FIRST WORDS IN THE SECOND YEAR:
CONTINUITY, STABILITY, AND MODELS OF
CONCURRENT AND PREDICTIVE
CORRESPONDENCE IN VOCABULARY AND
VERBAL RESPONSIVENESS ACROSS AGE AND
CONTEXT
Marc H. Bornstein
National Institute of Child Health and Human Development
Catherine S. Tamis-LeMonda
New York University
O. Maurice Haynes
National Institute of Child Health and Human Development
This prospective longitudinal study assessedchildren's and mothers' productive vocabulary and mothers'
verbal responsesto children's exploratory and vocal behavior in spontaneousspeech, and evaluated multiple relations in those measures in two contexts (play and mealtimes) at two child ages (13 and 20
months). Continuity, stability, and several models of concurrent and lamed child-mother correspondences were evaluated. Child and mother vocabulary increased across the second year, but did so differently in the two contexts; vocabulary of both showed significant stability of individual variation across
context and age. Developmental change in maternal verbal responsespredicted child vocabulary (maternal vocabulary did not), and developmental change in child vocabulary predicted maternal responses.The
results support a model of specificity in mother-child language exchange and child vocabulary growth.
Child language Mother language Methodology Developmental Models
• Dr. Marc H. Bornstein, Child and Family Research, National Institute of Child Health and Human Development,
Building 31--Room B2B15, 9000 Rockville Pike, Bethesda MD 20892-2030; Phone: 301-496-6832; Fax: 301-4962766; e-mail: Marc H [email protected]
INFANT BEHAVIOR & DEVELOPMENT22 (1), 1999, pp. 65-B5
Copyright © 1999 ElsevierScience Inc.
ISSN 0163-6383
All rights of reproduction in any form reserved.
66
INFANT BEHAVIOR & DEVELOPMENT Vol. 22, No. 1, 1999
This prospective longitudinal study was
designed to investigate multiple developmental aspects of young children's first words as
used in spontaneous speech. The data consist
of productive vocabulary in child and maternal
speech, as well as maternal responsiveness, all
taken from child-mother conversations in two
naturalistic contexts, play and mealtimes, at
two ages during the child's second year, 13
and 20 months. The central theoretical question that motivated this study concerned the
relative roles of maternal vocabulary and verbal responsiveness in predicting children's
verbal development at each age in and across
this time period. In addition, several basic
developmental psycholinguistic questions
were addressed, including the following: How
are child and mother productive vocabulary
affected by changes in child age and by
changes in context of assessment? Is individual variation in child and mother vocabulary
stable across age and across context in the second year? Do child and mother vocabulary
covary at different ages and in different contexts? An assumption underlying this study
was that language measures in child and
mother would relate to one another in specific
rather than general ways.
Vocabulary is a key marker in children's
language development; it is a prominent part
of the language of children that parents hear
and attend to, and of the language parents and
others offer to children. Vocabulary predicts
success in learning to read (Chall, Jacobs, &
Baldwin, 1990); and vocabulary is a central
component of intelligence tests (Neisser et al.,
1996). Thus, changes in child (and caregiver)
productive vocabulary in spontaneous speech,
and factors that may influence those changes,
are of interest. We, therefore, undertook to
study developmental stability and change
(between two age periods and two contexts) as
well as directionality and specificity of
mother-to-child and child-to-mother mutual
influences vis-a-vis vocabulary development
in children.
We recorded and compared productive
vocabulary in children's and mothers' sponta-
neous speech, and contrasted sheer vocabulary
with a related key feature of maternal language, contingent verbal responsiveness.
Vocabulary was operationalized as the number
of different word roots used in 15-min language samples. Vocabulary growth rates in
children are marked by substantial individual
differences (e.g., Bates, Dale, & Thai, 1995; L.
Bloom, 1993; Bornstein & Haynes, 1998;
Tamis-LeMonda, Bornstein, Baumwell, &
Damast, 1996). Language development generally entails innate abilities and biological constraints (Gleitman & Wanner, 1988; Pinker,
1994), but to acquire vocabulary children must
be exposed to the words of a language: That is,
children depend on "pairings of sound patterns
with meanings" (Huttenlocher, Haight, Bryk,
Seltzer, & Lyons, 1991, p. 236). The child's
acquisition of vocabulary is therefore influenced by variation in language exposure:
Moerk (1980), for example, argued that frequency of parental speech relates to child language acquisition. The amount of speech
children hear predicts their language development (Barnes, Gutfreund, Satterly, & Wells,
1983; Hart & Risley, 1992; McCartney, 1984):
A high total volume of child-directed speech
positively correlates with child language
(Hoff-Ginsberg & Shatz, 1982; Pine, 1994);
mothers who produce more speech have toddlers who produce more words in the laboratory (Smolak & Weinraub, 1983; Tomasello,
Mannle, & Kruger, 1986); and mothers of"referential" children (whose vocabulary tends to
be characterized by a high proportion of nominals) themselves use more nominals (Goldfield, 1985/1986). Overall amount of parent
speech input accounts for variation in children's acceleration of vocabulary growth
(Huttenlocher et al., 1991), and Scarr and
Weinberg (1978) reported that the correlation
between the vocabulary scores of adoptive
mothers and children was as high as that
between the vocabulary scores of biological
mothers and their children, clearly supporting
independent experiential effects.
A significant dimension of parenting is
responsiveness -- caregivers' prompt, contin-
ChildLanguagein Year2
gent, and appropriate reactions to children's
communicative and exploratory overtures
(Bomstein, 1989a). Not only has parental
responsiveness been acknowledged as a powerful general factor in child development since
Bowlby (1969) and Ainsworth (Ainsworth,
Blehar, Waters, & Wall, 1978)--it is regularly
associated with advances in the growth of
skills in many domains of development (e.g.,
Bradley, 1989)--but caregiver verbal responsiveness (contra intrusiveness; Baumwell,
Tamis-LeMonda, & Bornstein, 1997) is
thought to play a pivotal role in the child's
acquisition of language (e.g., L. Bloom, 1993;
L. Bloom, Margulis, Tinker, & Fujita, 1996;
Hoff-Ginsberg & Shatz, 1982; van IJzendoorn,
Dijkstra, & Bus, 1995).
Empirically, Rheingold, Gewirtz, and Ross
(1959) demonstrated that vocalizations in
babies as young as 3 months of age could be
operantly conditioned by providing contingent
social reinforcement. K. Bloom and her associates (1979; K. Bloom, Russell, & Wassenberg,
1987), studying the effects of turn-taking in
mother-infant conversation on infant vocalization and on the quality of subsequent mother
vocalization, found that, when adults mainmined a prototypic conversational give-andtake pattern, 3-month-old infants produced a
relatively higher ratio of speech-like to nonspeech-like sounds and that adult responsiveness facilitated a speak-listen pattern of
vocalizing in the infant even in the absence of
a verbal component of the adult's response.
Caregiver verbal responsiveness to infants also
predicts later language functioning, including
vocabulary comprehension at 1 year (Baumwell et al., 1997; Bornstein & Tamis-LeMonda, 1989; Tamis-LeMonda et al., 1996);
receptive vocabulary, responsiveness to mothers' utterances, and scores on the Mental
Development Index of the Bayley Scales of
Infant Development at 2 years (Beckwith &
Cohen, 1989); Stanford-Binet at 3 and 4 years
(Bakeman, Adamson, Brown, & Eldridge,
1989); Wechsler Preschool and Primary Scale
oflntelligence (WPPSI) at 4 years (Bornstein
& Tamis-LeMonda, 1989); and Wechsler
67
Intelligence Scale for Children (WISC) at 12
years (Beckwith & Cohen, 1989); indeed, caregiver responsiveness accounts for the age at
which children achieve a number of different
verbal milestones (Tamis-LeMonda, Bornstein, Kahana-Kalman, Baumwell, & Cyphers,
1998). These effects are not limited to Western
childrearing situations: Maternal verbal
responsiveness at 4 months predicts Canel
Infant Test and Peabody Picture Vocabulary
Test scores in the second year in Japanese children (Bornstein, Miyake, Azuma, TamisLeMonda, & Toda, 1990).
The literatures on exposure to vocabulary
and on responsiveness demonstrate that maternal speech influences child vocabulary growth,
but they do not disentangle which (if either)
may be the more influential, nor do they clarify
the process(es) by which vocabulary and/or
responsiveness might be effective. For example, the literature does not address questions of
how diversity of vocabulary use or verbal
responsiveness to child exploration and vocal
production by caregivers is most effectively
distributed through time to influence child
vocabulary growth. The first purpose of this
longitudinal study was to compare these components of maternal language and to evaluate
models of different temporal processes.
In undertaking this comparison, we sought
additionally to evaluate age and context effects
on child and mother vocabulary and mothers'
verbal responses in spontaneous speech. We
therefore examined developmental continuity
and stability in productive vocabulary in both
child and mother; that is, we collected information on child and mother vocabulary usage
in the same dyads at two ages in the child's
second year and examined simple age effects.
Another aim was to examine the role of context
in vocabulary production and verbal responsiveness. To do so, we researched child and
mother language in different circumstances in
the home. The natural setting of the home has
obvious advantages of ecological validity
(e.g., Dunn & Wooding, 1977; Green,
Gustafson, & West, 1980); in this normally
comfortable situation, a high degree of consis-
68
INFANTBEHAVIOR& DEVELOPMENT Vol.22, No. 1, 1999
tency on the part of conversants can be
expected. Nonetheless, behaviors of all sorts
vary, even within the home setting, depending
on circumstances (Hoff-Ginsberg, 1991), and
assessments of language observed in different
circumstances even within a child's common
daily experiences can be expected to yield different patterns. Play and mealtimes, for example, call forth different goals, tasks, and
stances from interactants/conversants, and perhaps different characteristics of language on
the parts of child and mother: Play is a prime
context for verbal exchange, whereas mealtimes are more functional and have a specific
end goal. Insofar as context helps to shape
child and/or mother language, examination of
context effects permits or limits generalizability of findings about language development.
Finally, the study also concerned itself with
three more general developmental issues in
child language: group continuity, individual
stability, and partner interrelationships. Continuity describes consistency in the absolute
level of group performance across age or context. Continuity would be indicated by children's productive vocabulary appearing in the
same average amount when children are young
and again when they are older, when at play
and in mealtime. We naturally expected the
mean level of child productive vocabulary in
spontaneous speech to increase with child age;
but we were less certain about change or the
direction of change in maternal vocabulary
across this specific age period (in this period
mothers might use more or less vocabulary in
relation to child production; Nelson, Bonvillian, Denninger, Kaplan, & Baker, 1984). We
also expected group mean differences in child
and in mother vocabulary and maternal verbal
responses between contexts, speculating that
conversants/interactants would use more
vocabulary, and mothers would be more verbally responsive, at play than in mealtimes.
The second general developmental issue
concerned stability. Stability describes consistency in the relative ranks of individuals with
respect to a measure over age or across contexts. Stable productive vocabulary in chil-
dren, for example, would mean that
vocabulary occurs with the same relative frequency in individual children across age (when
they are young and again when they are older)
or across context (at play and in mealtimes).
The extent to which stability represents an
attribute of the individual or depends on circumstances remains unclear in the absence of
both cross-age and cross-context data. As it
has been argued that productive vocabulary is
sensitive to experience (see above), vocabulary might be stable only in individuals with
stable language environments. On the other
hand, communicative development is also
ascribable, at least in part, to biological and
maturationai characteristics in the individual
(e.g., Hardy-Brown, Plomin, & DeFries, 1981;
Pinker, 1994), and this argument anticipates
that child and mother vocabulary alike would
be at least moderately stable across age and
context independent of partner input.
The study's longitudinal design permitted
examination of a third set of general developmental issues in children's vocabulary development, viz. relations in child-mother dyads at
and between two points in the child's second
year. Correspondence describes consistency in
the rank-order status of pairs of individuals on
some measure; correspondences may be concurrent or lagged. Correspondences define
mutual influences between child and mother.
However, it is possible to specify correspondences further in order to evaluate the nature of
unique effects of one member of the dyad on
the other over time (e.g., Bornstein & TamisLeMonda, 1990; Bradley, Caldwell, & Rock,
1988).
Four models of mutual influence were
assessed in this study: In a simultaneous relations model, maternal productive vocabulary
would relate to child productive vocabulary at
a particular point in development, independent
of stability in child productive vocabulary to
that point and independent of earlier relations
between mother and child productive vocabulary. Three additional models assessed the
nature of the effects of one partner on the other
across time. In a developmental average
Child Languagein Year2
effects model, early and later maternal productive vocabularies are considered together, and
their mean over time exerts a significant effect
on child vocabulary independent of stability in
the child. In a developmental change effects
model, the increment (or decrement) in maternal vocabulary from an earlier to a later point
in time exerts a significant effect on child
vocabulary independent of stability in child
vocabulary. In a developmental consistency
effects model, the degree to which mothers
maintain their level of vocabulary from earlier
to later points in time exerts a significant effect
on child vocabulary independent of stability in
child vocabulary.
Naturally, conversational data occur in
interactive situations; to examine spontaneous
speech and to isolate partner effects in these
models, we compared zero-order patterns of
child and mother productive vocabulary with
patterns controlling for partner input. We also
distinguished among several potential temporal processes that might underlie lagged patterns of association between child and mother
productive vocabulary and maternal responsiveness. These included average, change, and
consistency models of developmental effects.
METHOD
Participants
Thirty children (15 males and 15 females)
and their mothers participated in two home
observations scheduled 7 months apart. Dyads
were recruited from private obstetric and pediatric groups in a large metropolitan area. Children averaged 13.2 months of age (SD = 0.1) at
the time of the fn'st observation and 20.4
months of age (SD = 0.1) at the time of the second observation. Children were all firstborn,
Caucasian, term at birth (M weight = 3.39 kg;
M length = 51.0 era), and had been healthy
(except for minor illnesses) from birth and
throughout the course of the study. Mothers
averaged 33.4 years of age (SD = 4.1) at the
time of the child's birth. Households were of
69
middle- to upper-socioeconomic status (M =
59.5, SD = 5.7, on the Hollingshead Four Factor Index of Social Status, 1975; Gottfried,
1985); English was the only language spoken
at home; and most mothers (90%) had completed college. Families of boys and girls did
not differ on any sociodemographic characteristics, and no systematic relations emerged in
this sample between sociodemographic characteristics and language measures. The literature on gender effects in language acquisition
is mixed: Preliminary analyses of variance
(ANOVAs) showed no main effects of gender
or interactions of gender with age or context in
this data set, and preliminary inspection of correlations showed no differences between boys
and girls or mothers of boys and girls; therefore, gender as a between-subjects factor was
not considered further.
The study focused on productive vocabulary and verbal responsiveness in spontaneous
speech in the second year, a time during which
children normally make extraordinary developmental strides. Among the main tasks of this
time are the achievement of communicative,
symbolic, and self-regulatory capacities: Children exhibit rapid increases in receptive and
productive language when they begin to understand and to say sound sequences which function as true "naming," and they shift away
from a "context-restricted," purely performative use of words or phrases to adopt "flexible"
usage across contexts (Snyder, Bates, &
Bretherton, 1981). Children were initially
observed at 13 months: At this time, about half
of all children on average are producing their
first words and are advanced in language comprehension. Children were seen again at 20
months: By this time, about half of all children
on average have increased productive vocabulary; they are substantially regular in the ways
they express possession, location, and action;
and they combine words (L. Bloom et al.,
1996; de Villiers & de Villiers, 1999). For
example, L. Bloom (1993) reported that some
children acquire their first words at about 9 or
10 months of age, have 25 different words by
14 months, and show a great increase in the
70
INFANT BEHAVIOR & DEVELOPMENT Vol. 22, No. 1, 1999
number of different words at 17 months. At
both ages, measures of language are typically
characterized by substantial individual variation which appears to be a valid index of later
linguistic and/or cognitive functioning (see
Bates et al., 1995; Reynell & Huntley, 1985).
Procedure
Home visits were scheduled during times
when children were alert and rested, and child
behavioral state was not a factor in these evaluations because children were alert, rested, and
engaged in both contexts at both ages. At 13
and again at 20 months, dyads were videotaped
for at least 15 min at free play and 15 min in a
meal. In each condition, mothers were asked to
remain with their children, to disregard the
observer's presence insofar as possible, and to
do whatever they would ordinarily at that time
in that context. Mothers were told at the outset
that the investigators were interested in broad
aspects of children's development and that,
because play and meals are so common in children's everyday experiences, families would
be videotaped in both contexts. For each play
session, similar sets of toys were placed on the
floor in front of the child and mother (a teapot
and cover, spoons, cups and saucers, clowndoll, toy telephone, book, ball, blocks, nesting
barrels, shape sorter, and toy vehicle). The
meal was taped after play.
Vocabulary and Verbal Responsiveness
at 13 and 20 Months
Data on children's and mothers' productive
vocabulary derived from transcripts of spontaneous speech from the play and mealtime sessions at both 13 and 20 months. The first 15
min available from videotapes were transcribed verbatim; each transcript was then
checked against the videotape for accuracy by
researchers other than the original transcriber.
Coding of all the transcripts followed conventions of the Systematic Analysis of Language
Transcripts (SALT; Miller & Chapman,
1993). Following SALT rules, an utterance
was defined as a unit of speech indicated by
intonation and/or pauses. Multiple utterances
per turn are possible in a conversation. The initial transcripts included phonetic approximations of every utterance. Coders credited a
word if the word was intelligible, taking context (gestures, mother's interpretation, subsequent repetition of the word in a similar
context) into account. Accurate articulation
was not required to credit the child. Utterances
that were unintelligible to coders and utterantes upon whose content coders could not
agree were not counted. Measures of productive vocabulary were computed as the total
numbers of different word roots children and
their mothers produced in all utterances.
All codable maternal utterances in the transcripts were also classified as responsive or not
by checking the content of the transcribed
utterance against contextual and timing cues in
the videotapes of the session. The measure of
maternal verbal responses was modified from
Bornstein et al. (1992) and is detailed in
Baumwell et al. (1997). Briefly, responsiveness was coded whenever a mother verbally
responded contingently and appropriately (not
simply contiguously) to her child's exploratory or vocal behavior within 5 s following
the child act. For a mother to be credited with
a verbal response, the following conditions
had to be met: (1) the child had to exhibit a
change in either exploratory or communicative
behaviors, including, respectively, bids toward
mother or object exploration or play or nondistress vocalization. (2) The mother had to demonstrate a meaningful change in her verbal
behavior subsequent to the target child behavior (e.g., child picks up ball, and mother says
"throw it to me"). (3) The mother's new
behavior had to depend on the child's target
behavior. Maternal comments which were reprimands or included the word "no" (unless
mother was using a term descriptively: e.g.,
"No more barrels.") were not included. Maternal verbal responses were calculated at each
age in each context by summing the frequency
of maternal responses to all target child acts.
71
Child Language in Year 2
TABLE 1
Descriptive Statistics for Language Measures for Child and
Mother at 13 and 20 Months in Play and at Mealtime
Vocabulary
A. Child
13 months
Play
Mealtime
20 months
Play
Mealtime
B. Mother
13 months
Play
Mealtime
20 months
Play
Mealtime
Range
VerbalResponses
Mean
5D
Range
Mean
SD
3.8
3.7
0 - 16
3.7
4.5
0 - 21
52.8
23:5
27.8
16.3
9 - 98
4 - 62
182.3
168.9
33.3
36.1
114 - 272
116 - 280
51.3
51.6
17.1
18.5
19 - 90
20 88
191.9
190.4
40.3
44.2
145 - 293
127 - 313
83.0
65.6
30.4
20.0
33 - 154
31 - 106
Ninety-two transcripts, randomly selected
from a separate and independent sample o f
mother-child interactions at 20 months, were
coded by two trained coders, and agreement
(intraclass correlations: ICC) between coders
was as follows: for child vocabulary I C C =
.992, and for mother vocabulary I C C = .997.
Three trained coders, unaware o f the quantitative characteristics o f children's language data,
coded the 120 videotapes for responsiveness.
Random checks at each age for each coder
were used to ensure reliability: M = 82%
(range = 73 - 91%). All play sessions lasted a
minimum o f 15 min; some meals did not last
15 min. Both productive vocabulary and mothers' verbal responses were prorated to 15 min
where necessary. The total amount o f time prorated in both play and meal contexts at both 13
and 20 months was 1932 s, which is 1.8% o f
total recording time across all dyads in all conditions at the two ages.
Prior to any formal analysis, univariate distributions for productive vocabulary and
responses were checked for outliers and normalcy (Fox, 1997). In different preliminary
regression analyses, 1 or 2 cases (not necessarily the same ones in each analysis) emerged as
influential outliers, and were selectively
deleted from final analyses to maximize the
sample size. Square root transformation nor-
-
malized productive vocabulary, and analyses
were therefore conducted on square root transformed data; for clarity, however, untransformed means are presented in tables of
descriptive statistics. N o transformation was
necessary for maternal verbal responses.
RESULTS
W e first report descriptive statistics for child
and mother productive vocabulary and for
maternal verbal responses in each o f the two
contexts at each o f the two ages. Analyses of
these longitudinal data are then organized
around issues o f continuity and stability o f child
and mother productive vocabulary and maternal
verbal responsiveness at play and in mealtimes
between 13 and 20 months and on correspondences in child and mother in each context at
each age, culminating in the evaluation of
unique 13- to 20-month lagged models o f verbal
interaction between children and their mothers.
Descriptive Statistics
Table 1 presents descriptive statistics
(means, standard deviations, and ranges) for
child and mother language measures at 13 and
20 months at play and in mealtime. Children
INFANT BEHAVIOR & DEVELOPMENT
72
Vol. 22, No. 1, 1999
TABLE 2
Analyses of Variance for Continuity in Language Measures for Child and
Mother across Age and Context
Effect
A. Child
Vocabulary
Age
F(1,29)
384.15***
Context
52.08***
Age x Context
41.21 ***
B. Mother
Vocabulary
Age
Verbal Responses
Context
Age x Context
Age
Context
A~e x Context
Simple Effects
Age at Play
Age in Mealtime
Context at 13 Months
Context at 20 Months
t:(1,29)
424.88***
145.50"**
.08
72.57***
5.13*
2.99
3.17
49.69***
7.21 *
Age at Play
55.26**
Age in Mealtime
Context at 13 Months
Context at 20 Months
11.56"*
.01
13.81 ***
11.01"*
*p =: .OS;**p ==.01; ***p ==.001
and their mothers showed substantial variation
in these measures at both ages, M coefficient
of variation = 3.07, range = .84 to 5.47.
Continuity across Age and Context
In repeated-measures ANOVAs with age
and context as within-subjects variables, children and mothers alike changed in their productive vocabulary across age and context.
Table 2 shows results of ANOVAs for children
and mothers, illustrating continuity and change
in these language measures between 13 to 20
months.
In Mothers
Mothers' vocabulary also increased as their
children grew from 13 to 20 months (Table
2B), but did not differ by context. For verbal
responses, a significant age-by-context interaction emerged: In both contexts, mothers
responded more at 20 months than at 13
months; however, mothers responded more to
their children at play than in mealtimes only at
20 months (Table 2B). In mothers, vocabulary
and verbal responses showed different patterns
of change with children's development.
Stability across Age
In Children
A significant age-by-context interaction
emerged for vocabulary in spontaneous
speech. Simple effects of age indicated, as
expected, that vocabulary increased significantly from 13 to 20 months in both contexts
of play and mealtimes (Table 2A). However,
simple effects of context were significant only
at 20 months: Children used more vocabulary
at 20 months at play than in mealtimes, but
contextual differences were not evident at 13
months.
Stability in children's vocabulary and in
mothers' vocabulary and verbal responses, calculated across age, was estimated by zeroorder correlations and by part correlations.
In Children
Table 3A 1 shows zero-order stability correlations: Children's vocabulary was stable in
both contexts between 13 and 20 months and
differed statistically from zero. Hierarchical
multiple regression analyses also supported the
Context
.65***
.31"
Verbal Responses
Covariate(s)~
Context
1.
Child
Vocabulary
at 20 Months
Play1
2. Child Vocabulary at 13 Months
Mealtime 1. Child Vocabulary at 20 Months
2. Child Vocabulary at 13 months
Play 1. Child Vocabulary at 20 Months
2. Child Vocabulary at 13 Months
Mealtime 1. Child Vocabulary at 20 Months
2. Child Vocabulary at 13 Months
Vocabulary
.48**
.43**
Context
Covariate(s)a
Play 1. Mother Vocabulary at 20 Months
2. Mother Vocabulary at 13 Months
Mealtime1 1. Mother Vocabulary at 20 Months
2. Mother Vocabulary at 13 Months
Play2 1. Mother Verbal Responses at 20 Months
2. Mother Verbal Responses at 13 Months
Mealtime 1. Mother Verbal Responses at 20 Months
2. Mother Verbal Responses at 13 Months
Vocabulary
.56***
.53**
~One outlier excluded: n = 29.
2Two outliers excluded: n = 28.
aCovariate(s) entered in separate, ordered steps prior to predictor.
*p s .OS; **p == .01; ***p s .001,
b. Verbal Responses
Mother Predicted
Measure at 20 months
a. Vocabulary
Context
Play1
Mealtime
2. Hierarchical Regression
B. Mother
1. Zero-order correlations
b. Vocabulary
a. Vocabulary
Play
Mealtime 1
2. Hierarchical Regression
Child Predicted Measure
at 20 months
A. Child
1. Zero-order correlations
.47
.81
.40
3. Mother Verbal Responses
3. Mother Verbal Responses
.48
3. Child Vocabulary
3. Mother Vocabulary
.80
3. Child Vocabulary
~
.50
.52
3. Child Vocabulary
Predictor at 13 Months
3. Mother Vocabulary
.56
~
3. Child Vocabulary
Predictor at 73 Months
.13
.34
.21
R2 Change
.23
.19
.27
.25
.28
R2 Change
TABLE 3
Stability of Language Measures in Child and Mother within Context across Age: 13 months to 20 months
F(1,26) = 5.22*
F(1,26) = 26.12"**
F(1,26) = 7.08*
F Change
F(1,25) = 8 . 2 9 * *
F(1,26) = 7.70**
F(1,24) = 16.99"**
F(1,25) = 9.36**
F Change
F(1,26) = 11.59**
r~
74
INFANT BEHAVIOR& DEVELOPMENT Vol. 22, No. 1, 1999
TABLE4
Stability of Language Measures in Child and
Mother at Two Ages across Context: Play and Mealtime
Vocabulary
13 Months
.58"**
20 Months
.70" **
13 Months
20 Months
.65***
.65***
VerbalResponses
B. Mother
.40*
.55***
*p =~ .05; ***p == .001 (one-tailed tests)
stability of child vocabulary when mother
vocabulary at 13 and 20 months was held constant: Table 3A2 shows stability in child vocabulary (R2 change = square of the part
correlation) when mothers' vocabulary at 20
months (Step 1) and at 13 months (Step 2) were
entered first in separate analyses for play and
mealtime. That is, children's vocabulary at 13
months predicted their vocabulary at 20 months
in both play and mealtime contexts controlling
for 20-month concurrent and 13-month lagged
maternal vocabulary (Table 3A2a). An
increase of one standard deviation in children's
vocabulary at 13 months, holding mothers'
vocabulary constant, was associated with an
average increase of .56 standard deviations in
children's vocabulary at 20 months. The same
stability relations held for children's vocabulary over and above their mothers; concurrent
and lagged verbal responses (Table 3A2b).
Thus, on a relatively conservative account, stability in child productive vocabulary in spontaneous speech obtained over and above maternal
vocabulary and responsiveness.
In Mothers
Table 3B1 shows zero-order stability of
mothers' vocabulary and verbal responses in
the two contexts across their children's second
year; mothers were also highly consistent.
Hierarchical multiple regression analyses supported the stability of both measures of maternal language: Mothers were stable in their
vocabulary in spontaneous speech between 13
and 20 months at play and in mealtimes over
and above their children's 20- and 13-month
productive vocabulary (Table 3B2a). Mothers'
verbal responses were also stable between 13
and 20 months at play and in mealtimes independent of their children's 20- and 13-month
productive vocabulary (Table 3B2b). Thus,
significant unique stability from 13 to 20
months in two aspects of maternal language
emerged over and above contemporary as well
as antecedent child vocabulary.
Stability across Context
In Children
Table 4A shows that children were highly
stable in spontaneous vocabulary production
across contexts of play and mealtime at 13
months and at 20 months.
In Mothers
Table 4B shows that, like their children,
mothers were also highly stable across contexts in vocabulary production and in verbal
responses at 13 months and at 20 months.
Concurrent Correspondences
Children and their mothers covaried in
spontaneous vocabulary at 13 months in mealtimes, r(27) = .43, p < .01, but did not covary
at 13 months at play or at 20 months in either
of the two contexts. With respect to covariation of children's vocabulary with mothers'
Context
Covariate(s)a at 13 Months
Predictorat 20 Months
Context
Covariate(s)a at 13 Months
Predictor at 20 Months
**p ~ .01
lOne outlier excluded: n = 29.
~Two outliers excluded: n = 28.
aCovariate(s) entered in separate, ordered steps prior to predictor.
D. Concurrent Correspondenceof Mother Verbal Responseswith Child Vocabulary at 20 Months
Verbal Responses
Play 1. Mother Verbal Responses
3. Child Vocabulary
2. Child Vocabulary
Mealtime 1. Mother Verbal Responses
3. Child Vocabulary
2. Child Vocabulary
C. Concurrent Correspondenceof Mother Vocabulary with Child Vocabulary at 20 Months
Vocabulary
Play1 1. Mother Vocabulary
3. Child Vocabulary
2. Child Vocabulary
Mealtime 1. Mother Vocabulary
3. Child Vocabulary
2. Child Vocabulary
Mother Measure at
20 Months
B. Concurrent Correspondenceof Child Vocabulary with Mother Verbal Responsesat 20 Months
Vocabulary
Play2 1. Child Vocabulary
3. Mother Verbal Responses
2. Mother Verbal Responses
Mealtime 1. Child Vocabulary
3. Mother Verbal Responses
2. Mother Verbal Responses
A. Concurrent Correspondenceof Child Vocabulary with Mother Vocabulary at 20 Months
Vocabulary
Play 1. Child Vocabulary
3. Mother Vocabulary
2. Mother Vocabulary
Mealtime1 1. Child Vocabulary
3. Mother Vocabulary
2. Mother Vocabulary
Child MeaSureat
20 Months
.12
.22
.51
.00
.07
.43
.00
.06
R2 Change
.21
.48
~
.13
.00
.08
.54
.01
R2 Change
.09
~
TABLE 5
Concurrent Correspondences of Child with Mother Language at 20 Months
8.84**
F(1,26) = 8.52**
F(1,26) =
F(1,26) = .14
F(1,25) = .09
F Change
F(1,26) = 8.52**
F(1,24) = 8.18"*
F(1,25) = .18
F(1,26) = .26
F Change
IJI
ixa
5"
I. Child Vocabulary at 13 Months
I. Child Vocabulary at 13 Months
Change
Consistency
I. Child Vocabulary at 13 Months
I. Child Vocabulary at 13 Months
Change
Consistency
Consistency
I. Child Vocabulary at 13 Months
I. Child Vocabulary at 13 Months
Mealtime Average
I. Child Vocabulary at 13 Months
Change
B. Prediction of Child Vocabulary from Mother Verbal Responses from 13 to 20 Months
1. Child Vocabulary at 13 Months
Vocabulary
Play 2 Average
I. Child Vocabulary at 13 Months
I. Child Vocabulary at 13 Months
Consistency
Mealtime Average
I. Child Vocabulary at 13 Months
Change
Child Measure
at 20 Months Context
Model
Covariate(s)a at 13 Months
A_Prediction of Child Vocabulary from Mother Vocabulary from 13'"to 20 Months
1. Child Vocabulary at 13 Months
Vocabulary
Play
Average
.04
.05
.18
.00
.23
.45
-.05
.13
.21
.02
-.07
.13
.00
.20
.46
.04
-.21
.10
.04
-.06
.34
.00
.21
2. Mother Average Vocabulary at 13 &
20 Months
2. Change in Mother Vocabulary at 13
& 20 Months
2. Consistency in Mother Vocabulary at
13 & 20 Months
2. Mother Average Vocabulary at 13 &
20 Months
2. Change in Mother Vocabulary at 13
& 20 Months
2. Consistency in Mother Vocabulary at
13 & 20 Months
2. Mother Average Verbal Responses at
13 & 20 Months
2. Change in Mother Verbal Responses
at 13 & 20 Months
2. Consistency in Mother Verbal
Responses at 13 & 20 Months
2. Mother Average Verbal Responses at
13 & 20 Months
2. Change in Mother Verbal Responses
at 13 & 20 Months
2. Consistency in Mother Verbal
Responses at 13 & 20 Months
.04
~
Predictor
R2 Change
TABLE 6
Predictive Validity of Child and M o t h e r Language from 13 to 20 Months: Comparisons among Three Models
F(1,27) = .07
~D
~o
.-L
z
9
Na
<
o
F(1,27) = 7.35*
z
I71
©
<
<>
"1-
z
--4
F(1,27) = 1.64
F(1,25) = 2.10
F(1,25) = 7.70**
F(1,25) = 5.43*
F(1,26) = .59
F(1,26) = .14
F(1,26) = 1.59
F(1,27) = 1.72
F(1,27) = .12
F(1,27) = 1.79
F Change
1. Mother Vocabulary at 13 Months
Consistency
1. Mother Verbal Res oonses at 13 Months
1. Mother Verbal Res oonses at 13 Months
Change
Consistency
1One outlier excluded: n = 29.
2Two outliers excluded: n = 28.
aCovariate(s) entered in separate, ordered steps prior to prediction.
**p ~ ,01; ***p ~ .001
1. Mother Verbal Res oonses at 13 Months
1. Mother Verbal Res ~onses at 13 Months
Mealtime Average
Consistency
D. Prediction of Mother Verbal Responses from Child Vocabulary
Verbal
Play
Average
1. Mother Verbal Res ~onses at 13 Months
Responses
1. Mother Verbal Res ~onses at 13 Months
Change
1. Mother Vocabulary at 13 Months
1. Mother Vocabulary at 13 Months
Consistency
Change
1. Mother Vocabulary at 13 Months
Change
1. Mother Vocabulary at 13 Months
Play1
Vocabulary
Covariate(s)a at
Predictor at 20 Months
13 Months
1. Mother Vocabulary at 13 Months
Average
Mealtime Average
Context
Mother
Measure at
20 Months
2. Child Average Vocabulary at 13 & 20
Months
2. Change in Child Vocabulary at 13 &
20 Months
2. Consistency in Child Vocabulary at
13 & 20 Months
2. Child Average Vocabulary at 13 & 20
Months
2. Change in Child Vocabulary at 13 &
20 Months
2. Consistency in Child Vocabulary at
13 & 20 Months
2. Child Average Vocabulary at 13 & 20
Months
2. Change in Child Vocabulary at 13 &
20 Months
2. Consistency in Child Vocabulary at
13 & 20 Months
2. Child Average Vocabulary at 13 & 20
Months
2. Change in Child Vocabulary at 13 &
20 Months
2. Consistency in Child Vocabulary at
13 & 20 Months
.02
.01
.27
.00
.12
.54
-.04
.04
.21
.14
.04
.19
.23
.03
-.19 .
.48
.10
.32
.01
.01
.09
-.09
.04
-.20
R2 Change F Change
=
1.44
F(1,27) = .06
F(1,27) = 11.79**
F(1,27) = .4O
F(1,27) = .85
F(1,27) = 17.06***
F(1,27) = .25
F(1,27) = 1.57
F(1,27) = 1.21
F(1,27) = 1.19
F(1,26) = 4.05
F(1,26) = .24
F(1,26)
5'
78
INFANT BEHAVIOR & DEVELOPMENT
verbal responses, however, all relations were
significant, .42 < rs(28) < .65, ps < .01.
Table 5 shows the results of hierarchical
multiple regression analyses that examined
unique simultaneous relations at 20 months
between children and their mothers. For example, in the model developed to estimate the
relation between mothers' vocabulary at 20
months with children's vocabulary at 20
months in a single context (Table 5A), children's vocabulary at 13 months, mothers'
vocabulary at 13 months, and mothers' vocabulary at 20 months were entered in ordered
sequential steps. Unique prediction of child
20-month vocabulary by mother 20- month
vocabulary was again examined by evaluation
of the R 2 change associated with mothers'
vocabulary at 20 months controlling for the
13-month child and mother covariates. Table
5A shows that mothers' vocabulary at 20
months did not uniquely predict children's
vocabulary at 20 months at play or in mealtimes. Table 5B shows, by contrast, that mothers' verbal responses at 20 months uniquely
predicted children's vocabulary at play and in
mealtimes at 20 months controlling for child's
vocabulary at 13 months and mothers' verbal
responses at 13 months. Notably, these relations held in follow-up analyses controlling for
total maternal utterances: In play, fl = .79, R2
change = .18, F(1,23) = 13.01,p < .001, and at
mealtimes, fl = .51, R 2 change = .17,
F(1,25) = 6.88,p < .02.
Tables 5C and 5D show the reciprocal concurrent relations of mothers with their children. Children's vocabulary at 20 months did
not uniquely predict their mothers' vocabulary
at 20 months (Table 5C). However, children's
vocabulary at 20 months uniquely predicted
their mother's verbal responses in both contexts at 20 months (Table 5D). In follow-up
analyses, which controlled for children's total
utterances, these two relations attenuated to
nonsignificance--in play, fl = .27, R 2
change = .02, F(1,25) = 1.93, ns, and at mealtimes, fl = .29, R 2 change = .05, F(1,25) = 2.19,
ns--on account of high positive correlation, r
.90, between the two predictors.
Vol. 22, No. 1, 1999
Predictive Validity o f Child a n d
M o t h e r Vocabulary and Verbal
Responsiveness
Finally, we examined predictive relations
between child and mother, and mother and
child, for each of the language measures in
each of the contexts. At the zero order level,
only one of the eight predictive relations, mean
Irl = .17, was significant: In play, mothers'
responsiveness at 13 months predicted child
vocabulary at 20 months, r(26) = .59,p < .001.
However, lag relations as indexed by simple correlations include variation that may be
accounted for by stability within a person as
well as by the influence of the partner interactant/conversant. Therefore, for language
assessed at 20 months in each context, separate
hierarchical regression analyses that modeled
one of three lagged predictive processes were
conducted to evaluate whether variation in
partner A at 13 months predicted variation in
partner B at 20 months when controlling for
the consistency in partner B from 13 to 20
months. These models differed in the predictors that were used to describe effects of one
partner in the dyad on the other taking into
account both earlier and later time periods.
In the developmental average model, mothers' average vocabulary across the two ages,
computed as the mean of the sum of their standardized scores at 13 months and 20 months,
was used to predict children's vocabulary at 20
months after controlling for the children's
vocabulary at 13 months. For example, in
Table 6A, the developmental average model
tested the prediction of children's vocabulary
at 20 months by mothers' average vocabulary
between 13 and 20 months, over and above
children's vocabulary at 13 months, all in the
same context: Children's vocabulary at 13
months and the average of their mothers'
vocabulary at 13 and 20 months were entered
in that order as predictors in hierarchical
regression equations, and unique predictive
relations associated with mothers' average
vocabulary were examined by evaluation of
the standardized regression coefficient,/~, and
Child Languagein Year2
the increment in the squared multiple correlation, R2 change. In the developmental change
model, mothers' developmental increase (or
decrease) in vocabulary, computed as the difference of their standardized score at 20
months less their standardized score at 13
months, was used to predict children's vocabulary at 20 months again controlling for children's vocabulary at 13 months. In the
developmental consistency model, mothers'
consistency in vocabulary across the two ages
was computed as 1 less the absolute difference
of their standardized scores at 13 and 20
months divided by the maximum absolute
standardized score at either 13 or 20 months;
for each measure, this procedure yielded
scores ranging from 0 (no consistency) to 1
(total consistency). This consistency measure
was used to predict children's vocabulary at 20
months after controlling for children's vocabulary at 13 months. Analogous models were
tested with mothers' verbal responsiveness as
the predictor of child vocabulary, with child
vocabulary as the predictor of mother vocabulary, and with child vocabulary as the predictor
of mothers' verbal responsiveness.
Two main findings emerged from this
series of regressions: (1) models involving
maternal verbal responsiveness outweighed
models involving maternal vocabulary in significance; and (2) change models of developmental increase were the most pervasive and
powerful of the three developmental models in
both mothers and children, with the average
model next most important and the consistency
model least influential.
Mother-to-Child Predictions
No significant predictive relations from
maternal vocabulary in the two contexts
emerged for predicting child vocabulary for
the developmental average, change, or consistency models (Table 6A). All effect sizes (R2
change) were small (.00 to .04), and so it is
unlikely that the power to detect sizeable
effects is at issue. By contrast, increases in
mothers' verbal responses between 13 and 20
79
months (positive fl in the developmental
change model) uniquely predicted children's
vocabulary at 20 months in both contexts
(Table 6B). Average maternal responsiveness
in play between 13 and 20 months also predicted children's vocabulary at 20 months.
Child-to-Mother Predictions
No significant predictive relations from
child vocabulary in the two contexts emerged
for predicting mother vocabulary for the developmental average, change, or consistency
models (Table 6C). All effect sizes (R2
change) were small (.01 to .10), and so it is
again unlikely that the power to detect sizeable
effects is at issue. By contrast, again, increases
in children's vocabulary between 13 and 20
months (the developmental change model)
uniquely predicted mothers' verbal responses
at 20 months in both contexts (Table 6D).
DISCUSSION
This study examined mutual influences of
child and mother language in spontaneous
speech in different contexts across the second
year. We compared productive vocabulary in
mother-child conversations with maternal verbal responses to children's speech in order to
encompass noteworthy social-interactional
influences on child language. In a larger-scale
normative study, Fenson, Dale, Reznick,
Bates, Thai, and Pethick (1994) reported substantial variability in vocabulary in children
between 8 and 30 months of age, and sources
of individual variation in vocabulary acquisition have been a subject of continuing interest
(Bates et al., 1995; L. Bloom, 1993; Bornstein,
Haynes, & Painter, 1998; Goldfield &
Reznick, 1990; Mervis & Bertrand, 1995).
Certainly, there is perennial interest in relations between parenting processes and child
language development. Children bring native
abilities as well as inductive cognitions to
acquiring vocabulary, but they are also
exposed to language input and they are sup-
80
INFANT BEHAVIOR & DEVELOPMENT Vol. 22, No. 1, 1999
ported by language experiences. This study
focused on the processes and effects of variation in two domains of language experience for
children's vocabulary acquisition. Our findings indicate that children's productive vocabulary reflects in part their differential
experiences and in part individual differences
in children themselves.
Both children and their mothers showed
group mean level changes in productive
vocabulary as children grew across the second
year. In this age period, children displayed a
nearly 14-fold increase in word roots used at
play and more than a 7-fold increase in word
roots used in mealtimes. As to changes in
mothers, presumably they did not acquire new
vocabulary in this same 7-month period, but
rather used more of their vocabulary with their
children as their children aged. This finding
accords with a language literature on "child
effects;" mothers appear to tailor their linguistic sophistication to meet their children's
growing language abilities (see Bellinger,
1980; Bohannon & Marquis, 1977; Huttenlocher et al., 1991; McLaughlin, White,
McDevitt, & Raskin, 1983). Similarly, crosscultural data show that mothers in Argentina,
France, Japan, and the U.S. all increase in their
language use to children between 5 and 13
months (Bornstein et al., 1992). Context
effects in children's vocabulary in spontaneous speech were also in evidence, such that
older children used more words at play than in
mealtimes (see, too, Weismer, MurrayBranch, & Miller, 1994). Because of obvious
task constraints, children may use less vocabulary when eating than when at play. Mothers
also used more vocabulary at play, perhaps
because meals are "event stereotyped" or
because play situations promote language use
as a supplementary didactic tool. At a minimum, these context effects have methodological implications for where and when child
language is evaluated; in addition, the revelation of these kinds of context effects has potential implications for where and when motherchild language will assume divergent characteristics.
The extent to which variation in language
represents a consistent attribute in the individual was addressed by examining stability (an
individual differences construct) across both
age and context. Children showed moderateto-strong stability in their spontaneous productive vocabulary both within context across age
and within age across context; indeed, we
observed stability in child vocabulary even
when we statistically controlled maternal
vocabulary and verbal responses. These data
articulate with previous reports, based on
maternal estimates, that individual variation in
productive vocabulary in young children is stable (e.g., Bates et al., 1995; L. Bloom, 1993;
Tamis-LeMonda & Bornstein, 1994). Maternal vocabulary and verbal responses were also
highly stable across the child's second year
and across contexts, even when we partialled
potential influences of child vocabulary. Even
so, the present cross-contextual design may
underestimate true stability in child and
mother vocabulary and in maternal verbal
responses in that children and their mothers
would be expected to show greater short-term
stability when observed twice in the same situation on the same day (say, twice at play) than
when observed in different situations (once at
play and once in a meal) as examined here.
Concurrent relations between child and
maternal vocabulary measures at 20 months
were not significant, whereas concurrent relations between children's vocabulary and
maternal verbal responses were stronger.
Expectedly, then, children with more vocabulary had mothers who were more verbally
responsive at 20 months. Other investigators
have also uncovered concurrent relations
between mother-child interactions and verbal
achievements in 18- to 24-month children
(e.g., Olson, Bates, & Bayles, 1984).
Specific mother-to-child and child-tomother lagged relations emerged that identified two key features of predictive relations:
first, specificity in the domain of language
development; and, second, the importance of
responsiveness in parenting. Maternal verbal
responsiveness to children was more predic-
Child Language in Year 2
tive of child vocabulary than was maternal
vocabulary per se. In a specificity view, child
characteristics and environmental influences
are each best characterized as multidimensional. In child development, general environmental stimulation or experiences do not
influence general ability globally (see Maccoby & Martin, 1983), so much as specific
forms of environmental stimulation or experience influence specific abilities in specific
ways (Bornstein, 1989b, 1995; Wachs, 1992).
The main effects we found in child-mother
language exchange reflected such specific
associations and pathways: Notably, maternal
verbal responsiveness, rather than maternal
vocabulary, predicted child vocabulary. This
does not mean, of course, that vocabulary is
unimportant (e.g., Huttenlocher et al., 1991);
the vocabulary to which the young child is
exposed is responsive and nonresponsive, and
future research might compare the numbers of
different words in response and nonresponse.
Moreover, features of maternal speech other
than verbal responsiveness and supplementary
to vocabulary, such as talkativeness, pragmatic
relevance, total maternal speech, and the like,
could also predict child vocabulary. For example, Hart and Risley (1992) found that parents'
use of modifiers, past-tense verbs, and fewer
imperatives predicted the amount and variety
of vocabulary their children used at 3 years.
Complementarily, caregiver vocabulary could
predict other features of child language: We
studied expressive vocabulary, but in this age
range rapid increases in receptive vocabulary
occur developmentally earlier. Perhaps maternal expressive vocabulary would relate to
increases in comprehension.
Maternal verbal responsiveness to children
was more predictive of child vocabulary than
was maternal vocabulary per se, so responsiveness proved significant. Others have previously found predictive associations between
maternal responses and child language performance (e.g., Baumwell et al., 1997; K. Bloom,
1979; L. Bloom et al., 1996; Bornstein &
Tamis-LeMonda, 1989; Hoff-Ginsberg &
Shatz, 1982; Olson, Bayles, & Bates, 1986;
81
Tamis-LeMonda, Bomstein, Kahana-Kalman,
Baumwell, & Cyphers, 1998). Importantly,
contingent maternal verbal responses to the
vocalizations of adopted 1-year-olds predict
their communicative development, thereby
isolating the validity of responsiveness per se
from any potential shared genetic variance
(e.g., Hardy-Brown et al., 1981). Such findings
support the meaningfulness and validity of this
particular social-interactional pattern to child
language acquisition, and the results of our
contrast articulate well with contemporary theoretical models of the young child's transition
to language (see L. Bloom, 1993) that stress
the relevance of the language the child hears to
what the child has in mind for word learning
(e.g., Baldwin, 1991; Bornstein, 1985; Tomasello et al., 1986). This pattern of findings also
has clear intervention applications.
We analyzed absolute levels of maternal
responses in this study. It would also be possible to evaluate sequences of verbal exchanges
between mother and child, the effectiveness of
relative maternal responsiveness, or nonverbal
or physiological responses of mothers to capture other ways in which children's verbal
behaviors might be effectively followed by
maternal response. The volume of maternal
responses is a demonstrably meaningful aspect
of mother-child verbal interaction, and the
measure we chose of the frequency of maternal
responses is comparable to measures of the
frequency of vocabulary. Furthermore, the
analytic models brought to bear on these data
adjust for aspects of child behavior--notably
child vocabulary--in evaluating the effects of
maternal responsiveness.
Just how and why verbal responses are
influential constitute additional, but separate,
questions meritorious of independent investigation. On a joint attention explanation, for
example, verbally responsive mothers might
normally monitor their children's visual attention and activity closely and then respond contingently, thereby maximizing children's
matching words or phrases with targets of their
current attentional focus (see Baldwin, 1991;
Bornstein, 1985; Dunham & Dunham, 1995).
82
INFANT BEHAVIOR & DEVELOPMENT Vol. 22, No. 1, 1999
Pragmatically, verbal responsiveness, which
continues the child's topic or focus of activity,
might be viewed also as offering an opportunity for more activation of already acquired
vocabulary, either through the child's continuing attention to the activity or through priming
of relevant vocabulary. These effects in turn
might act to increase access to already
acquired vocabulary; the same contexts, of
course, also permit the rapid (perhaps onetrial) learning of new vocabulary in comprehension, and again might constitute more
effective contexts than nonverbally responsive
ones because the child's attention is already
appropriately engaged. More generally,
responsive mothers might also be more sensitive to the developmental needs of their children, more knowledgeable about child
development, or simply change appropriately
in their activities to keep apace of their developing children's changing needs, and thereby
also influence their children's language development (e.g., Bornstein, Haynes, & Painter,
1998; Damast, Tamis-LeMonda, & Bornstein,
1996; Pederson, Moran, Sitko, Campbell,
Ghesquire, & Acton, 1990). Caregivers who
verbally label around their children's focus of
attention or gesturing, and caregivers who imitate, expand upon, and otherwise verbally
respond to their children's attempts at language mastery, might encourage advances in
language directly by easing the task of symbolreferent matching, or they may do so indirectly
by inculcating in their children general feelings of self-efficacy, control, and competence
(see Baumwell et al., 1997; Bornstein, 1985;
Hardy-Brown et al., 1981; Hoff-Ginsberg &
Shatz, 1982; Olson, Bates, & Bayles, 1984;
van Ijzendoorn et al., 1995).
Finally, of several possible models of
unique predictive relations, change models of
maternal verbal responsiveness showed stronger predictive power than average or consistency models. Aggregating over the three main
results, it is noteworthy that developmental
increases in maternal verbal responses constituted the specific and most potent predictive
combination in promoting children's produc-
tive vocabulary in spontaneous speech. Generally speaking, then, semantic and syntactic
modifications in parental speech that are
dynamically sensitive, in the sense of matching children's developing linguistic competencies, appear to be the most effective in
promoting children's language growth. Parents
who create and maintain responsive vocal
environments support their verbally developing young children.
Acknowledgments:
We thank J. Genevro
and B. Wright for comments and assistance.
Requests for reprints should be sent to Marc
H. Bornstein, Child and Family Research,
National Institute of Child Health and Human
Development, National Institutes of Health,
Building 31--Room B2B15, 9000 Rockville
Pike, Bethesda MD 20892-2030, U.S.A.
Email: Marc_H [email protected].
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05 January 1998; Revised 27 September 1998 •