Child Development, July/August 2015, Volume 86, Number 4, Pages 1094–1111

Bidirectionality in Self-Regulation and Expressive Vocabulary: Comparisons Between Monolingual and Dual Language Learners in Preschool Natalie L. Bohlmann, Michelle F. Maier, and Natalia Palacios University of Virginia

Significant differences in language and self-regulation skills exist among children when they enter formal schooling. Contributing to these language differences is a growing population of dual language learners (DLLs) in the United States. Given evidence linking self-regulatory processes and language development, this study explored bidirectional associations between English expressive vocabulary and self-regulation skills for monolingual English and DLL preschool children (N = 250) from mixed-income families in Los Angeles. Across three time points, findings provide initial support for bidirectionality between these developing skills for both monolinguals and DLLs. Results provide strong empirical support for vocabulary serving as a leading indicator of self-regulation skills in preschool. Findings also suggest that early self-regulation skills play a particularly important role for vocabulary development.

The preschool period is a time when children make significant progress in acquiring the foundational language skills vital for early and long-term school achievement (Biemiller, 2003; Duncan et al., 2007; NICHD Early Child Care Research Network [ECCRN], 2005; Storch & Whitehurst, 2002). It is also a time of rapid growth in self-regulatory abilities (Kochanska, Coy, & Murray, 2001) shown to predict school readiness and later academic success (Blair & Razza, 2007; Carlson, 2003). A growing body of research documents the relation between children’s early self-regulation and language development (e.g., McClelland et al., 2007; Raver et al., 2011). Concurrently, children’s language skills predict gains in children’s self-regulatory capacities (e.g., Vallotton & Ayoub, 2011), suggesting simultaneous growth and possible bidirectionality between the development of language and self-regulation. Theoretical models recognize the dynamic and inteNatalie Bohlmann is now at Department of Educational Theory and Practice, College of Education, Montana State University, Billings. Michelle Maier is at MDRC, New York, NY. This study was supported by two grants to the University of Virginia: one from the National Institute of Child Health and Human Development and the Interagency Consortium on Measurement of School Readiness (R01 HD051498), and the other from the Institute of Education Sciences, U.S. Department of Education (R305A060021) funding of the National Center for Research on Early Childhood Education (NCRECE). The opinions expressed are those of the authors and do not represent views of the funding agencies. The authors thank Jason Downer for his feedback on earlier drafts of this manuscript and the generous programs and teachers who participated in this study. Correspondence concerning this article should be addressed to Natalie L. Bohlmann, Department of Educational Theory and Practice, College of Education, MSU Billings, 1500 University Ave, Billings, MT 59101. Electronic mail may be sent to [email protected].

grated nature of these skills in early childhood (Fischer & Bidell, 2006), yet research testing a possible bidirectional relation between the two, particularly through the use of longitudinal data, is limited (Fuhs & Day, 2011; Fuhs, Nesbitt, Farran, & Dong, 2014; Weiland, Barata, & Yoshikawa, 2014). Significant differences in both language and selfregulation exist among children when they enter formal schooling (August, Shanahan, & Escamilla, 2009; Calkins & Howes, 2004; NICHD ECCRN, 2001). Contributing to the differences in language is the growing number of dual language learners (DLLs) in the United States (National Clearinghouse for English Language Acquisition and Language Instruction Educational Programs, 2006), many of whom enter school having limited English proficiency (Hernandez, Denton, & McCartney, 2007). Given the variability in language development among DLL and monolingual populations (Hammer & Miccio, 2006; NICHD ECCRN, 2001) and evidence suggesting differences in the rate of growth of self-regulation between monolingual English and DLL preschoolers (Wanless, McClelland, Tominey, & Acock, 2011), this article seeks to examine the relations between language and selfregulation in early childhood within these two populations. Specifically, the current study explored bidirectional links between English language expressive vocabulary and self-regulation skills for monolingual and DLL preschoolers. © 2015 The Authors Child Development © 2015 Society for Research in Child Development, Inc. All rights reserved. 0009-3920/2015/8604-0008 DOI: 10.1111/cdev.12375

Bidirectionality in Self-Regulation and Vocabulary

A Dynamic Skills Framework This study is grounded in theoretical models that highlight the dynamic and interactive nature of skills development within the varied contexts of children’s experiences. Dynamic skill theory describes development as the construction of progressively more complex skills organized into strands that build a developmental web. Children develop along multiple strands simultaneously. The nature of children’s development is dynamic where developing skills in one strand influence developing skills in another (Fischer & Bidell, 2006). Moreover, children’s development is marked by variability in skills across these strands as children are influenced by the varied context in which they live (Fischer & Bidell, 2006). Thus, consistent with other developmental systems theories, dynamic skill theory is an alternative to developmental views that study different components of children’s development as if they were separate or merely linearly related and that treat the organism as separate from the context of development. Instead, it attempts to describe the interactive nature of developing skills, allowing for the nature of that interaction to change over time and across contexts. In the present study, language and self-regulation are viewed as dynamic skills simultaneously developing within the preschool period. Importantly, the association between children’s English expressive vocabulary and self-regulation skills is examined within a framework that takes into account the linguistic context (monolingual vs. DLL). Thus, these psychological processes are viewed, from a dynamic skill framework, as dynamic, constructive, and contextually embedded, giving rise to patterns of variability in developmental pathways. Prior research has been limited in its ability to test the dynamic nature of vocabulary and self-regulation skill development across time due to sample limitations. The present study overcomes these limitations by examining bidirectional relations between these skills across three assessment periods for both DLL and monolingual English-speaking children, thereby recognizing that variability may be found in the nature of these relations across time and across linguistic groups. Development of Self-Regulation in Early Childhood Upon entry into formal schooling, self-regulation emerges as a critical developmental marker. Although there is ongoing debate regarding the definition and components constituting self-regula-

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tion, a review of the literature suggests that the ability to control one’s own behavior, including initiating, ceasing, or modulating behavior in compliance with adult demands or in response to environmental demands, is a core component of early self-regulation (Blair & Razza, 2007; Kochanska et al., 2001; Smith-Donald, Raver, Hayes, & Richardson, 2007). Another aspect of self-regulation examined in research is individual differences in the regulatory strategies used to exert control over reactivity-based responses (Calkins & Howes, 2004). In the present study, we draw upon a construct of self-regulation that incorporates the related processes of compliance and executive control. Compliance with caregiver’s requests is a prototypic form of self-regulation, requiring the capacity to inhibit or activate behavior in accord with adult standards (Kochanska et al., 2001). Executive control is characterized by inhibitory processes and is one of the component pieces of executive functioning (Raver et al., 2011). As such, executive control helps children to stop an incorrect dominant response in favor of a subdominant response and serves a primary cognitive function in controlling thought and action (Carlson & Moses, 2001). The literature supports the notion that self-regulation can be operationalized through the use of tasks that require children to control or inhibit behavioral responses not only to resist impulses, but also to comply with adult demands (McClelland et al., 2007; Smith-Donald et al., 2007). Research has examined the emergence of and growth in children’s regulatory abilities. Studies suggest that regulation shifts from externally controlled to internally based or self-regulation in toddlerhood and undergoes rapid development between ages 3 and 6 (e.g., Kochanska et al., 2001). During this period, children show dramatic increases in their ability to attend to activities, comply with adult demands and directives, and inhibit inappropriate behavior (Moilanen, Shaw, Dishion, Gardner, & Wilson, 2010). Susceptible to environmental factors, including parenting practices and poverty, early self-regulation processes differ significantly between children (Blair, 2002; Calkins & Howes, 2004), and substantial variation exists in the degree to which children enter kindergarten with adequate regulatory skills (Rimm-Kaufman, Pianta, & Cox, 2000). The development of self-regulation in early childhood is particularly important, as children who enter formal schooling without adequate regulatory skills are at greater risk for low levels of academic achievement (Blair & Razza, 2007). Children from

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low-income families are more likely to exhibit lower behavior regulation and inhibitory control in preschool and kindergarten as compared to their more economically advantaged peers (Moilanen et al., 2010; Sektnan, McClelland, Acock, & Morrison, 2010). In the United States, Hispanic children disproportionately come from low-income families (U.S. Census Bureau, 2011), placing them at greater risk for disparities in self-regulation (Wanless et al., 2011). Yet, research that has examined race and ethnic differences in self-regulation has found little evidence for differences in the initial status or growth in compliance and executive control in Hispanic populations once poverty status is controlled (Moilanen et al., 2010; Sektnan et al., 2010). Some evidence exists for accelerated development of self-regulation and related inhibitory control skills in bilingual populations as compared to monolingual populations (Bialystok, Barac, Blaye, & Poulin-Dubois, 2010; Carlson & Meltzoff, 2008). However, the same inhibitory control advantage was not found for DLLs enrolled in a Spanish–English immersion kindergarten (Carlson & Meltzoff, 2008). Bialystok (2001) reasons that this more rapid development of inhibitory control processes is a product of bilingual children’s extensive practice with inhibitory control in a linguistic context as bilingual speakers must routinely hold in mind the relevant language while simultaneously inhibiting the nonrelevant language. Consistent with this interpretation, recent work using a continuous rather than dichotomous measure of bilingualism found that bilingualism positively predicted DLL children’s executive functioning, with greater executive functioning skills being associated with greater degrees of bilingualism (White & Greenfield, 2014). Taken together, the constellation of these findings suggests a very complex picture of interactions between poverty, ethnic status, and language exposure. As the most populous and one of the fastest growing minority groups in the United States (U.S. Department of Commerce, 2012), longitudinal studies that focus on the development of self-regulation within a sample of mixed-income preschool children who are predominantly Hispanic would allow comparisons between children with different language experiences (monolingual vs. DLL) and add to the generalizability of existing research. Development of Vocabulary Skills in Early Childhood The early years are also a critical time for language development, marked by rapid changes in children’s vocabulary skills (e.g., Farkas & Beron,

2004; Pan, Rowe, Singer, & Snow, 2005). Expressive vocabulary, in particular, is an important early competency that helps establish a foundation for learning. This is evident in studies showing early expressive vocabulary—whether measured as expressive vocabulary skills or language production —to be a strong predictor of a host of outcomes in preschool and elementary school, including reading, language, and literacy (e.g., Biemiller, 2003; Duncan et al., 2007). Research has also shown relations between children’s expressive vocabulary and emergent social and behavioral skills (Dawson & Williams, 2008; Estrem, 2005). Furthermore, early vocabulary growth has been shown to be related to later vocabulary skill prior to kindergarten entry, even after controlling for child background factors (Rowe, Raudenbush, & Goldin-Meadow, 2012). This suggests that not only overall levels of expressive vocabulary skills, but also positive change in those skills, may be important for a range of child outcomes, with children entering preschool with higher vocabulary scores tending to maintain that advantage. There is considerable variability in vocabulary development, though, having the potential to impact developmental trajectories in areas related to academic achievement, such as reading (Biemiller, 2003; Storch & Whitehurst, 2002). Contextual differences in the home environment prior to schooling account for some of these differences. For example, socioeconomic status has been well documented as a risk factor. While children from lowincome families tend to have similar growth trajectories as their middle-income peers, there is a gap in their overall levels, with low-income children tending to start behind, with lower scores as early as 3 years of age (Farkas & Beron, 2004). DLLs also tend to score lower on measures of vocabulary in comparison to monolingual English- and Spanishspeaking children. These differences are found as early as preschool and continue into later grades (Mancilla-Martinez & Lesaux, 2011; Paez, Tabors, & L opez, 2007). This means that we are more likely to see variations in the vocabulary skills of DLLs from low-income homes, particularly those from Hispanic backgrounds (e.g., Hammer & Miccio, 2006). Bidirectionality in Vocabulary and Self-Regulation As a marker for development, children’s early self-regulation has been linked to the acquisition of various skills and knowledge including language. Children with greater self-regulatory abilities tend to get more out of environmental input than those

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with limited self-regulation (Blair, 2002; Bodrova & Leong, 2007; Raver et al., 2011). Numerous studies have examined young children’s self-regulation as a predictor of vocabulary development. Children’s early regulatory skills are positively associated with both concurrent and later vocabulary levels (Sektnan et al., 2010). Evidence suggests that young children who display greater self-regulation show more proficient acquisition (growth) of vocabulary than their less regulated peers (McClelland et al., 2007; Raver et al., 2011). Moreover, growth in self-regulation has been shown to positively predict growth in expressive vocabulary across the prekindergarten (pre-k) year (McClelland et al., 2007), and targeted interventions designed to improve low-income preschoolers’ regulatory skills have demonstrated significant benefits for children’s vocabulary development (Raver et al., 2011). While a large body of evidence establishes the association between self-regulation and young children’s language development, there is also a theoretical basis for the role of language in the development of self-regulation. Vygotsky (1934/ 1986) proposed language functions as a mental tool to be used in the service of self-regulation, allowing one to reflect on and modify behavior. It is theorized that a child’s internalization of a caregiver’s self-regulatory speech is facilitated by language development, serving to proactively regulate behavior (Bernier, Carlson, & Whipple, 2010). The transition from other- to self-regulation is supported by children’s growing representational abilities in early childhood made manifest in their use of language (Berk & Winsler, 1995; Winsler, Diaz, & Montero, 1997). Support for this is found in children as young as 3 years when they use self-regulatory private speech, speaking out loud to themselves to help regulate their behavior (Winsler et al., 1997). Given a strong theoretical perspective that language takes on a primary role in regulating children’s behavior in the preschool years, it is somewhat surprising that most studies have either tested nondirectional associations between language and self-regulation, or use language as a control variable, rather than directly testing the contribution of language to self-regulation (M€ uller, Jacques, Brocki, & Zelazo, 2009). However, some evidence in support of the theoretical model does exist. Research by Vallotton and Ayoub (2011) found evidence for a relation between early vocabulary skills and self-regulation in toddlerhood, with both concurrent and prior vocabulary positively related to self-regulation skills at 36 months. Moreover, children with more vocabulary skills show greater

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growth in self-regulation in comparison to their peers (Ayoub, Vallotton, & Mastergeorge, 2011). Young children’s vocabulary skills have also been shown to play a mediating role in the association between maternal autonomy support and the development of self-regulation (Matte-Gagne & Bernier, 2011). Related research on preschoolers’ executive functioning found verbal ability to be a significant predictor of change across a preschool year (Fuhs & Day, 2011). In addition, studies have found positive associations between language skills and self-regulation deficits in children with language-learning disorders (Singer & Bashir, 1999). The rapid growth in both vocabulary and selfregulatory skills that is seen during the preschool years (Farkas & Beron, 2004; Kochanska et al., 2001; Pan et al., 2005), combined with research that has explored possible associations between these two domains, suggests a possible reciprocal relation in the growth of language and self-regulation. Recent research by Fuhs and Day (2011) and Weiland et al. (2014) tested bidirectionality between verbal ability and executive functioning skills (inhibitory control, attention shifting, and working memory) across a preschool year. Support for a unidirectional relation emerged in both studies, but in the opposite direction. Fuhs and Day (2011) found verbal ability predicted executive functioning from fall to spring, but the path between executive functioning and verbal ability over the same time period was not significant. Weiland et al. (2014) found the opposite; executive function predicted receptive vocabulary across the pre-k year while the path between vocabulary and executive function was not significant. In both of these studies the analysis was limited to two time points. It is possible that additional time points are needed in order to more fully test a bidirectional thesis. To our knowledge, only one prior study has examined bidirectional relations across three time points. In a test of the relation between oral comprehension and executive function, Fuhs et al. (2014) found evidence of a bidirectional relation from fall to spring of the pre-k year, while only a unidirectional relation between executive function and oral comprehension remained across the kindergarten year (spring pre-k to spring kindergarten). Taken together, these studies provide support for bidirectional associations but with variability in the timing and potential strength of associations. With the above notable exceptions, most of the work examining the relations between language and self-regulation has called upon linear models of development, which fail to adequately capture the

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dynamic nature of these developing skills. In contrast, dynamic skill theory recognizes the potential interplay between these domains and would characterize the rapid growth of both language and self-regulation within the preschool period as a coactive process that is iterative in nature and would allow for shifts in influence over time (Ayoub et al., 2011; Fischer & Bidell, 2006). Moreover, dynamic skill theory calls attention to the diversity of contexts in which variation in the development of these processes occurs (Fischer & Bidell, 2006). From this perspective, differences between monolinguals and DLLs that emerge are viewed as adaptive and complex in the process of healthy development. To test these assumptions, and in doing so address an existing gap in the literature, we were interested in examining whether language supports the development of self-regulation, early self-regulation supports the development of language, or the two support one another over time, doing so in a sample of preschoolers and within language subgroups. Finding only unidirectional associations between language and self-regulation over time would be evidence to support language skills as predicting self-regulatory processes. Conversely, unidirectional relations between self-regulation and language would suggest that self-regulation was helping to advance language development. Finding bidirectional relations across the three time points would be evidence in support of coactive processes that influence each other and that the relation is iterative. Study Aims The overarching aim of this investigation was to examine possible bidirectionality between children’s English language expressive vocabulary and selfregulation skills, expressed through compliance and executive control, in a sample composed of mixedincome DLL and monolingual English preschoolers. Using a cross-lagged design, the current study first tested bidirectionality between children’s English expressive vocabulary and self-regulation skills in a combined sample of Hispanic DLL and non-Hispanic monolingual preschoolers. Based on evidence from unidirectional models suggesting that young children’s language and self-regulation skills go hand in hand, we expected to find evidence of a bidirectional relation between children’s expressive vocabulary and their self-regulation skills. One consequence of the growing population of DLLs in the United States is that many young children experience a shift in their language context

as they transition from the home where the primary language is typically not English into a schoolbased setting whose goal tends to be the promotion and support of English language development (Pacini-Ketchabaw & Armstrong de Almeida, 2006) and where long-term academic success is closely linked to the acquisition of English language skills (see Genesee, Lindholm-Leary, Saunders, & Christian, 2005, for review). In line with a child-incontext perspective, researchers have stressed the importance of testing the generalizability of developmental models across subpopulations rather than just assuming that one model fits all (Garcia Coll et al., 1996). In testing the relations between English expressive vocabulary and self-regulation skills, we are sensitive to the possibility that differences may exist between monolingual speakers as compared to DLLs. For example, tests of oral language yield lower performance scores for DLL children in comparison to other groups (Paez et al., 2007). In part this is a function of the way we assess children, but it opens up the question of whether this relation differs for DLL as compared to monolingual English speakers. Although we expect to find bidirectionality for both language groups, we anticipate that the variability in exposure to English language within and between the two groups, combined with exposure to multiple languages in the DLL group, may influence the timing within which these bidirectional processes emerge as well as potential differences in the strength of the relations across time. Therefore, a subgroup analysis comparing monolingual English speakers to Spanish–English DLLs was conducted to test the bidirectional relation between children’s English expressive vocabulary skills and their self-regulation skills in each of these groups.

Method Participants Data for this study were collected as part of a 2year project that followed preschool children across three time points and examined predictors of children’s classroom engagement. Initial data collection occurred in the fall of preschool at Time 1 (T1, fall 2007), followed by a second data collection in the spring (Time 2 [T2, spring 2008]), and a third during the fall of the subsequent academic year in the child’s 2nd year of preschool or in kindergarten (Time 3 [T3, fall 2008]). Parent consent was obtained for children in 101 classrooms with participating teachers. Four children (two girls and two

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boys) were randomly selected, when possible, from the pool of consented children in each classroom. Because the goal of the larger study was to examine classroom engagement in a sample of typically developing preschoolers, children were excluded from selection if parents indicated that their child had an active Individualized Education Plan in the fall of the preschool year (5% of consented children). The full sample included 381 children (192 girls and 189 boys, M = 50.09, SD = 6.56 age in months), 341 in T1, and 40 additional children were recruited in T2 (all children were tracked into T3) from a large urban area in the Western United States. Sixty-seven percent of the children were Hispanic, 15% White, non-Hispanic, 6% Asian, 3% African American, and 7% multirace or other. English was spoken in the majority of homes (61%), but Spanish was also a commonly used home language (65%). The average income-to-needs ratio (computed by taking the family income, exclusive of federal aid, and dividing this by the federal poverty threshold for that family) was 1.7 (SD = 1.5) with 48% of households having ratios lower than 1 (i.e., below the poverty line) and 69% of families having ratios lower than 2. From this full sample, two of the four children in each classroom were randomly selected (one boy and one girl per classroom when possible) to participate in direct assessments; these children were similar to the full sample, with the exception that subsample children tended to come from families with slightly higher incomes (M = 1.88, SD = 1.6), t(317) = 2.63, p ≤ .001. Analytic Sample This analysis used a subset of children identified as monolingual English speakers or as DLLs from the larger sample of children who were administered direct assessments. Monolingual English speakers were identified by their parents as speaking only English in the home. DLLs were identified by their parents or teachers as speaking Spanish only or Spanish in addition to English. The final analytic sample for the current study included 250 monolingual (n = 73) and DLL (n = 177) preschoolers assessed on expressive vocabulary and compliance/executive control tasks across three time points (fall Year 1 [T1], spring Year 1 [T2], fall Year 2 [T3]). Children’s ages ranged from 35 to 63 months (M = 51.00, SD = 6.24) at T1 and 51% were girls. Sixty-nine percent of the preschoolers were Hispanic or Latino, 15% were White, and 14% were other ethnicities (2% were missing on this

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variable). Maternal education was 12.75 years (SD = 3.13). Forty-five percent of parents reported a family income that fell below the poverty line; an additional 24% reported an income that resulted in an income-to-needs ratio between 1.0 and 2.0 (see Table 1 for sample statistics by linguistic population). Procedures Public and private schools were recruited from the greater Los Angeles metropolitan area. Permission was first secured from center directors or principals, followed by invitations to teachers. Teachers completed demographic surveys and received a small stipend of $25 for each completed survey. Parents or guardians of children in each classroom were given an informed consent form and short family demographic survey. Data collectors completed 2 full days of training on administration of the direct child assessments followed by an additional day of supervised live practice. Data collectors were assessed during live practice to ensure that test administration and scoring skills were reliable and standardized. At each time point children were brought to a quiet, private area and administered a direct assessment battery lasting approximately 40 min. Given the large number of Hispanic children, bilingual data collectors were assigned to classrooms with children identified as Spanish speaking. Where parents or teachers indicated that a child spoke Spanish, the data collector administered the Peabody Picture Vocabulary Test (PPVT) and Test de Vocabulario en Imagenes Peabody (TVIP), as well as both the English and Spanish versions of the Woodcock–Johnson/Woodcock–Mu~ noz Picture Vocabulary subtest. Children’s age-equivalent ceiling sets were compared across the PPVT and TVIP to determine which language to use when administering the self-regulation assessments. The self-regulation assessments were then administered in English if the PPVT was higher and in Spanish if the TVIP was higher. Monolingual English speakers identified by their parents as speaking only English in the home were administered self-regulation assessments only in English.

Measures Child Demographics Consenting parents completed a survey that provided information about their child’s date of birth,

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Table 1 Sample Descriptives by Linguistic Group Monolingual Child demographics

n

%

Male Race Hispanic White Other ethnicities Age (in months) Income-to-needs Maternal education

73 71 71 71 69 71 72

Dual language learner n

%

58

177

46

13 51 36

175 175 175 157 160 172

94 01 06

gender, race/ethnicity, and Individualized Educational Plan status, as well as maternal education and languages spoken in the home. Expressive Vocabulary Skills Children’s expressive vocabulary skills were directly assessed in English with the Picture Vocabulary subtest of the Woodcock–Johnson III Tests of Achievement (Woodcock, McGrew, & Mather, 2001). For DLLs, expressive vocabulary was also assessed in Spanish with the Bateria III Woodcock– Munoz; Vocabulario sobre dibujos subtest (Mu~ nozSandoval, Woodcock, McGrew, & Mather, 2005). These subtests are part of a widely used, individually administered assessment and demonstrate high internal reliability and acceptable validity (Schrank, McGrew, & Woodcock, 2001; Schrank et al., 2005). The Picture Vocabulary subtest measures word knowledge by asking children to name objects depicted in a series of pictures. Raw scores were converted into W scores, which are scaled using item response theory (IRT scaled). To promote easier comparisons across the outcomes, expressive vocabulary scores at each time point were converted to T scores. Compliance/Executive Control Two behavior regulation tasks from SmithDonald et al. (2007) Preschool Self-Regulation Assessment (PSRA) were used in this study—Pencil Tap and Toy Sort. Both tasks have been widely used with young children as measures of self-regulation. The Pencil Tap was used to assess children’s executive control (Blair, 2002; Diamond & Taylor, 1996). Executive control is an aspect of effortful control in that children must focus their attention to better handle conflicting stimuli in order to

M (SD)

51.38 (6.40) 3.43 (1.42) 15.53 (2.87)

M (SD)

50.84 (6.18) 1.02 (0.88) 11.59 (2.43)

suppress a dominant response and initiate a subdominant response (Blair & Razza, 2007; Eisenberg et al., 2004). The Pencil Tap task asks children to tap once when the experimenter says tap twice and tap twice when the experimenter directs to tap once, thus requiring children to inhibit a prepotent response and replace it with a planned alternative response. Children were given 3 practice trials and 16 scored trials. Scores represent the percent correct out of 16. The Toy Sort task, an activity where children are given 2 min to sort and put away small toys without playing with them, was used to assess children’s compliance (NICHD ECCRN, 1998). Compliance is also related to children’s effortful control by requiring children not only to resist impulses but to demonstrate that they have internalized and can comply with adult rules and demands (Kochanska et al., 2001). Scores for this task included latency (in seconds) for children to begin sorting and latency to complete sorting. Based on the PSRA factor structure reported by the measure developers (Smith-Donald et al., 2007) and previously published work using the PSRA battery (Raver et al., 2011), a compliance/executive control score was created by averaging the child’s standardized percent correct score on Pencil Tap and standardized reversed latency to complete the Toy Sort (fall [T1] r = .43; spring [T2] r = .46; fall [T3] r = .26). Higher scores indicate better compliance/ executive control. To promote easier comparisons across the outcomes, scores at each time point were converted to T scores. Data Analytic Plan Autoregressive cross-lagged regression models were conducted in Mplus Version 6.11 (Muthen & Muthen, 1998–2010). Cross-lagged pathways, which

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were of primary interest, represented the associations between expressive vocabulary at time t and compliance/executive control at time t + 1 as well as the reciprocal association, compliance/executive control at time t with expressive vocabulary at time t + 1. Cross-lagged pathways were allowed to vary across time to ascertain whether there were changes in reciprocal associations among these variables over the study period. Autoregressive pathways represented the associations between expressive vocabulary at time t and expressive vocabulary at time t + 1 as well as the associations between compliance/executive control at time t and compliance/executive control at time t + 1. These pathways were allowed to vary across time, as well. Covariates were added as predictors of both expressive vocabulary and compliance/executive control. Therefore, for example, any significant cross-lagged associations between expressive vocabulary at time t and compliance/executive control at time t + 1 (and vice versa) are above and beyond the variance explained by the association between compliance/executive control at time t  1 and expressive vocabulary at time t, after adjusting for covariates. Child age, gender, ethnicity (Hispanic or Latino as the reference group), language status, and income-to-needs ratio were entered as predictors at all assessment time points. Whether the child was in a preschool or kindergarten classroom at the third assessment was entered as a control variable for T3 assessments only. Due to the nature of collecting data across the 101 participating classrooms, there was large variability in the number of days between assessment time points for each child. Three variables were created to account for the number of days between assessments: (a) number of days between September 1 and T1 assessment dates, (b) number of days between T1 and T2 assessment dates, and (c) number of days between T2 and T3 assessment dates. By creating these time variables we are controlling for any variability in timing between children and within children across time. These variables were entered as control variables for each of their respective time points. Four conditional cross-lagged models were estimated to determine which model best represented the associations between expressive vocabulary and compliance/executive control in these data: no coupling (i.e., no cross-lag associations between expressive vocabulary and compliance/executive control), unidirectional coupling (expressive vocabulary predicting compliance/executive control only),

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unidirectional coupling (compliance/executive control predicting expressive vocabulary only), and bidirectional coupling (i.e., full coupling). Model fit was compared across the four models using chisquare difference tests and by comparing standard fit indices: comparative fit index (CFI), standardized root mean square residual (SRMR), and root mean square error of approximation (RMSEA). When comparing two models against one another, CFI values over 0.90 or 0.95, as well as SRMR and RMSEA values of 0.08 or lower, reflect better model fit (Hu & Bentler, 1999; Kline, 2005). Once a final model was chosen, multiple-group analysis was conducted to simultaneously estimate within a single model whether reciprocal associations differed between monolinguals and DLLs. Intraclass correlations (ICCs) for expressive vocabulary and compliance/executive control at each time point suggest minimal impact of classroom-level clustering (ICCs range from 0.17 to 0.34). Being conservative, the multilevel nature of the data (children nested within classrooms) was taken into account by specifying the TYPE = COMPLEX analysis command in Mplus (Muthen & Muthen, 1998–2010). This procedure addresses nonindependence (clustering) by using a sandwich estimator in the analysis to compute robust standard errors (Muthen & Muthen, 2007). Additionally as a robustness check we tested the model in the DLL sample only controlling for Spanish expressive vocabulary to ascertain that home language would not change the nature of the results. In testing the model we ran four autoregressive cross-lagged models on the DLL sample while controlling for the effect of expressive vocabulary scores in Spanish (as measured by the Woodcock– Mu~ noz Picture Vocabulary subtest) on English vocabulary scores and self-regulation scores across all time points. Comparison fit indices were used to determine which model best fit the data. Missing Data Thirty percent of study children were missing direct assessment scores (i.e., expressive vocabulary and compliance/executive control) at T1, 26% at T2, and 38% at T3. Missing data at T1 were due to children being added to the study at T2. As expected in longitudinal studies, missing data at T2 and T3 were due largely to child attrition (leaving the preschool program) and multiple absences. Some children were also missing information on other study variables: child age (10%), ethnicity (2%), and income-to-needs ratio (8%).

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Missing data were determined to be missing at random by examining bivariate correlations and finding missingness on expressive vocabulary and compliance/executive control variables to be positively related to some of the variables in the sample: child ethnicity, gender, age, and kindergarten entry at T3. Full information maximum likelihood estimation was utilized to account for these missing data (e.g., McArdle et al., 2004). This type of estimation uses all available data for each case when estimating parameters and, therefore, increases the statistical power of estimated parameters (Enders & Bandalos, 2001). Additionally, the inclusion of these correlated variables as auxiliary variables in analyses helps to attenuate bias (Collins, Schafer, & Kam, 2001; Enders, 2010), resulting in estimates that are less biased compared to other approaches used to address missing data (e.g., listwise deletion, single imputation, or mean imputation) (McCartney, Burchinal, & Bub, 2006).

Results Descriptives Descriptive statistics and correlations can be found in Table 2. Expressive vocabulary and compliance/executive control are significantly and positively correlated with one another at each time point. Child age and family income-to-needs ratio are positively associated with all outcomes at the three time points. Autoregressive Cross-Lagged Regression Models Comparison of fit indices and chi-square difference tests across the four models (no coupling, bidirectional coupling, and the two unidirectional coupling models) suggested that the bidirectional model had the best fit (highest CFI and lowest RMSEA and SRMR) and demonstrated significant improvement in model fit over prior models; see Table 3. The bidirectional model results (see Figure 1) showed that almost all the autoregressive pathways were significant (ps < .001), which indicates that children’s scores at the previous assessment were positively associated with their scores at the subsequent assessment. The one exception was the path from compliance/executive control at T2 to T3, which was nonsignificant. There was also a significant concurrent association at T1 between expressive vocabulary and compliance/executive

control (r = .28, p < .001), indicating that at the beginning of the study children with higher expressive vocabulary scores tended to have higher compliance/executive control scores. Crosslagged pathways showed that higher compliance/ executive control scores were related to higher expressive vocabulary at all time points. A 1 SD unit increase in self-regulation was associated with 0.07 and 0.12 SD unit increases in expressive vocabulary at T2 and T3, respectively. The reciprocal association was not as consistent, with expressive vocabulary at T2 significantly and positively related to compliance/executive control at T3 only. A 1 SD unit increase in expressive vocabulary was associated with a 0.53 SD unit increase in selfregulation at T3. Multiple-Group Analysis The second aim of this article was to examine potential differences in the pattern of associations between DLL and monolingual English-speaking children. Multiple-group analysis simultaneously estimated bidirectional, autoregressive cross-lagged models for monolinguals and DLLs. Two models were conducted: A model in which all path coefficients were free to differ between groups was compared with a model where all paths (autoregressive, cross-lagged, and concurrent associations) were constrained to be the same for both the DLLs and the monolinguals. (The effects of the covariates were constrained to be the same across the two groups in both models.) A chisquare difference test calculated using the Satorra–Bentler scaling correction factor in Mplus (Satorra & Bentler, 2001) indicated that the fully constrained model had better fit than the model with the paths unconstrained, Dv2(5) = 13.513, p = .02, CFI = 0.91, RMSEA = 0.07, SRMR = 0.12, suggesting that there is no difference in the nature of these relations between groups. Thus, we will interpret and discuss the results from the bidirectional model of the full sample as described above. Robustness Check for DLL Group To examine the association between language competence in English and self-regulation in the DLL group while also accounting for language abilities in Spanish, we ran the four autoregressive crossed lag models on only the DLL sample while controlling for the effect of expressive vocabulary scores in Spanish (as measured by the

2

— .85*** .42*** .44*** .29*** .27*** .31*** .15* .46*** .36*** .35*** .21** .61*** 451.21 22.30

1

— .91*** .90*** .42*** .45*** .27*** .32*** .37*** .17* .49*** .44*** .30** .33*** .59*** 444.13 27.10 — .45*** .52*** .24* .42*** .43*** .30** .46*** .33*** .33*** .32*** .60*** 459.23 20.61

3

— .85*** .85*** .62*** .55*** .52*** .50*** .42*** .36*** .42*** .30*** 0.01 0.85

4

— .43*** .57*** .58*** .40*** .43*** .37*** .29*** .44*** .39*** 0.48 0.31

5

— .52*** .39*** .52*** .43*** .34*** .34*** .29*** .14 37.61 29.64

6

— .86*** .86*** .44*** .45*** .22* .50*** .15* 0.02 0.84

7

— .46*** .48*** .52*** .21* .52*** .21** 0.58 0.34

8

— .29** .28** .17 .36*** .05 43.83 27.55

9

— .79*** .77*** .38*** .20* 0.02 0.79

10

— .26*** .37*** .16 0.77 0.28

11

— .25** .13 45.59 27.83

12

— .05 51.00 6.24

13

— 1.76 1.55

14

Note. Expressive vocabulary scores are W scores. Compliance/executive control scores were created by averaging the child’s standardized percent correct score on Pencil Tap and standardized reversed latency to complete the Toy Sort. Scores for Pencil Tap are raw scores, and scores for Toy Sort are reversed latency to complete the sort. Exp Voc = expressive vocabulary. T1 = Time 1 (fall Year 1); T2 = Time 2 (spring Year 1); T3 = Time 3 (fall Year 2); C/EC = compliance/executive control. *p < .05. **p < .01. ***p < .001.

1. Exp voc—T1 2. Exp voc—T2 3. Exp voc—T3 4. C/EC—T1 5. Pencil Tap—T1 6. Toy Sort—T1 7. C/EC—T2 8. Pencil Tap—T2 9. Toy Sort—T2 10. C/EC—T3 11. Pencil Tap—T3 12. Toy Sort—T3 13. Child age 14. Income-to-needs M SD

Measure

Table 2 Correlations and Descriptive Statistics for the Full Sample

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Table 3 Model Fit Results for the Full Sample Model 1. No coupling 2. Unidirectional (Exp Voc ? C/EC) Difference between Model 2 and Model 3. Unidirectional (C/EC ? Exp Voc) Difference between Model 3 and Model 4. Bidirectional coupling Difference between Model 4 and Model Difference between Model 4 and Model

v2 (df)

CFI

RMSEA (CI)

SRMR

72.72 (24)*** 48.89 (22)***

0.94 0.97

0.09 (0.07, 0.11) 0.07 (0.04, 0.09)

0.05 0.03

59.54 (22)***

0.95

0.08 (0.06, 0.11)

0.05

36.80 (20)*

0.98

0.06 (0.02, 0.08)

0.03

1

v2diff ðdf Þa

23.19 (2)**

1

13.26 (2)**

2 3

11.76 (2)** 21.33 (2)**

Note. These models control for child age, gender, ethnicity, language status, income-to-needs ratio, and number of days between assessments. Whether the child was in a preschool or kindergarten classroom at the third assessment was also controlled for at Time 3 (T3). CFI = comparative fit index; RMSEA = root mean square error of approximation; SRMR = standardized root mean square residual; Exp Voc = expressive vocabulary; C/EC = compliance/executive control. a The chi-square difference test has been calculated using the Satorra–Bentler scaling correction factor in Mplus for analysis using full information maximum likelihood (Satorra & Bentler, 2001). *p < .05. **p < .01. ***p < .001.

Figure 1. Autoregressive cross-lagged model for the full sample, controlling for child age, gender, ethnicity, language status, incometo-needs ratio, and number of days between assessments at each time point. Whether the child was in a preschool or kindergarten classroom at the third assessment was also controlled for at T3. Regression coefficients can be interpreted as representing the amount of change in the outcome (in standard deviation units) that results from a 1 SD unit change in the predictor. A robustness check, to determine if missingness on expressive vocabulary and self-regulation impacted results, confirmed this model’s findings. Comparison across the four conditional cross-lagged models on a reduced sample of children (N = 176) confirmed the bidirectional coupling model as having the best model fit (comparative fit index = 0.98, root mean square error of approximation = 0.07, standardized root mean square residual = 0.02). There was consistency between the two models with the same significant and nonsignificant paths and minimal differences in the size of the coefficients. T1 = Time 1; T2 = Time 2; T3 = Time 3. *p < .05. **p < .01. ***p < .001.

Woodcock–Mu~ noz Picture Vocabulary subtest) on language scores in English and self-regulation scores across all time points. Chi-square difference tests calculated using the Satorra–Bentler scaling correction factor (Satorra & Bentler, 2001) indicated that the bidirectional model again had the best model fit (CFI = 0.95, RMSEA = 0.07, SRMR = 0.14). When examining the bidirectional model for the full sample as compared to a bidirectional model conducted on the DLL sample only while controlling for Spanish at all time points, there is consistency between the two. Paths show the same pattern of significance and nonsignificance, and there are minimal differences

in the size of the coefficients across the two models; see Figure 2.

Discussion Recognizing the importance of early vocabulary and self-regulation skills for school readiness and long-term academic success (Blair & Razza, 2007; Duncan et al., 2007), this study tested possible bidirectional influences between English language expressive vocabulary and self-regulation skills for monolingual and DLL children during preschool. Analyses were sensitive to the growing population

Bidirectionality in Self-Regulation and Vocabulary

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Figure 2. Autoregressive cross-lagged models for dual language learners (DLLs). Analysis examined the association between language competence in English and self-regulation in the DLL group while also accounting for language in Spanish. Models control for child age, gender, ethnicity, income-to-needs ratio, number of days between assessments at each time point, and Spanish expressive vocabulary. Whether the child was in a preschool or kindergarten classroom at the third assessment was also controlled for at T3. T1 = Time 1, T2 = Time 2, T3 = Time 3. **p < .01. ***p < .001.

of DLLs in U.S. classrooms (Hernandez et al., 2007), rather than assuming universal relations for all preschool populations. Using a cross-lagged model across three time points, we were able to examine the dynamic relations between these two skills over time and across subgroups. Based upon prior empirical evidence combined with a theoretical model that recognizes the interactive nature of skill development, we expected to find a bidirectional relation between children’s expressive vocabulary and self-regulation skills as demonstrated through their performance on compliance and executive control tasks. The results were supportive of our hypothesis, yielding evidence for bidirectionality between self-regulation and English expressive vocabulary skills in both monolinguals and DLLs. Bidirectionality Between Children’s Self-Regulation and English Expressive Vocabulary Using autoregressive cross-lagged models, study findings provided initial evidence for a bidirectional relation between self-regulation and English expressive vocabulary skills during preschool. Across all models (combined and subgroup analysis), evidence of a reciprocal relation between English expressive vocabulary and self-regulation skills emerged between T2 (spring Year 1) and T3 (fall Year 2). Thus, children who made more gains in self-regulation in the preschool year tended to make larger gains in expressive vocabulary from T2 to T3. Likewise, children who made more gains in expressive vocabulary during the preschool year also tended to make larger gains in self-regulation from T2 to T3. Although correlational, these findings are an indication that self-regulation and

expressive vocabulary might be contributing to development of one another. These findings are consistent with a model of development that views the growth of these skills as a coactive process that is iterative in nature (Fischer & Bidell, 2006). Both self-regulation and expressive vocabulary undergo rapid growth during the preschool period (Farkas & Beron, 2004; Kochanska et al., 2001; Pan et al., 2005). As children make gains in each of these skills across time, the degree to which each is called into service in the development of the other shifts over time. While there is long-standing theoretical support for the role of language in helping to regulate children’s behavior (Vygotsky, 1934/1986), the current study provides empirical support for that relation in the preschool years. Across all models, the association between vocabulary and later self-regulation emerges for children at T2 in the spring of Year 1. Researchers have theorized that the child’s internalization of a caregiver’s regulatory speech is facilitated by language development serving to proactively regulate behavior (Bernier et al., 2010). Preschool teachers often tell children to use their words in situations where they are unhappy or frustrated, modeling for children how to self-regulate through the use of language. Having spent the greater part of an academic year in a classroom being instructed on ways to use words to regulate actions, children may have internalized the message and are more readily engaging in private speech and internal verbal thought to regulate mental functioning (Berk & Winsler, 1995). Worth noting, the path from vocabulary to self-regulation between T2 and T3 is stronger than the pathway from self-regulation to vocabulary over this same

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time period. This finding is consistent with a model of development that emphasizes the interactive nature of developing skills and allows for variability in the strength of relations between skills at any given time point. Dynamic skill theory characterizes the interactions between skills as coactive where children develop along multiple strands simultaneously and skills in one strand influence developing skills in another (Fischer & Bidell, 2006). This characterization does not presuppose an equal influence between skills but makes room for variability in the degree of influence of one on the other across time. This theoretical framework also helps us understand the lack of significant association between expressive vocabulary at T1 and self-regulation at T2. Given the relatively low level of vocabulary development in the current sample (sample averages are below national norms), children’s limited expressive vocabulary, especially at T1, may explain the lack of significance found here. The present study uses expressive vocabulary as the measure of children’s language, operating under the assumption that it tells us something about children’s oral communication skills. The vocabulary that the children have at T1 may not yet be enough to function as private speech in the service of regulatory processes. Emergence of expressive vocabulary in predicting later self-regulation skills at T2 may reflect a tipping point in the amount of expressive vocabulary needed to facilitate self-regulation. As children’s ability to express themselves improves with increased vocabulary, they may be more able to call upon those skills and thereby exert regulatory control. Future work should explore whether a threshold—or certain level of expressive vocabulary skills—exists in the predictive relation between vocabulary and self-regulation both for monolinguals and DLLs. Self-Regulation as Early Predictor of English Expressive Vocabulary In addition to the reciprocal relation between skills that emerged between T2 (spring Year 1) and T3 (fall Year 2), self-regulation was also a significant predictor of English vocabulary skills between T1 (fall Year 1) and T2 (spring Year 1). Children with more self-regulation skills in the fall of Year 1 tended to make larger gains in expressive vocabulary over the course of the preschool year. This association was present in both the combined sample and the robustness test of the model for the DLL sample when controlling for Spanish expressive vocabulary. The influence of self-regulation skills on vocabulary development is well supported in the literature (e.g., McClelland et al.,

2007; Sektnan et al., 2010). The present findings suggest that self-regulation may be particularly important earlier in the preschool period for the acquisition and development of vocabulary skills. Conceptually, self-regulation skills help children to control thoughts and actions at will; doing so increases learning from the surrounding environment, which is essential in developing initial language skills (Blair, 2002; Bodrova & Leong, 2007). Importantly, selfregulation gains were predictive of continued gains in English expressive vocabulary from T2 to T3 consistent with extant literature suggesting a particularly strong association between self-regulation and the acquisition of the foundational language skills vital for early and long-term school achievement (Duncan et al., 2007). Patterns of Bidirectionality for Monolinguals and DLLs A strength of the current study was the use of multiple-group analysis to explore possible differences in the bidirectional associations between self-regulation and expressive vocabulary related to the linguistic exposure of the child—monolingual English speaking or DLL. Findings from the multigroup analysis suggested no difference in the pattern of relations between the groups. Although somewhat surprising given theoretical and empirical support for possible differences due to developmental context—in this case language exposure (Bialystok, 2001; Fischer & Bidell, 2006)—these findings speak to the generalizability of a reciprocal relation in preschool between vocabulary and self-regulation across linguistic groups. Much of the work finding differences in the development of self-regulatory abilities comes from research with bilingual populations (Bialystok et al., 2010) that have a greater degree of competence in each language than DLL populations. Moreover, DLLs in the current sample exhibited low expressive vocabulary skills in general, on average scoring below national norms. First, it is possible that a greater level of competency across two languages, or in language in general, is needed for differences to emerge. Additional investigation into possible differences in the pattern of associations between self-regulation and expressive vocabulary for bilingual populations is warranted in testing the generalizability of the findings. Second, further work must elucidate whether the patterns found in this study would also be evident between self-regulation and receptive vocabulary in DLLs. Since receptive vocabulary develops prior to expressive vocabulary (Benedict, 1979), the relation from receptive vocabulary to self-regulation might emerge earlier than in the present study.

Bidirectionality in Self-Regulation and Vocabulary

Limitations and Future Directions A strength of the present study is the longitudinal nature of the data across three time points, which has the potential to provide greater understanding of growth in self-regulation and expressive vocabulary and offer new insight into the possible reciprocal relation between these two processes. Although strengthened by the longitudinal nature of the study, these findings cannot be used to draw causal inferences given the correlational design. As such, we cannot know with certainty that these processes are actually contributing to the development of one another. It is quite possible that these processes are developing in unison, being linked by some other mechanism or third variable common to both. As an example, research on early language development has found some evidence for both domain-general (memory and representational competence) and domain-specific cognitive processes in the development of receptive and expressive vocabulary in early childhood (Rose, Feldman, & Jankowski, 2009). It is therefore possible that the relation between self-regulation and language observed here may reflect some underlying general cognitive ability rather than two coactive processes. As a first step toward exploring a reciprocal relation between children’s language and self-regulation skills, the current study focused on English language expressive vocabulary for both monolingual English speaking and DLLs. Educational experts and federal-level policy makers recognize the importance of bilingualism and home language maintenance (Office of Head Start—National Center for Cultural and Linguistic Responsiveness, n.d.). Although a policy shift is underway, there is still wide variability in the implementation of these practices and limited resources, including trained teachers, to support the development of English and the home language in the education system (Figueras-Daniel & Barnett, 2013). Given work suggesting the importance of English language development for academic success in the United States (Genesee et al., 2005), the central focus of the study is on English language development. We recognize this as both a strength and a potential weakness of the study. In conducting a robustness check of the model, controlling for Spanish expressive vocabulary in the DLL only group, the pattern of relations between self-regulation and English expressive vocabulary were held. Future work should examine bidirectionality between self-regulation and vocabulary skills in both Spanish and English to confirm that the pattern of associations that we see for DLLs

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emerges across both languages and therefore is a result of being exposed to two languages in the process of dual language acquisition. A third limitation to the study is the generalizability of the sample to all preschool children. Data for this study were collected from a single, large metropolitan area and should not be assumed to be representative of a national sample. The Hispanic population in the United States varies greatly, with regional differences often linked to country of origin. We know that the DLL children in this sample are Spanish speakers and that parents report speaking Spanish in the home, but we do not know about frequency or quality of the children’s home language context as contributors to their language development (Place & Hoff, 2011). We were also unable to account for their cultural background, immigration status, nativity status (generation), or family’s country of origin, all of which have been shown to be related to educational outcomes (e.g., De Feyter & Winsler, 2009). Additionally, children in the current study exhibited low expressive vocabulary skills in general. On average, children in the sample scored below national norms at all three time points. Future work should draw from a larger, nationally representative sample that takes into account the diversity of Hispanic and non-Hispanic preschool children in the United States. A somewhat unexpected finding was the autoregressive pathway for self-regulation as measured by compliance/executive control between T2 and T3 because it was nonsignificant. It is important to recognize that the bivariate correlation between T2 and T3 compliance/executive control is strong (Table 2). Thus, the lack of significance in the path between T2 and T3 self-regulation when modeled in this complex way suggests that T2 self-regulation is not predicting additional gains in self-regulation at T3 beyond what is already being accounted for by T1 self-regulation and T2 expressive vocabulary. Further examination of sample means reveals minimal change in compliance/executive control between these two time points. It is possible that not enough time has elapsed for a change in selfregulation to emerge. It also could be the case that the measure of self-regulation used in the current study is not sensitive enough to show change in this short time period. To further examine the apparent lack of change on average within the sample between T2 and T3, we explored the raw data for a possible ceiling effect. Examination of the means for the raw scores on the Pencil Tap task showed an increase in percent correct across the three time points. Examination of the means for the

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Toy Sort task showed a larger difference in the means between T1 and T2 than T2 and T3 (with little change in mean reversed latency to sort between the last two time points). Tests of skew and kurtosis were not significant for any of the three time points on these two variables. The lack of skew provides evidence against a classic ceiling effect; however, it may be that more children are performing at a higher level across the two tasks. This could result in reduced variability on the combined self-regulation score across individuals at T3. Despite this, the path between expressive vocabulary at T2 and self-regulation at T3 is significant. Thus, gains in children’s expressive vocabulary between T1 and T2 are related to the level of selfregulation at T3 for both monolinguals and DLLs. Future work is needed to confirm these relations using a wider array of self-regulation measures with greater differences in assessment periods. Relatedly, we recognize the complexity of selfregulatory processes and acknowledge disparities across the literature regarding the components constituting self-regulation. In the present study we draw upon a construct of self-regulation that incorporates the related processes of compliance and executive control. Although the operationalization of self-regulation through the use of tasks that require a combination of cognitive and behavioral control to inhibit behavioral responses and comply with adult demands is supported in the literature (e.g., McClelland et al., 2007; Smith-Donald et al., 2007), some may argue for a broader array of tasks, or alternative tasks, as more representative of selfregulation. In addition, language is assessed using a single measure of expressive vocabulary designed for monolingual populations rather than through multiple assessment tools that are normed with dual language populations. A fuller understanding of the reciprocal relation between self-regulation and language in the process of development would require a more comprehensive assessment of language. Given that this is the first study to directly test bidirectionality between children’s language and self-regulation with longitudinal data and to examine this relation within both monolingual and DLL populations, replication of the work is clearly needed to test the robustness of the model. Conclusion The preschool period is marked by profound growth in both self-regulation and vocabulary development, both of which predict later school success (Blair & Razza, 2007; Duncan et al., 2007; Farkas & Beron,

2004; Kochanska et al., 2001). As the first study that we know of to test a reciprocal relation between development in self-regulation and English expressive vocabulary across multiple assessment periods, current findings provide initial support for bidirectionality between these developing skills for both monolingual English speakers and DLLs. The results provide strong empirical support for vocabulary as a leading indicator of self-regulation skills in preschool. Findings also suggest that early self-regulation skills may play a particularly important role for vocabulary development. In addition to providing teachers with support for implementing content-focused early childhood curricula that promote vocabulary development, integration of clearly articulated preschool curricula that recognize and capitalize on the synergistic effects of self-regulation and expressive language during this period is an important direction for continued research. While recent interventions targeting self-regulation have demonstrated positive benefits for receptive vocabulary (e.g., the Chicago School Readiness Project; Raver et al., 2011), the present findings suggest that the development and experimental evaluation of such an intervention, if successful in improving children’s self-regulation, would likely also have a positive impact on children’s expressive vocabulary. Likewise, implementation of instructional strategies shown to foster vocabulary growth should positively impact developing self-regulation skills. Finally, the emergence of early self-regulation in predicting vocabulary development followed by a reciprocal relation between these skills in the preschool period, as seen here across both linguistic groups, speaks to the dynamic nature of skills development where developing skills influence one another and the nature of that influence changes over time.

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Bidirectionality in Self-Regulation and Expressive Vocabulary: Comparisons Between Monolingual and Dual Language Learners in Preschool.

Significant differences in language and self-regulation skills exist among children when they enter formal schooling. Contributing to these language d...
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