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Children's Vocabulary Growth in Englishand Spanish Across Early Developmentand Associations With School ReadinessSkillsCatherine S. Tamis-LeMonda a , Lulu Song b , Rufan Luo a , YanaKuchirko a , Ronit Kahana-Kalman c , Hirokazu Yoshikawa a & JuliaRaufman aa Department of Applied Psychology , New York University , NewYork , New Yorkb Early Childhood Education, Brooklyn College , New York , New Yorkc NYU Center for Research on Culture, Development and Education ,New York , New YorkPublished online: 26 Feb 2014.

To cite this article: Catherine S. Tamis-LeMonda , Lulu Song , Rufan Luo , Yana Kuchirko , RonitKahana-Kalman , Hirokazu Yoshikawa & Julia Raufman (2014) Children's Vocabulary Growth in Englishand Spanish Across Early Development and Associations With School Readiness Skills, DevelopmentalNeuropsychology, 39:2, 69-87, DOI: 10.1080/87565641.2013.827198

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DEVELOPMENTAL NEUROPSYCHOLOGY, 39(2), 69–87Copyright © 2014 Taylor & Francis Group, LLCISSN: 8756-5641 print / 1532-6942 onlineDOI: 10.1080/87565641.2013.827198

Children’s Vocabulary Growth in English and SpanishAcross Early Development and Associations With School

Readiness Skills

Catherine S. Tamis-LeMondaDepartment of Applied Psychology, New York University, New York, New York

Lulu SongEarly Childhood Education, Brooklyn College, New York, New York

Rufan Luo and Yana KuchirkoDepartment of Applied Psychology, New York University, New York, New York

Ronit Kahana-KalmanNYU Center for Research on Culture, Development and Education, New York, New York

Hirokazu Yoshikawa and Julia RaufmanDepartment of Applied Psychology, New York University, New York, New York

In line with evidence that variation in children’s vocabulary size facilitates learning, we askedwhether growth in Mexican and Dominican children’s expressive vocabularies in English and/orSpanish would predict later cognitive skills. Children and mothers were video-recorded sharingwordless books at 2, 3, 4, and 5 years, and children were assessed on language, literacy, and mathskills at 5 years. Growth in children’s English and Spanish vocabularies, based on transcriptionsof booksharing interactions, predicted specific cognitive skills and was associated with changes tomothers’ language use across time. Mothers’ years in the United States predicted children’s Englishvocabulary growth.

In this longitudinal investigation, we examine the correlates and developmental consequencesof English and Spanish vocabulary growth in Latino children from Dominican and Mexicanbackgrounds. Children’s early growth in vocabulary is foundational to cognitive developmentand school readiness as words represent an interconnected, hierarchical web of knowledge.Children with larger vocabularies in infancy and toddlerhood show an advantage in processingspeed (Marchman, Fernald, & Hurtado, 2010; Tamis-LeMonda & Bornstein, 1989) compared to

Correspondence should be addressed to Catherine S. Tamis-LeMonda, Department of Applied Psychology, New YorkUniversity, 246 Greene street, 410W, New York, NY 10003. E-mail: catherine.tamis-lemonda@nyu.edu

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children with smaller vocabularies. Individual differences in vocabulary size are also stable overtime: Already by 1 to 2 years of age, children’s vocabulary size predicts later vocabulary sizeand growth (Fenson et al., 1994), reading achievement (Marchman & Fernald, 2008), grammati-cal development (Bates & Goodman, 1999; Marchman, Martínez-Sussmann, & Dale, 2004), and8-year cognitive skills, including working memory and IQ (Marchman & Fernald, 2008).

However, most research on the developmental sequelae of early language developmentis based on children reared in monolingual contexts, resulting in a knowledge base that ispractically and theoretically limited. At a practical level, research on monolingual languagedevelopment excludes a substantial portion of the population from basic developmental research.Approximately half of the world’s children live in bilingual homes or communities (Grosjean,2010) and approximately one-fourth of U.S. children live in immigrant households with parentswho speak a language other than English (Hernandez, Denton, & Macartney, 2008). At a the-oretical level, little is known about how children come to navigate two language systems andwhether skills within and/or across languages support later developing cognitive skills. Childrenexposed to two or more languages must learn distinct rules for mapping experiences to words(lexical development), combining words into sentences (grammatical development), and usinglanguage in culturally acceptable ways (pragmatic development). Consequently, the heterogene-ity seen among children exposed to two or more languages is striking, with individual childrenvarying in their rates of growth and levels of attainment in each (Place & Hoff, 2011; Song, Tamis-LeMonda, Yoshikawa, Kahana-Kalman, & Wu, 2012). Here, we prospectively examine variationin children’s vocabulary growth—in Spanish and English—in relation to language, literacy, andmath skills at age 5 years.

VOCABULARY DEVELOPMENT AND COGNITIVE SKILLS

Why might variability in early vocabulary growth predict children’s later cognitive skills?Neuropsychological research provides a useful framework for explaining developmental stabili-ties in language and cognition: biological constraints interact with environmental inputs (notably,parental language) in the early emergence of an efficient cortical network for language process-ing (Dehaene-Lambertz et al., 2010), which in turn facilitates the learning of new information.More specifically, structural asymmetry of the brain functions to support a left-hemisphereadvantage for the channeling of speech. This channeling results in changed neural response,improved perception of meaningful phonemes, and in turn, more efficient processing of newwords (Dehaene-Lambertz et al., 2010).

Studies of N400 priming effects provide especially compelling evidence for the reciprocalassociations among vocabulary growth, neural response, and learning. In one study, the languageskills of 12-month-olds (reported by parents) were examined in relation to event-related poten-tials (ERPs) during a picture-word priming paradigm. Infants with high early word productiondisplayed an N400 semantic priming effect whereas infants with low early word production didnot (Friedrich & Friederici, 2010). Because the N400 priming effect is thought to reflect facil-itated access to word meanings, these findings have implications for infants’ learning of novelwords and concepts. For example, when infants confront words that contain partially overlappingmeanings (e.g., cat, dog), the learning of the “new” word (e.g., cat) is facilitated when thesemantic representation of the familiar word (e.g., dog) is “sufficiently specified” (Friedrich &

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DUAL LANGUAGE DEVELOPMENT 71

Friederici, 2010) or “richly instantiated” (Dapretto & Bjork, 2000). Mechanisms underlying theN400 elicitation may also be directly involved in inhibitory processes that aid word learning.If incoming information activates several possible semantic representations, the N400 componentof the ERP might suppress activity patterns associated with inaccurate representations (Friedrich& Friederici, 2010).

As such, a growing vocabulary is simultaneously the result of and catalyst for learning. Indeed,vocabulary is considered to be a core aspect of general intelligence (Bates & Goodman, 1999),and predicts children’s performance on standardized intelligence and cognitive tests. In onelongitudinal study of monolingual children, 2-year vocabulary size predicted children’s laterexpressive language, skills at formulating and recalling sentences, working memory, and a generalindex of intelligence based on spatial reasoning, pattern matching, learning, and problem solv-ing (Marchman & Fernald, 2008). This suggests that if rich language networks facilitate furtherlearning, growth in either English or Spanish should cascade to later cognitive skills since con-ceptual representations of a word are roughly the same in either language (Patterson & Pearson,2004). In one study of bilingual infants, processing speed in each language was associated with acomposite measure of vocabulary (i.e., based on Spanish and English; Marchman et al., 2010).

THE SOCIOCULTURAL CONTEXT OF CHILD VOCABULARY DEVELOPMENT

Children do not acquire language in a vacuum. Rather, vocabulary development is the productof social interactions in which children are continually exposed to new words and associatedconcepts. These proximal experiences are nested within a broader ecological context, which fordual-language learning children includes factors that might affect their parents’ language to them,such as parents’ education or years in the United States (Song et al., 2012). An ancillary aim,therefore, was to consider children’s vocabulary growth (in English and Spanish) in relation totheir proximal language experiences and the broader social context.

At the proximal level, we focus on mothers’ use of Spanish and English with children.Research with monolingual samples indicates that children exposed to more frequent, diverse,and responsive language have larger vocabularies and/or achieve language milestones sooner indevelopment than those exposed to language that is relatively impoverished (Hart & Risley, 1995;Huttenlocher, Haight, Bryk, Seltzer, & Lyons, 1991; Tamis-LeMonda, Bornstein, & Baumwell,2001). Moreover, children’s home language experiences explain socioeconomic disparities inchildren’s language and cognitive performance (Hart & Risley, 1995; Rowe, 2008). The predic-tive validity of maternal language has been generalized to monolingual Spanish-language learnersfrom low-income Latino families (Hurtado, Marchman, & Fernald, 2008): The amount motherstalked to their 18-month-olds during free play predicted children’s productive vocabularies andskills at recognizing familiar words at 2 years.

The importance of maternal talk for bilingual children’s language and cognitive developmenthas also been documented (Jia, Aaronson, & Wu, 2002; Song et al., 2012; Tamis-LeMonda,Song, Leavell, Kahana-Kalman, & Yoshikawa, 2012), and is further supported by brain research.Bilinguals exposed to a second language prior to age 5 years have greater tissue density in brainareas related to language, memory, and attention than those exposed to a second language laterin development (Mechelli et al., 2004). In one study, bilingual infants were assessed on: (1) theirexposure to Spanish and English in the home, (2) neural indicators (i.e., ERPs) of phonetic

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discrimination of Spanish and English, and (3) their later bilingual word production abilities.Infants’ exposure to each of the languages was associated with their early neural discriminationskills, and both language exposure and phonetic discrimination predicted later word production(Garcia-Sierra et al., 2011).

In terms of contextual factors, children’s exposure to English and Spanish is likely to beaffected by mothers’ years in United States and years of education, both of which vary acrosssub-groups of the Latino population. However, investigators often take a pan-ethnic approachto the study of Latinos, which obscures individual differences in Latinos from different ethnic-ities (Song et al., 2012). For example, toddlers from Mexican versus Dominican backgrounds(the groups studied here) display dramatic within- and between-group variability in their Englishand Spanish receptive and productive vocabularies, communicative gestures, and vocalizationsto mothers during play; these group and individual differences are at least in part explained bydifferences in mothers’ backgrounds and in turn communications with infants (Song et al., 2012;Tamis-LeMonda et al., 2012). Mexicans are a recent Latino immigrant group to the NortheastUnited States (the location of the current study), mostly first generation, with relatively lowlevels of education, and few years of education completed in the United States (Smith, 2006).Dominicans have a longer history in the Northeast than Mexicans and have higher proportions ofmulti-generational households than Mexican immigrants. As parents reside in the United Statesfor longer periods, they increasingly adopt the language and customs of the host society, and like-wise change in their parenting views and practices (Cabrera, Shannon, West, & Brooks-Gunn,2006). In turn, differences in parents’ backgrounds affect children through influences on proxi-mal processes, such as parents’ relative use of English or Spanish during language and literacyinteractions (Song et al., 2012).

Finally, we examine children’s gender in analyses. There is evidence that girls have a slightlanguage advantage relative to boys as assessed across a variety of data types, including maternalreport, spontaneous production, and standardized assessments (e.g., Bornstein & Haynes, 1998;Fenson et al., 1994; Huttenlocher et al., 1991; Morisset, Barnard, & Booth, 1995). However,the female advantage is small and short-lived, and a study of language skills of toddlers fromlow-income families failed to find any gender differences (Pan, Rowe, Spier, & Tamis-LeMonda,2004).

CURRENT STUDY

To summarize, we asked whether children’s vocabulary growth from 2 to 5 years in Englishand/or Spanish predicts three aspects of school readiness at age 5 years: expressive vocabulary,emergent literacy, and emergent math. These skills are building blocks for school readiness andlater academic achievement. Based on the premise that children with large vocabularies havericher conceptual networks than those with smaller vocabularies, we expected predictive patternsto generalize across the two languages. Additionally, we asked whether mothers’ English andSpanish language use predicts variability in children’s vocabulary growth. Changes in mothers’English and Spanish language use with children were expected to relate to growth in children’svocabulary in the respective languages. We also considered the role of the broader ecologicalcontext in models, asking whether mothers’ ethnicity, years in the United States, and educa-tion might relate to mothers’ amount and/or relative use of English and Spanish and in turn

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DUAL LANGUAGE DEVELOPMENT 73

children’s vocabulary growth. Finally, we expected girls to be at an advantage relative to boys,and to perhaps show faster growth in language over time. A dynamic and comprehensive accountof the vocabulary development of dual-language learning children requires attention to children’svocabulary skills in both English and Spanish at multiple times in early development (Patterson& Pearson, 2004).

METHODS

Participants

Participants were 133 Dominican (n = 64) and Mexican (n = 69) immigrant mothers and theirchildren (balanced for gender). Mothers who self-identified as being born in Mexico or theDominican Republic were recruited from hospital maternity wards shortly after giving birth tothe focal child. Inclusionary criteria were mothers being at least 18 years of age, residing in alarge northeastern U.S. city (excluding shelters), and infants being healthy and full term at birth.The 133 mother-child pairs represented 73% of the original hospital-recruited sample of firstgeneration Mexican and Dominican participants. The remaining 27% of families were lost dueto moves (n = 2), voluntarily dropping from the study (n = 7), or loss of contact (e.g., discon-nected phones; inaccurate contact information) (n = 42). At child birth, mothers ranged from18 to 41 years (M = 27.17 years, SD = 5.31). Dominican mothers had more years of educa-tion than did Mexican mothers (Ms = 12.24 and 8.19, respectively), t(128) = 8.13, p < .001.Dominican mothers also lived in the United States for more years than did Mexican mothers(Ms = 9.73 and 7.74, respectively), t(122) = 1.94, p = .055. Given the differences on these vari-ables between the Latino groups and the potential effect they have on children’s dual languageexperience, these contextual factors were included in all analyses.

Procedures

Data are based on video-recorded observations of child–mother booksharing when children were2 years (M = 24.49 months, SD = 1.35), 3 years (M = 35.63 months, SD = 1.95), 4 years(M = 49.64 months, SD = 1.56), and 5 years (M = 60.71 months, SD = 1.36) of age; directassessments of children’s cognitive skills at age 5 years (i.e., expressive vocabulary, emergentliteracy, and emergent math); and interviews with mothers that provided demographic informa-tion. Participants were seen in their homes at the 2- and 3-year assessments and in the laboratoryfor the 4- and 5-year assessments. Families received $75 when children were 2 and 3 years and$100 when children were 4 and 5 years as compensation for participation.

Child and mother language. At the 2-year visit, dyads shared a wordless number bookand a wordless emotion book, containing pictures of common objects (e.g., cookies) and infantfaces with different expressions, respectively. At the 3-, 4-, and 5-year assessments, dyads sharedthe wordless book Frog, where are you? by Mercer Mayer. At each age, mothers were askedto “Please share this book with your child as you normally would.” The use of wordless booksensured that mothers did not have to be literate in Spanish or English to share the book with theirchildren.

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We focused on booksharing as both mothers and children vary substantially in the amountand diversity of language they use during these interactions, and variation in mothers’ languageduring booksharing reliably predicts children’s cognitive and language skills (Tamis-LeMondaet al., 2012). As a check on the ecological validity of booksharing, we asked mothers aboutwhether they shared books with their children at home, or if their children were “still too youngfor that.” We used this wording to minimize social desirability of responses. At each of the fourassessments, over 90% of the mothers reported reading books with their children, which alignswith other research indicating that messages about the importance of booksharing has reachedparents of ethnically diverse, low-income backgrounds (Raikes et al., 2006). Finally, to ensurethat estimates of mothers’ language use during booksharing were reliable, we ran a check onthe cross-situational stability of mothers’ language diversity (word types) at the first wave ofassessment (2 years). The diversity of words mothers used during booksharing strongly related tothe diversity of words they used during play (r = .70, p < .001).

Booksharing sessions lasted an average of 3.79 min (SD = 0.35) at the 2-year assessment,5.83 min (SD = 2.12) at 3 years, 6.95 min (SD = 2.60) at 4 years, and 5.25 min (SD = 2.03) at5 years. Given these differences in session duration, measures of mother and child language wereprorated to reflect word usage “per minute” (see below).

Mothers’ and children’s language during booksharing sessions was transcribed from the vide-orecords by bilingual English and Spanish speakers using a standardized format, Codes for theHuman Analysis of Transcripts (CHAT), and analyzed with the assistance of programs availablethrough the Child Language Data Exchange System (CHILDES; MacWhinney, 2000). Number ofword types (number of different words) and tokens (total number of words) for both English andSpanish were generated using the FREQ program within CHILDES for all participants at eachtime point. To obtain separate counts for English and Spanish, bilingual researchers transcribedinteractions verbatim, and then marked each Spanish and English word on transcripts. From thesemarked transcripts, separate documents were created (one with English words only, and one withSpanish words only) and analyzed using FREQ in CHILDES. This approach yielded word typesfor the English subset of words and the Spanish subset of words for each child and each motherat each age.

We further calculated the average number of word types per minute expressed by child andmother in each language at each age. Word types per minute was calculated by dividing the totalnumber of word types (expressed by child/mother) by the duration of the booksharing session(i.e., number of minutes) at that age. Children’s and mothers’ vocabulary growth/change rates inEnglish and Spanish were based on linear slopes for word types per minute across the four ages,estimated using growth curve analyses in STATA (StataCorp, 2011).

Cognitive skills. At the 5-year visit, children were assessed on various cognitive skills.Testing began with the Early One Word Picture Vocabulary Test (Brownell, 2000). This task isbased on the child’s spontaneous labeling of pictures and therefore enabled the examiner to deter-mine the child’s preferred language. For each picture, the examiner pointed and asked “What’sthis?” in Spanish (if mother reported the child spoke primarily Spanish at home) or English (ifmother reported the child spoke primarily English at home). The question was then repeated inthe opposite language to offer the child an opportunity to respond in the language of choice.Upon completion of the EOWPVT, the examiner segued into the other tests using English (if thechild had responded to the EOWPVT primarily with English; 68.3% of children) or Spanish (if

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the child had responded primarily in Spanish; 26.9% of children). A handful of children (4.8%)who shifted between English and Spanish during the EOWPVT were asked questions in bothlanguages. However, all children across all assessments were credited with a correct responseregardless of the language they used to respond. The crediting of child responses in either lan-guage follows procedures for assessing bilingual children’s language development (Parra, Hoff,& Core, 2011); it minimizes the chances of underestimating the skills of children exposed tomultiple languages and it does not unfairly penalize them for knowing something in a languageother than that of testing.

Expressive vocabulary. A standardized final score was derived from children’s total correctresponses (crediting words produced in either language) on the EOWPVT. A standard score of100 is at the 50th percentile.

Emergent literacy. Two measures were used to assess children’s emergent literacy skills.First, the Letter-Word Identification subtest of the Woodcock Johnson III Tests of Achievement(WJ III; Woodcock, Mather, & Wendling, 2001) measures children’s ability to identify lettersand read words. Children were shown letters and words and asked to sound them out. They werenot required to know the meaning of the words to be credited. Children’s correct responses wereadded and converted to an age equivalent score used subsequently for analyses.

Second, children’s narrative skill was assessed through observations of their independent sto-rytelling. The examiner presented the child with the wordless book “Hug” by author Alborough,and asked the child to tell the story—“Can you tell me a story about it?”—after showing the childthe pages of the book. Children’s storytelling was videorecorded, transcribed using CHILDES(MacWhinney, 2000), and then coded for narrative completeness. Coding was based on com-paring the child’s oral narrative to a pre-specified checklist that included 33 storyline elementsspanning the monkey’s search and subsequent reunion with its parent. On each page of the book,the monkey encounters animals in the woods who are hugging their parents, and the monkeydisplays various emotions and behaviors, including sadness, crying, and ultimately joy uponseeing its parent. Children were credited with each event mentioned (e.g., “The monkey seesthe elephants hugging,” “The monkey is crying,” “The monkey is sad.”). Coders were certi-fied after achieving a reliability score of at least .80 with training transcripts. Two bilingualresearchers recoded 20 transcripts for reliability checking. Inter-rater reliability kappas rangedfrom .82–.92 for transcripts within and across languages.

Children expressed 5.23 storyline events (SD = 4.53) on average, with a range of 0 to 17.Because it was possible that children might tell stories that did not “fit” the a priori deter-mined narrative structure of 33 storyline events, we checked narrative scores against children’sword types during the independent storytelling task. These analyses indicated that narrativescores related strongly to word types (r = .75, p < .001). Thus, children with high narrativescores were those who used more diverse words. Conversely, these checks also indicated thatlow narrative scores reflected skeletal stories, rather than children telling elaborate “alternative”stories.

Emergent math. Children’s emergent math skills were assessed with the Applied Problemsand Quantitative Reasoning subtests of the WJ III. The Applied Problems subtest asks the childto analyze and solve math problems. Children must listen to the description of the problem,recognize the procedure to be followed, and perform calculations to arrive at the answer. The

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Quantitative Concepts subtest of the WJ III measures children’s knowledge of math concepts suchas relations (smaller or bigger than), mathematical notations (e.g., recognition of the subtractionand division signs and the decimal point) in addition to their ability to recognize patterns in anumber line (e.g., counting by 2s).

RESULTS

A core aim was to test whether children’s vocabulary growth in English and/or Spanish predictscognitive skills at age 5 years. Linear slopes for children’s word types per minute in each lan-guage (calculated across the four ages), were derived from growth curve analysis using STATA(StataCorp, 2011), with age nested within children. Quadratic slopes were also derived and testedin models, but they were collinear with linear slopes and did not explain unique variance in cog-nitive skills beyond linear slopes; the quadratic term was thus excluded from models. Separateregression analyses were conducted to examine prediction from children’s vocabulary growth(i.e., linear slopes for English and Spanish) to the dependent variables of children’s expressivevocabulary (EOWPVT), emergent literacy (WJ Letter Word and Narrative Skill), and emergentmath (WJ Quantitative Reasoning and Applied Problems). These models also included the prox-imal predictors of mothers’ linear slopes for English and Spanish word types per minute (alsobased on growth curve analysis), as well as child gender, mother ethnicity, mother years in theUnited States, and mother education. As a first step to analyses, we examined the contextual pre-dictors of the linear slopes of children’s vocabulary growth in English and Spanish. Predictorswere mothers’ linear slopes of English and Spanish words per minute, mother ethnicity, motheryears in the United States, and mother education.

Children’s English and Spanish Vocabulary Growth

Children varied substantially in their linear slopes for Spanish and English (see Figures 1a and1b), as did mothers. To test the contextual predictors of children’s vocabulary growth in eachlanguage, we conducted separate regressions with the linear slope in Spanish and the linearslope in English as dependent variables. In both regression models, female status of the childand Dominican status of the mother were entered in Step 1, followed by mothers’ years in theUnited States and years of education in Step 2, and finally the linear slope of mothers’ Spanishor English vocabulary in Step 3.

In Step 1, female status was positively associated with children’s vocabulary growth in Spanish(ß = .21, p = .012), whereas Dominican status was inversely associated (ß = –.29, p = .001) (seeTable 1). However, the negative association between Dominican status and children’s vocabu-lary growth in Spanish attenuated to nonsignificance once we entered in Step 2 mother years inthe United States, which was also inversely related to children’s vocabulary growth in Spanish(ß = –.23, p = .013). Thus, the Mexican (versus Dominican) “advantage” seen in children’sgrowth in Spanish word types per minute was mediated by mothers’ years in the United States(bias corrected confidence intervals yielded by bootstrapping analysis [Hayes, 2009; Preacher &Hayes, 2008]: [–0.25, –0.06]—confidence intervals that do not include zero indicate mediation).In the final Step, and in support of the importance of proximal language experiences for chil-dren’s vocabulary growth, mothers’ linear slope in Spanish predicted children’s linear slope in

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FIGURE 1 (a) Growth in word types in English across four ages inDominican and Mexican children. (b) Growth in word types in Spanishacross four ages in Dominican and Mexican children.

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TABLE 1Summary of Hierarchical Regression Analysis

of Variables Predicting Children’s Vocabulary Growth in Spanish

Children’s Vocabulary Growth in Spanish

Step Variables Step 1 Step 2 Step 3

1 Dominican −.64 (.18), −.29∗∗ −.37 (.22), −.17 −.27 (.22), −.12Female .46 (.18), .21∗ .45 (.18), .20∗ .43 (.17), .20∗

2 Mother Years in the U.S. −.04 (.02), −.23∗∗ −.03 (.02), −.16Mother Years of Education −.04 (.03), −.14 −.05 (.03), −.15

3 Mother Spanish Slope .10 (.04), .20∗� R2 for step 2 or 3 .05∗ .03∗R2 total .13∗∗∗ .19∗∗∗ .22∗∗∗F(df ) 10.008 (2, 130) 7.36 (4, 128) 7.07 (5, 127)

Note. Values are unstandardized B coefficients, standard error of B (in parenthesis), and ß values from the final regressionequation.∗p < .05. ∗∗p < .01. ∗∗∗p < .001.

Spanish above the other covariates (ß = .20, p = .027). Female status retained its significance.Mothers’ years in the United States attenuated to nonsignificance, indicating that the relationbetween mothers’ years in the United States and children’s Spanish growth was mediated bymothers’ linear slope in Spanish (bias corrected confidence intervals: [–0.03, –0.01]). The overallmodel was significant, F(5, 127) = 7.07, p< .001, and accounted for 22% of the variance.

In the model testing prediction to children’s linear slopes in English (see Table 2), Dominicanstatus predicted in Step 1, indicating more growth in English in Dominican versus Mexicanchildren (ß = .39, p < .001). In Step 2, mothers’ years in the United States predicted (ß = .37,p < .001), and Dominican status retained its significance, although the magnitude of effect was

TABLE 2Summary of Hierarchical Regression Analysis

of Variables Predicting Children’s Vocabulary Growth in English

Children’s Vocabulary Growth in English

Step Variables Step 1 Step 2 Step 3

1 Dominican 1.42 (.29), .39∗∗∗ .84 (.34), .23∗ .65 (.34), .18Female .08 (.29), .02 .12 (.27), .03 .21 (.26), .06

2 Mother Years in the U.S. .12 (.02), .37∗∗∗ .09 (.03), .28∗∗Mother Years of Education .08 (.05), .15 .05 (.05), .09

3 Mother English Slope 2.06 (.65), .27∗∗� R2 for step 2 or 3 .13∗∗∗ .05∗∗R2 total .15∗∗∗ .29∗∗∗ .34∗∗∗F(df ) 11.79 (2, 130) 12.83 (4, 128) 13.04 (5, 127)

Note. Values are unstandardized B coefficients, standard error of B (in parenthesis), and ß values from the final regressionequation.∗p < .05. ∗∗p < .01. ∗∗∗p < .001.

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DUAL LANGUAGE DEVELOPMENT 79

attenuated (ß = .23, p = .015) (bias corrected confidence interval [0.16, 0.64] indicates signifi-cant meditational effect of mothers’ years in the United States). In the final step, mothers’ Englishlinear slope predicted (ß = .27, p = .002) as did mothers’ years in the United States (ß = .28, p= .001). Dominican status attenuated to nonsignificance. The overall model was significant, F(5,127)=13.04, p < .001, and accounted for 34% of the variance.

To summarize, mothers’ linear slopes in English and Spanish across the four ages (representingchanges to English and Spanish word types per minute) were associated with children’s linearslopes (i.e., growth in word types per minute) in the respective language. Mexican status wasassociated with greater growth in Spanish compared to Dominican status, whereas Dominicanstatus predicted greater growth in children’s English. However, these ethnic differences werelargely explained by mothers’ years in the United States, which were in turn associated withmore Spanish (Mexican) or English (Dominican) use in mothers. Female status was associatedwith children’s linear slopes in Spanish only.

Prediction to Children’s School Readiness Skills

To address the main aim of the study, we examined associations between growth in children’sEnglish and Spanish word types per minute (i.e., linear slopes) and children’s expressive vocab-ulary (EOWPVT), emergent literacy skills (WJ Letter Word Identification and narrative skillin independent storytelling), and emergent math skills (WJ Applied Problems and QuantitativeReasoning) at 5 years of age.

Step 1 of regressions included female and Dominican status; Step 2 included mothers’ yearsin the United States and years of education; Step 3 included mothers’ linear slopes for Englishand Spanish. The final step (Step 4) examined whether children’s linear slope for Englishand Spanish word types per minute predicted above these measures, thereby representing avery conservative test of the role of children’s language growth in subsequent school readi-ness skills. When testing prediction to children’s narrative skill, the language of the child’sstory (English or Spanish) was also controlled. The results of the full models are presented inTable 3.

Expressive vocabulary. Dominican status predicted children’s EOWPVT scores in Step 1(ß = .27, p = .006). However, the advantage of Dominican children was no longer significant(ß = .10, p = .406) once mothers’ years in the United States (which was significant, ß = .24, p= .016) and years of education were entered in Step 2 (bias corrected confidence intervals are[0.27, 2.96] and [1.10, 7.15], respectively, indicating both are significant mediators). In Step 3,mothers’ linear slope for Spanish inversely predicted children’s scores (ß = –.32, p = .006), andyears in the United States was attenuated to nonsignificance (ß = .11, p = .295). In the finalstep, the linear slope of children’s English word types per minute predicted children’s EOWPVTscores (ß =.28, p = .032), whereas the linear slope for Spanish did not predict (ß =.19, p =.149). However, the magnitude of effect sizes for prediction from the English linear slopes ver-sus Spanish linear slope (i.e., ß = .28 vs. .19) did not differ statistically, based on the Fishertest contrasting associations suggesting that growth in either language supported this outcome.The overall model was significant, F(8, 94) = 4.66, p < .001, and accounted for 22% of thevariance.

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TAB

LE3

Chi

ldre

n’s

Lang

uage

Gro

wth

inE

nglis

han

dS

pani

shas

Pre

dict

ors

ofS

choo

lRea

dine

ssS

kills

Step

Vari

able

sE

xpre

ssiv

eL

angu

age

WJ

Let

ter

Wor

dN

arra

tive

Skil

laW

JQ

uant

itat

ive

Rea

soni

ngW

JA

ppli

edP

robl

ems

1D

omin

ican

.07

(3.7

2),.

002

−1.8

4(2

.46)

,−.1

0.1

0(1

.11)

,.01

−3.1

0(2

.88)

,−.1

3−3

.16

(2.8

5),−

.14

Fem

ale

−3.7

8(2

.92)

,−.1

2−1

.38

(1.9

3),−

.07

1.86

(.87

),.2

0∗−1

.38

(2.2

6),−

.06

−3.7

8(2

.20)

,−.1

72

Mot

her

Yea

rsin

the

U.S

..1

1(.

30),

.04

−.14

(.20

),−.

08.2

1(.

09),

.27∗

.07

(.23

),.0

4−.

02(.

23),

−.01

Mot

her

Yea

rsE

duca

tion

.71

(.55

),.1

5.1

3(.

36),

.05

.21

(.17

),.1

5.4

1(.

43),

.12

.14

(.42

),.0

43

Mot

her

Eng

lish

Slop

e7.

56(8

.27)

,.13

14.6

8(5

.48)

,.41

∗∗−3

.87

(2.5

7),−

.23

22.5

8(6

.40)

,.53

∗∗16

.54

(6.2

6),.

40∗

Mot

her

Span

ish

Slop

e−1

.39

(.77

),−.

22.5

2(.

51),

.13

.13

(.23

),.0

71.

07(.

59),

.23

.88

(.58

),.2

04

Chi

ldE

nglis

hSl

ope

2.21

(1.0

2),.

28∗

1.07

(.67

),.2

3.8

7(.

32),

.39∗

∗1.

12(.

79),

.20

2.19

(.77

),.3

9∗∗

Chi

ldSp

anis

hSl

ope

2.42

(1.6

7),.

193.

71(1

.10)

,.47

∗∗.7

8(.

50),

.21

4.73

(1.2

9),.

50∗∗

∗4.

88(1

.28)

,.52

∗∗∗

R2

�fo

rst

ep4

.04

.11∗

∗.0

6∗.1

2∗∗

.15∗

∗R

2to

tal

.28∗

∗∗.1

3.3

0∗∗∗

.18∗

.18∗

F(d

f)4.

66(8

,94)

1.75

(8,9

4)4.

12(9

,86)

2.65

(8,9

4)2.

58(8

,93)

Not

e.V

alue

sar

eun

stan

dard

ized

Bco

effic

ient

s,st

anda

rder

ror

ofB

(in

pare

nthe

sis)

,and

ßva

lues

from

the

final

regr

essi

oneq

uatio

n.a T

hela

ngua

gein

whi

chch

ildre

nto

ldth

est

ory

(Eng

lish

orSp

anis

h)w

asen

tere

din

Step

1pr

edic

ting

child

ren’

sN

arra

tive

Skill

s.T

heun

stan

dard

ized

Bco

effic

ient

s,st

anda

rder

ror

ofB

(in

pare

nthe

sis)

,and

ßva

lues

for

this

vari

able

inth

efin

alm

odel

are

.24

(1.0

9),.

02.

∗ p<

.05.

∗∗p<

.01.

∗∗∗ p

<.0

01.

80

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DUAL LANGUAGE DEVELOPMENT 81

Emergent literacy. Prediction to measures of emergent literacy was examined for WJ LetterWord Identification Skills and children’s narrative skills. For WJ Letter Word Identification,neither demographics measures (female status, mother ethnicity, mothers’ years in the UnitedStates, mothers’ years of education) nor mothers’ linear slopes for English and Spanish weresignificant in the first 3 steps. However, in the final step, the linear slope of children’s growthin Spanish (ß = .47, p = .001), but not English (ß = .23, p = .115), predicted this out-come. Mothers’ growth in English word types also predicted in the final model (ß = .41,p = .009). The full model was not significant due to limited prediction of other variables inthe model (ethnicity, years education, years in United States). However, the third step of themodel was significant, F(2, 94) = 5.70, p = .005, and the overall model accounted for 13% of thevariance.

We next examined prediction to children’s narrative skill, derived from children’s performanceon the independent storytelling task. The majority of children (66.3%) told the Hug story inEnglish, and the remaining children (33.7%) told the Hug story in Spanish. Moreover, both moth-ers’ growth in English word types (beta = .33, p = .020) and children’s growth in English wordtypes (beta = .32, p = .015) predicted telling the story in English. Therefore, language of storyalso served as a control in analyses.

Findings revealed that female status predicted in Step 1(ß = .27, p = .007), and retainedits significance (ß = .30, p = .003) when mothers’ years in the United States (also significant,ß = .27, p =.015) and years of education were entered in Step 2. In Step 3, female status (ß = .27,p = .005), mothers’ years in the United States (ß = .36, p = .002), and mothers’ English linearslope (inversely, ß = –.35, p = .010) were associated with children’s narrative scores. The finalstep indicated that children’s growth in English word types (ß = .39, p = .007) predicted nar-rative skill, but growth in Spanish word types did not (ß = .21, p = .122). Again, however,the magnitude of effects for English and Spanish did not differ statistically based on the Fishertest contrasting associations; this suggests that language growth more generally supported thisoutcome.

Females continued to have higher narrative scores than males (ß = .20, p = .036), as didchildren whose mothers had been in the United States longer (ß = .27, p = .022). Mothers’linear slopes for English no longer predicted in the final step. The overall model was significant,F(9,86) = 4.12, p < .001, and accounted for 30% of the variance.

Math skills. For the math assessment of the WJ Quantitative Reasoning, none of the inde-pendent variables predicted in Steps 1, 2, and 3. In the final step, children’s growth in Spanish(ß = .50, p < .001) predicted, but growth in English did not (ß = .20, p = .158). The magnitudeof effects differed significantly when comparing beta values for the two predictors in a Fishertest, indicating a clear benefit of Spanish language growth for this measure. Mothers’ growthin English (ß = .53, p = .001) also predicted. The full model was significant, F(8, 94) = 2.65,p = .012, and accounted for18% of the variance.

For children’s WJ Applied Problems, significant predictors only emerged in the final step.Children’s growth in Spanish (ß = .52, p < .001) and English (ß = .39, p = .005) both predicted,as did mothers’ rate of growth in English (ß = .40, p = .010). The full model was significant,F(8, 93) = 2.58, p = .014, and accounted for 18% of the variance.

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82 TAMIS-LEMONDA ET AL.

DISCUSSION

The current findings support the premise that Latino children’s growth of vocabulary, in Englishand Spanish, predicts a variety of cognitive skills at age 5 years, and underscores the importanceof maternal language for children’s language development. Our findings also contribute to thegrowing literature showing that dual language learning children vary in the amount and qualityof language they hear in each language, their relative exposure to the two languages, and whetherthey hear their languages from one or more people who are native or nonnative speakers (DeHouwer, 2009; Place & Hoff, 2011). In turn, children’s relative exposure in each language pre-dicts their skills in the respective languages (De Houwer, 2009; Hurtado et al., 2008; Marchmanet al., 2010; Pearson et al., 1997; Place & Hoff, 2011; Song et al., 2012).

Specificity of Prediction

Notably, children’s vocabulary growth (i.e., linear slopes for word types per minute in Englishand Spanish) predicted multiple cognitive skills (i.e., language, literacy, math), even after con-trolling for mothers’ language change (linear slopes). Moreover, there was specificity in thenature of these associations, which may be explained by the types of skills being assessed.Children’s growth in Spanish predicted their performance on the Woodcock Johnson Letter WordIdentification and Quantitative Reasoning tasks. The Letter Word Identification test requires lit-eracy skills (e.g., being able to identify letters and read simple printed words, such as cat or dog),and Quantitative Reasoning draw on math skills that are symbol- and/or word based (i.e., recog-nizing numbers and simple equations such as 2 + 2; “what number comes next?”; “how many areleft?”). In this regard, both tasks measure specialized skills that may be supported by children’scontinued growth in their first language, Spanish. These specialized skills may have transferredacross-languages for children tested in English (the majority), or supported the responses of chil-dren tested in Spanish. Perhaps, because most of the children had switched from using Spanishto using English over the course of the study, their emerging English did not yet get them to thesame place in literacy and math as did their continued Spanish growth. This might especially bethe case if Latino children learn the English vocabulary words for numbers (for example) onlyafter they have learned those words in Spanish.

In contrast, growth in English and/or both English and Spanish predicted children’s perfo-mance on language-based skills, namely expressive language (EOWPVT), narratives (indepen-dent storytelling task), and the Woodcock Johnson Applied Problems test. These assessmentscommonly tap children’s skills at using oral language in the service of vocabulary (EOWPVT),the production of meaningful stories (narratives), or solving simple problems (Applied Problems).Perhaps Latino children’s growth in English first supports in-kind language-related skills (e.g.,vocabulary growth and narratives), and later transfers to skills that require specialized knowledgeand words (e.g., letter-word identification and math).

However, these interpretations are speculative, and further research is needed on whether spe-cific associations maintain in larger samples. Here, sample size may have limited power to detectsmall effects. In fact, the beta weights for both English and Spanish slopes for every child out-come were positive—ranging from .19 to .52. This suggests generalized benefits of vocabularygrowth for a variety of cognitive skills, even in the context of specificity.

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DUAL LANGUAGE DEVELOPMENT 83

Children’s Language Development in Sociocultural Context

Latino children’s vocabulary development—as all children—occurs in a broader socioculturalcontext, and we also considered several correlates of children’s English and Spanish vocabu-lary growth, including child gender and mothers’ language (linear slopes), ethnicity, years in theUnited States, and years of education.

In terms of child gender, girls exceeded boys in their growth of Spanish and independent sto-rytelling, which aligns with the female advantage in language development (e.g., Bornstein &Haynes, 1998; Fenson et al., 1994; Huttenlocher et al., 1991) and narrative skills (e.g., Reese &Fivush, 1993) that have been documented by others. Notably, this work advances on this litera-ture by indicating a specific female advantage in children’s home language of Spanish, but notEnglish. Future research is needed on the sources of gender differences in young Latino children’slanguage development.

In terms of mother–child associations, changes in mothers’ language across the four ages (i.e.,linear slopes for English and Spanish) predicted children’s vocabulary growth in the respectivelanguage, which highlights the importance of lexically diverse maternal talk for children’s lan-guage development. Of course, these findings are based on correlational data, which limits causalinferences: Shared biology and/or child effects might explain mother–child associations. Indeed,children who display rapid advances in language skills might induce more sophisticated languagefrom their mothers, thereby feeding into a continued cycle of growth. However, even if certainchildren benefit more readily from language input than others, and even if children who are moreadvanced in language skills “elicit” richer language from their mothers, child effects do not ruleout the vital role of mothers’ language in children’s language development. Children can onlylearn the words to which they are exposed, and mothers offer children a menu of words duringinteractions that scaffold children’s growth in vocabulary.

Additionally, mothers’ language use during booksharing had implications for children’s cog-nitive skills, even after controlling for children’s own language growth. In particular, mothers’linear slope in English from 2 to 5 years was associated with children’s performance on theWoodcock Johnson Letter-Word Identification, Quantitative Reasoning, and Applied Problemstests (although the magnitude of effects for English and Spanish growth did not differ statisti-cally in prediction of WJ Applied Problems). In contrast, mothers’ linear slopes in Spanish werenot associated with any child measure at age 5. What might explain the differential predictionof mothers’ English versus Spanish language growth? It may be that mothers who increasedin their English use were more able to offer children opportunities to develop skills in theareas being tested. In fact, when these mother–child dyads were engaged in a block construc-tion task at the 4-year assessment, English-speaking Latino mothers taught more literacy andmath concepts to their children than did Spanish-speaking mothers (Tamis-LeMonda, Sze, Ng,Kahana-Kalman, & Yoshikawa, 2013). It is also possible that mothers’ English use was asso-ciated with other measures (e.g., whether the child attended center-based care) that were notexamined here. Finally, the differential pattern of prediction might be due to the larger variationseen in mothers’ English slopes, which may have resulted in greater predictive power, comparedto mothers’ Spanish slopes, which were less varied. Indeed, mothers were all first generationimmigrants and spoke Spanish primarily in their childhoods, but differed in the levels of theirEnglish skills and/or English use due to a number of reasons (e.g., time in the United States,

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84 TAMIS-LEMONDA ET AL.

education, partner’s language, work status, and language). Mothers who displayed developmen-tal shifts from Spanish to English were likely skilled in English and thus able to offer theirchildren opportunities to develop skills in two languages. Further investigations will advancea deeper understanding of the association between Latino mothers’ English proficiency and childskills.

In terms of distal sources of variation, although all mothers were immigrants who learnedSpanish as their first language, mothers’ ethnicity was associated with different profiles of mater-nal English and Spanish word usage. Dominican mothers grew faster in English language use overtime than did Mexican mothers, an ethnic difference that reflects the different backgrounds andexperiences of these mothers. Dominican mothers resided in the United States longer than hadMexican mothers, and completed more years of education as well. Mediation analyses indicatedthat these two contextual variables explained much of the variance in mothers’ use of Englishversus Spanish. These findings highlight the need to move beyond pan-ethnic characterizationsof children’s language experiences and development.

Explanatory Mechanisms

Together, findings indicate the role of mothers’ language in children’s language growth in Latinofamilies, as well as the predictive validity of children’s early language growth for their latercognitive skills. Why might children’s growth in vocabulary predict these cognitive skills? Atthe outset we suggested that vocabulary growth feeds into the early emergence of an efficientcortical network for language (Dehaene-Lambertz et al., 2010), which in turn facilitates the learn-ing of new information. Children who know more words are more efficient during real-timeprocessing of new lexical information, perhaps because vocabulary helps fine-tune speech pro-cessing skills and enables children to more reliably access and integrate multiple cues to meaning(Dapretto & Bjork, 2000). Conversely, children with limited vocabularies are less able to learnnew words (Gershkoff-Stowe & Hahn, 2007), and in turn are at a disadvantage for later cognitiveperformance (Marchman & Fernald, 2008).

It may also be that children vary in their early abilities to attend to, store and manipulate infor-mation, which then feeds into word processing and growth of vocabulary, as seen in researchwith typical and atypical populations (e.g., Gathercole, 2006) as well as habituation studies indi-cating associations between speed of processing in infancy and vocabulary growth in the firstyear (Tamis-LeMonda & Bornstein, 1989). Similarly, children who are quick at tracking distri-butional regularities in the speech signal and at monitoring cues to meanings or grammaticalcategories may be those who are efficient at online language processing (e.g., Marchman et al.,2010; Smith & Yu, 2008). If so, an early biological advantage in processing abilities, coupledwith rich language input, might portend rapid vocabulary growth and cognitive skill.

Limitations

This study contributes to the relatively sparse literature on developmental connections betweenvocabulary growth and cognitive skills in dual language learning children, yet also contains sev-eral limitations. In terms of sampling, we focused on two specific Latino groups in a Northeastcity in the United States, which limits generalizability. Moreover, measures of children’s

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DUAL LANGUAGE DEVELOPMENT 85

vocabulary growth and mothers’ language use were based on transcriptions of expressed language(word types) during booksharing interactions. Although there is widespread evidence for thevalidity of observational measures of language, these interactions were based on a narrow sam-pling of speech between children and mothers. Clearly, language interactions during booksharingdiffer from interactions in other contexts (e.g., Tamis-LeMonda & Song, 2012), raising questionsabout the extent to which language in this setting is generalizable. Although we ran ancillaryanalyses to address this limitation, future studies should focus on language interactions across abroader range of contexts. Moreover, children interact with multiple language partners over thecourse of the day, and a more comprehensive portrayal of their language experiences and develop-ment necessitates understanding the language provided by these different partners. For example,our own research, as well as that of others, has highlighted the unique role that fathers play inchildren’s vocabulary development (e.g., Tamis-LeMonda et al., 2012), and has shown that inLatino families, fathers’ interactions with children might be especially important for children’sexposure to and growth in English (Song et al., 2012). Beyond fathers, children’s interactionswith siblings, grandparents, and other relatives are influential.

CONCLUSIONS

The current findings highlight the importance of Latino children’s early vocabulary growth forlater cognitive skills. Thus, the predictive validity of early vocabulary is robust, rather than anepiphenomenon of environmental stability. Moreover, findings refute notions that dual languageexposure early in development is harmful to and/or confuses children. That is, all children westudied were born to first generation, Spanish-speaking immigrant mothers, yet many showedgains in both English and Spanish vocabularies, and measures of vocabulary growth in bothlanguages predicted cognitive skills at age 5 years, albeit in some specific ways. Indeed, duallanguage learning children who experience early exposure to English display greater languagemastery (McDonald, 2000; Petitto & Kovelman, 2003) and greater tissue density in regions ofthe brain related to language, memory, and attention ages (Mechelli et al., 2004) than do childrenexposed to a second language at later ages. Consequently, scholars endorse efforts to improvethe English language skills of dual language children early in development by exposing them tonative English speakers, while also encouraging their parents to speak the language they knowbest as a vehicle for expanding children’s vocabularies (Place & Hoff, 2011).

In closing, our findings augment the growing evidence that rich language input benefits chil-dren by promoting growth in vocabulary that snowballs into enhanced cognitive skills in multipledomains. “Growing a lexicon(s)” is a fundamental task of early development and a precursor tochildren’s future learning of school-related skills, whether children are monolingual or exposedto two or more languages.

ACKNOWLEDGMENTS

This research was conducted at New York University’s Center for Research on Culture,Development and Education. We acknowledge students at the Center who gathered and codeddata over the 5-year study, including Jenny Arevolo, Cristina Hunter, Fernanda Lucchese, and

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86 TAMIS-LEMONDA ET AL.

Irene Wu. We are grateful to the hundreds of mothers and children who have participated in thisproject.

FUNDING

We acknowledge funding from NSF BCS grant #021859 and NSF IRADS grant #0721383.

REFERENCES

Bates, E., & Goodman, J. (1999). On the emergence of grammar from the lexicon. In B. MacWhinney (Ed.), Theemergence of language (pp. 29–79). Mahwah, NJ: Lawrence Erlbaum.

Bornstein, M. H., & Haynes, M. O. (1998). Vocabulary competence in early childhood: Measurement, latent construct,and predictive validity. Child Development, 69, 3, 654–671.

Brownell, R. (2000). Expressive one-word picture vocabulary test: Bilingual edition (EOWPVT) (3rd ed.). Novato, CA:Academic Therapy Publications.

Cabrera, N. J., Shannon, J. D., West, J., & Brooks-Gunn, J. (2006). Parental interactions with Latino infants: Variation bycountry of origin and English proficiency. Child Development, 77(5), 1190–1207.

Dapretto, M., & Bjork, E. L. (2000). The development of word retrieval abilities in the second year and its relation toearly vocabulary growth. Child Development, 71(3), 635–648.

Dehaene-Lambertz, G., Montavont, A., Jobert, A., Allirol, L., Dubois, J., Hertz-Pannier, L., & Dehaene, S. (2010).Language or music, mother or Mozart? Structural and environmental influences on infants’ language networks. Brainand Language, 114(2), 53–65.

De Houwer, A. (2009). Bilingual first language acquisition. Bristol, England: Multilingual Matters.Fenson, L., Dale, P. S., Reznick, J. S., Bates, E., Thal, D. J., & Pethick, S. J. (1994). Variability in early communicative

development. Monographs of the Society for Research in Child Development, 59(5), 1–173.Friedrich, M., & Friederici, A. D. (2010). Maturing brain mechanisms and developing behavioral language skills. Brain

and Language, 114(2), 66–71.Garcia-Sierra, A., Rivera-Gaxiola, M., Percaccio, C. R., Conboy, B. T., Romo, H., Klarman, L., . . . Kuhl, P. K. (2011).

Bilingual language learning: An ERP study relating early brain responses to speech, language input, and later wordproduction. Journal of Phonetics, 39(4), 546–557.

Gathercole, S. E. (2006). Nonword repetition and word learning: The nature of the relationship. Applied Psycholinguistics,27(4), 513–543.

Gershkoff-Stowe, L., & Hahn, E. R. (2007). Fast-mapping skills in the developing lexicon. Journal of Speech, Language,and Hearing Research, 50(3), 682–697.

Grosjean, F. (2010). Bilingual: Life and reality. Cambridge, MA: Harvard University Press.Hart, B., & Risley, T. R. (1995). Meaningful differences in the everyday experience of young American children.

Baltimore, MD: Paul H. Brookes Publishing.Hayes, A. F. (2009). Beyond Baron and Kenny: Statistical mediation analysis in the new millennium. Communication

Monographs, 76(4), 408–420.Hernandez, D. J., Denton, N. A., & Macartney, S. E. (2008). Children in immigrant families: Looking to America’s

future. Social Policy Report, 21(1), 3–22.Hurtado, N., Marchman, V. A., & Fernald, A. (2008). Does input influence uptake? Links between maternal talk,

processing speed and vocabulary size in Spanish-learning children. Developmental Science, 11(6), F31–F39.Huttenlocher, J., Haight, W., Bryk, A., Seltzer, M., & Lyons, T. (1991). Early vocabulary growth: Relation to language

input and gender. Developmental Psychology, 27(2), 236–248.Jia, G., Aaronson, D., & Wu, Y. (2002). Long-term language attainment of bilingual immigrants: Predictive variables and

language group differences. Applied Psycholinguistics, 23(4), 599–621.MacWhinney, B. (2000). The CHILDES project: Tools for analyzing talk (3rd ed.). Mahwah, NJ: Erlbaum.Marchman, V. A., & Fernald, A. (2008). Speed of word recognition and vocabulary knowledge in infancy predict cognitive

and language outcomes in later childhood. Developmental Science, 11(3), F9–F16.

Dow

nloa

ded

by [

Col

umbi

a U

nive

rsity

] at

10:

13 1

2 A

ugus

t 201

5

DUAL LANGUAGE DEVELOPMENT 87

Marchman, V. A., Fernald, A., & Hurtado, N. (2010). How vocabulary size in two languages relates to efficiency inspoken word recognition by young Spanish-English bilinguals. Journal of Child Language, 37(4), 817–840.

Marchman, V. A., Martínez-Sussmann, C., & Dale, P. S. (2004). The language-specific nature of grammaticaldevelopment: Evidence from bilingual language learners. Developmental Science, 7(2), 212–224.

McDonald, J. L. (2000). Grammaticality judgments in a second language: Influences of age of acquisition and nativelanguage. Applied Psycholinguistics, 21(3), 395–423.

Mechelli, A., Crinion, J. T., Noppeney, U., O’Doherty, J., Ashburner, J., Frackowiak, R. S., & Price, C. J. (2004).Structural plasticity in the bilingual brain: Proficiency in a second language and age at acquisition affect grey-matterdensity. Nature, 431(7010), 757.

Morisset, C. E., Barnard, K. E., & Booth, C. L. (1995). Toddler’s language development: Sex differences within socialrisk. Developmental Psychology, 31(5), 851–865.

Pan, B., Rowe, M., Spier, E., & Tamis-LeMonda, C. S. (2004). Measuring productive vocabulary of toddlers in low-income families: Concurrent and predictive validity of three sources of data. Journal of Child Language, 31(3), pp.587–608.

Parra, M., Hoff, E., & Core, C. (2011). Relations among language exposure, phonological memory, and language devel-opment in Spanish-English bilingually developing two year olds. Journal of Experimental Child Psychology, 108(1),113–125.

Patterson, J. L., & Pearson, B. Z. (2004). Bilingual lexical development: Influences, contexts, and processes. In B.Goldstein (Ed.), Bilingual language development and disorders in Spanish-English speakers (pp. 77–104). Baltimore,MD: Paul Brookes.

Petitto, L. A., & Kovelman, I. (2003). The bilingual paradox: How signing-speaking bilingual children help us to resolvebilingual issues and teach us about the brain’s mechanisms underlying all language acquisition. Learning Languages,8(3), 5–18.

Place, S., & Hoff, E. (2011). Properties of dual language exposure that influence 2-year-olds’ bilingual proficiency. ChildDevelopment, 82(6), 1834–1849.

Preacher, K. J., & Hayes, A. F. (2008). Asymptotic and resampling strategies for assessing and comparing indirect effectsin multiple mediator models. Behavior Research Methods, 40(3), 879–891.

Raikes, H., Luze, G., Brooks-Gunn, J., Raikes, H. A., Pan, B. A., Tamis-LeMonda, C. S., . . . Rodriguez, E. T. (2006).Mother-child bookreading in low-income families: Correlates and outcomes during the first three years of life. ChildDevelopment, 77(4), 924–953.

Reese, E., & Fivush, R. (1993). Parental styles of talking about the past. Developmental Psychology, 29(3), 596–606.Rowe, M. L. (2008). Child-directed speech: Relation to socioeconomic status, knowledge of child development and child

vocabulary skill. Journal of Child Language, 35(1), 185–205.Smith, L., & Yu, C. (2008). Infants rapidly learn word-referent mappings via cross-situational statistics. Cognition, 106(3),

1558–1568.Smith, R. C. (2006). Mexican New York: Transnational lives of new immigrants. Berkeley, CA: University of California

Press.Song, L., Tamis-LeMonda, C. S., Yoshikawa, H., Kahana-Kalman, R., & Wu, I. (2012). Language experiences and vocab-

ulary development in Dominican and Mexican infants across the first 2 years. Developmental Psychology, 48(4),1106–1123.

StataCorp (2011). Stata Statistical Software (Release 12) [Computer software]. College Station, TX: StataCorp.Tamis-LeMonda, C. S., & Bornstein, M. H. (1989). Habituation and maternal encouragement of attention in infancy as

predictors of toddler language, play, and representational competence. Child Development, 60, 738–751.Tamis-LeMonda, C. S., Bornstein, M. H., & Baumwell, L. (2001). Maternal responsiveness and children’s achievement

of language milestones. Child Development, 72(3), 748–767.Tamis-LeMonda, C. S., & Song, L. (2012). Parent-infant communicative interactions in cultural context. In R. M. Lerner,

E. Easterbrooks, & J. Mistry (Eds.), Handbook of Psychology: Volume 6. Developmental Psychology (2nd ed.).Tamis-LeMonda, C. S., Song, L., Leavell, A. S., Kahana-Kalman, R., & Yoshikawa, H. (2012). Ethnic differences in

mother-infant communications are associated with infants’ language and gesture skills. Developmental Science, 15(3),384–397.

Tamis-LeMonda, C. S., Sze, I., Ng., F., Kahana-Kalman, R. K., & Yoshikawa, H. (2013). Maternal teaching during playwith 4-year olds: Variation by ethnicity and family resources. Merrill Palmer Quarterly, 59(3), 361–398.

Woodcock, R., Mather, N., & Wendling, B. (2001). Essentials of WJ III tests of achievement assessment. Itasca, IL:Riverside Publishing.

Dow

nloa

ded

by [

Col

umbi

a U

nive

rsity

] at

10:

13 1

2 A

ugus

t 201

5