Cognitive

1982

1984

“Brown

Hoff-Ginsberg, 1985

matical E.

& Hanlon Forms,”

Revisited:

Mothers’

Sensitivity

to Ungram-

Journal qf Child Language 11, 8 l-88.

“Relations Between Discourse Properties of Mother’s Speech and Their Children’s Syntactic Growth,” Journal of Child Language 12, 367-385. “Function and Structure in Maternal Speech: Their Relation to the

1986

Child’s Development 155-163. Hoff-Ginsberg,

James,

Journal of Child Lang-

“Doggerel: Motherese in a New Context,” uage 9, 229-237. K., R. Treiman, and M. Schneiderman

Hirsh-Pasek,

1987

Cognition 17, 85-l 36.

Compiling”,

K. and R. Treiman

of Syntax,”

E. and M. Shatz “Linguistic Input and the Child’s Psychological Bulletin 92, 3-26.

Developmental

Psychology 22,

Acquisition

of

Language,”

L. and K. Singh “An Introduction to the Logic, Assumptions, and Basic analytic Procedures of Two-stage Least Squares,” Psychological Bulletin 85, 1104-l 122.

1978

James, L. and L. Tetrick 1980 “Confirmatory

Lederberg, 1982

Job Perceptions 71, 77-82. A. “A Framework Modifications,”

Analytic

Tests

to Job Satisfaction,”

for Research in Language

Thought and Culture, S. Kuczaj Moerk, E. 1975 1983 Nakayama, 1985

of Three

Causal

Journal

Models

Relating

qf Applied Psycholog),

on Preschool Development, (ed.), Hillsdale,

Children’s Speech Vol. 2, Language, NJ: Erlbaum.

“Verbal Interactions Between Children and Their Mothers During the Preschool Years,” Developmental Psychology 11, 788-794. The Mother of Eve-as a First Language Teacher, Norwood, NJ: Ablex. M. and S. Crain “Performance Factors in Children’s Spontaneous duction,” Paper Presented at the Boston University Development, Boston.

Sentence Proon Language

Recent Developamts

In Speech to Children

109

Nelson, K.E., M. Denninger, J. Bonvillian, B. Kaplan and N. Baker 1983 “Maternal Input Adjustments and Non-adjustments as Related to Children’s Linguistic Advances and the Language Acquisition Theories,” in The Development of Oral and Written Languages: Readings in Developmental and Applied Linguistics, A. Pelligrini and T. Yawkey (eds), Norwood, NJ: Ablex. Newport, E., L. Gleitman, and H. Gleitman 1977 “Mother I’d Rather Do It Myself: Some Effects and Non-effects of Motherese,” in Talking to Children: Language Input and Acquisition, C. Snow and C. Ferguson (eds), Cambridge, MA: Cambridge University Press. Pratt, M., D. Bumstead, and N. Raines Staff Speech to the Institutionalized Retarded: 1976 “Attendant Language Use as a Measure of the Quality of Care,” Journal of Child Psychology and Psychiatry 17, 133-144. Pinker, S. 1979 “Formal Models of Language Learning,” Cognition 7, 217-283. “The Bootstrapping Problem in Language Acquisition,” in 1987 Mechanisms of Language Acquisition, B. MacWhinney (ed.), Hillsdale, NJ: Lawrence E Earlbaum. Rileigh, K. 1973 “Children’s Selective Listening to Stories: Familiarity Effects Involving Vocabulary, Syntax, and Intonation,” Psychological Reports 33, 255-266.

Sachs, J. and J. Devin 1976 “Young Children’s Use of Age Appropriate Speech Styles in Social Interaction and Role-playing,” Journal of Child Language 3, 81-98. Sachs, J. and M. Johnson 1972 “Language Development in a Hearing Child of Deaf Parents,” Paper Presented at the International Symposium on First Language Acquisition, Florence, Italy. Shatz, M. and R. Gelman 1973 “The Development of Communication Skills: Modifications in the Speech of Young Children as a Function of Listener,” Monographs of the Society for Research in Child Development 38, (5, Serial No. 152.) Snow, C.E. 1972 “Mother’s Speech to Language Learning Children,” Child Development 43. 549-565. LBC

10/1-H

110

Laqup~e

Scieaces, Volume 10, Numberl(1988)

Snow, C.E. and C.A. Ferguson (eds) 1977 Talking to Children: Language Input and Acquisition, Cambridge, MA: Cambridge University Press. Snow, C.E. 1979 “The Role of Social Interaction in Language Acquisition,” in Children’s Language and Communication: 12th Minnesota Symposium on Child Psychology, A. Collins (ed.), Hillsdale, NJ: Erlbaum. 1981 “Social Interaction and Language Acquisition,” in Child Language. An International Perspective, P. Dale and D. Ingram (eds), Baltimore, MD: University Park Press. Stine, E.L. and J. Bohannon “Imitations, Interactions and Language Acquisition,” Journal of 1983 Child Language

10, 589-604.

Tomasello, M. 1988 “The Role of Joint Attentional Processes in Early Language Development,” Language Sciences 10, 67-86. Warren-Leubecker, A. and J. Bohannon 1982 “The Effects of Expectation and Feedback on Speech to Foreigners,” Journal of Psycholinguistic Research 11, 207-2 15. “The Effects of Verbal Feedback and Listener Type on the Speech 1983 of Preschool Children,” Journal of Experimental Child Psychology 35, 54&548.

“Intonation Patterns in Child-directed Speech: Mother-Father Differences,” Child Development 55, 154 l-l 548. 1985 “Language in Society: Variation and Adaptation,” in The Development of Language, pp. 331-367, J. Berko-Gleason (ed.), Columbus, OH: Charles E. Merrill. Wexler, K. and P. Cullicover 1980 Formal Principles of Language Acquisition, Cambridge, MA: MIT Press. Wexler, K. “A Principle Theory for Language Acquisition,” in Language 1982 Acquisition : The State of The Art, E. Wanner and L. Gleitman (eds), Cambridge MA: Cambridge University Press. Whitehurst, G. in Handbook of Developmental Development,” 1982 “Language Psychology, B. Wolman (ed.), Englewood Cliffs, NJ: Prentice-Hall. Wilcox, J. and E. Webster “Early Discourse Behavior: An Analysis of Children’s Responses 1980 to Listener Feedback,” Child Development 51, 1120-l 125. 1984