The roles of mathematical language and emergent literacy skills in the longitudinal prediction of specific early numeracy skills

Mathematical language (i.e., content-specific language used in mathematics) and emergent literacy skills predict children's broad numeracy development. However, little work has examined whether these domains predict development of individual numeracy skills (e.g., cardinality, number order). Thus, the aim of the current study was to examine longitudinal relations among mathematical language, emergent literacy skills, and specific early numeracy skills. Participants included 114 preschool children aged 3.12 to 5.26 years (M = 4.17 years, SD = 0.59). Specifically, this study examined whether mathematical language and three emergent literacy skills (print knowledge, phonological awareness, and general vocabulary) in the fall of preschool predicted 12 individual early numeracy skills in the spring, controlling for age, sex, rapid automatized naming, parent education, and autoregressors. Results indicated that mathematical language predicted development of most of the early numeracy skills (e.g., set comparison, numeral comparison, numeral identification), but findings for emergent literacy skills were not robust. Among the three emergent literacy skills, only print knowledge was a significant predictor of development in some specific numeracy skills, including verbal counting, number order, and story problems. Results highlight the important role of mathematical language in children's numeracy development and provide the foundation for future work in designing interventions to improve early numeracy skills.

Contributions of preschool behavioral self-regulation and social skills to growth in different domains of early math knowledge

The current study explored the relative contribution of individual differences in children's behavioral self-regulation and social skills (often referred to as learning-related skills) in the fall of preschool to children's rate of growth in different domains of early math knowledge through the spring of kindergarten. Participants were 684 children (Mage = 57.6 months, SD = 3.8, at Time 1 [fall of preschool]; 48% female; 43% Black, 32% White, 13% Latine, 11% multiracial, and 1% Asian). All children were from families with low incomes and lived in the midwestern United States. The math domains of informal numeracy, formal numeracy, and math language were assessed at four time points: fall and spring of preschool and fall and spring of kindergarten. Contrary to expectations, we did not find that either learning-related skill positively predicted rate of growth in math knowledge or observe differential relations by math domain. Rather, the relative contribution of behavioral self-regulation and social skills in the fall of preschool to rate of growth in math knowledge followed similar patterns across all math domains: an early advantage for children with higher initial social skills that stayed consistent over time (i.e., a nonsignificant slope effect) and an early advantage for children with higher initial behavioral self-regulation that diminished over time (i.e., a negative slope effect).

Early cumulative risk and outcomes in adolescence and adulthood: The role of executive function and behavioral regulation

This study examined the extent to which early cumulative risk predicts a range of behavioral and psychological outcomes (i.e., depression, future orientation, risky behavior, educational attainment, and socioeconomic outcomes) measured at ages 15 and 26 and whether executive function (EF) and/or behavioral regulation mediated and/or moderated these associations. Data for this study came from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development and included a sample of 1,364 participants (52% male) born in 1991 and followed through age 26. Results indicated that early cumulative risk was related to depression and risky behavior at age 15 as well as depression, income, future orientation, and educational attainment at age 26. Furthermore, both EF and behavioral regulation mediated relations among cumulative risk and academic achievement at age 15 and between cumulative risk and income and educational attainment at age 26. Finally, three significant interactions emerged for age 15 outcomes, indicating that EF and behavioral regulation may change relations between cumulative risk and depression, reading, and future orientation. Implications for future research are discussed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Corrigendum: Moving beyond dosage and adherence: a protocol for capturing dimensions of active child engagement as a measure of fidelity for social-emotional learning interventions

[This corrects the article DOI: 10.3389/fpsyg.2022.1014713.].

Factor structure of school readiness skills: conceptual vs. statistical distinctions

Introduction

School readiness skills are a broad set of abilities that children develop in early childhood that support achievement once they enter formal schooling. Three components of school readiness skills are of focus in the current study: executive function (EF), language/literacy, and mathematics. The current study examines to what extent 13 direct assessments of these skills statistically align with theoretical models for distinct construct- and timepoint-specific latent factors.

Methods

The sample included 684 children (52.34% male; 42% Black/African American; M_age = 4.80 years in the fall of prekindergarten) assessed in the fall and spring of the prekindergarten year.

Results

Factor analyses revealed the most statistical support for a model with a latent random intercept across timepoints and constructs, along with timepoint-specific latent factors in the fall and spring of prekindergarten (independent of the random intercept). The timepoint-specific latent factors primarily consisted of early literacy and mathematics assessments.

Discussion

These findings challenge commonly held practices of creating construct-specific latent factors in early childhood research and, to a lesser extent, timepoint-specific latent factors without consideration of the substantial shared variance across different constructs and timepoints. Implications for the factor structure and developmental theory of school readiness skills are considered, as well as practical considerations for future research.

The home numeracy environment and children's math skills: The moderating role of parents' math anxiety

Evidence suggests that parents' math anxiety moderates the association between parents' help in mathematics homework and first graders' mathematics skills. Understanding whether similar associations are evident in younger children, in regard to the home numeracy environment (HNE) is essential, given that early math skills are strong predictors of later academic outcomes, and children's skills prior to kindergarten are fostered principally by their parents. Thus, the purpose of this study was to examine the association and interaction between the HNE and parents' math anxiety related to preschool children's numeracy performance. Participants were 121 parent-child dyads. Results from hierarchical multiple regression models demonstrated that parents' math anxiety and the HNE, included as separate predictors of children's math skills, were not statistically significant. However, the interaction between HNE and parents' math anxiety was statistically significant, such that the positive association between HNE and children's numeracy skills emerged when parents felt less anxious about math. These findings highlight the importance of accounting for parents' math anxiety when exploring the home influences on children's numeracy skills.

Moving beyond dosage and adherence: A protocol for capturing dimensions of active child engagement as a measure of fidelity for social-emotional learning interventions

Social-emotional competencies are important for school-readiness and can be supported through social-emotional learning (SEL) interventions in the preschool years. However, past research has demonstrated mixed efficacy of early SEL interventions across varied samples, highlighting a need to unpack the black box of which early interventions work, under what conditions, and for whom. In the present article we discuss the critical implementation component of active child engagement in an intervention as a potential point of disconnect between the intervention as designed and as implemented. Children who are physically present but unengaged during an intervention may lead to decreased average impacts of an intervention. Furthermore, measuring young children's active engagement with an intervention may help to guide iterative intervention development. We propose a four-step protocol for capturing the multi-dimensional and varied construct of active child engagement in a SEL intervention. To illustrate the utility of the protocol, we apply it to data from a pilot study of a researcher-implemented, semi-structured block play intervention focused on supporting the development of SEL and math skills in preschoolers. We then present future directions for the integration of active participant engagement into the measurement of implementation of SEL interventions for young children.

Home science interactions and their relation to children's science core knowledge in preschool

A limited body of work has examined the nature and scope of young children's science-related activities outside of the school context, and thus there is little understanding or consensus regarding what comprises the home science environment (HSE; e.g., interactions, activities, resources) and how specific factors of the HSE relate to children's science performance. The two primary goals of this study were to (a) examine the factor structure of a parent-report measure of home science interactions and (b) evaluate how these factors relate to the science core knowledge of young children from families with low incomes. A total of 125 families with children aged 3 to 5 years (52 girls) participated in the study. Children were assessed on a measure of science core knowledge, and parents completed a brief questionnaire on their home science interactions that included questions pertaining to both home science disciplinary core idea (DCI) engagement and home science and engineering practice (SEP) engagement. Findings revealed that although separating home science interactions into distinct DCI and SEP factors represented the data well, the best overall representation of home science interactions was a one-factor model that included only home DCI engagement items. In addition, home DCI engagement was significantly predictive of children's science core knowledge over and above a large group of covariates, including children's age, race/ethnicity, sex, and performance on math, executive function, and vocabulary tasks as well as their parents' education.

Examining longitudinal associations between internalizing problems, body mass index, and language during childhood

The current study examines the extent to which associations between internalizing problems, body mass index (BMI), and language skills from early (36 months) to late childhood (fifth grade) are due to relatively stable between-child differences, time-specific correlations, or cross-lagged paths. Data from the NICHD study, Early Child Care and Youth Development (N = 1,364) were used. Results showed that internalizing problems and language are significantly and negatively correlated due to relatively stable between-child differences, with some evidence of positive cross-lagged paths, where better language at 36 months, 54 months, and third grade predicted more internalizing problems at the subsequent timepoint, and more internalizing problems at third grade predicted better language at fifth grade. Time-specific associations for BMI showed a negative correlation with language at 36 months and a positive correlation with internalizing problems at 54 months only. Additionally, higher internalizing at third grade predicted higher BMI at fifth grade, though the association was small and no other cross-lagged paths between internalizing and BMI emerged. These findings suggest that previous research documenting cross-lagged associations between BMI and internalizing problems, and between language and internalizing problems may be biased due to between child differences not fully controlled for in prior models. Implications for understanding these key aspects of youth's healthy development are considered. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Examining Associations Between Food Insecurity, Inhibitory Control, and Body Mass Index in Preschoolers

OBJECTIVE

This study examines relations between food insecurity, inhibitory control, and body mass index (BMI) in early childhood.

METHOD

The sample comes from an evaluation of a state-funded prekindergarten program and includes 126 children (mean age = 4.73 yrs, female = 42%) from families with low incomes. Parents reported on their child's food insecurity. Child inhibitory control was assessed using a performance-based task, and children's height and weight were objectively collected at the same time as the inhibitory control assessment. A regression model was used to test whether inhibitory control moderated the association between food insecurity and BMI. The model included a large battery of covariates and adjusted for clustering at the classroom level. Ad hoc analyses were conducted to examine the robustness of findings to different conceptualizations of food insecurity based on the US Department of Agriculture's categories for severity.

RESULTS

A significant interaction revealed that inhibitory control moderated the association between food insecurity and children's BMI percentile. Investigation of the simple slopes suggested that greater food insecurity was related to a higher BMI percentile among children who demonstrated stronger inhibitory control. In addition, results from ad hoc analyses examining categories of food insecurity indicated that experiencing very low food security was also related to a higher BMI among children with average and strong inhibitory control.

CONCLUSION

This study makes a unique contribution to the existing literature by examining relations among food insecurity, inhibitory control, and BMI during a critical period in children's physical and brain development. Findings have implications for public health efforts to address childhood obesity among populations with low incomes.

Self-Regulation in Preschool: Examining Its Factor Structure and Associations With Pre-academic Skills and Social-Emotional Competence

Self-regulation in early childhood is an important predictor of success across a variety of indicators in life, including health, well-being, and earnings. Although conceptually self-regulation has been defined as multifaceted, previous research has not investigated whether there is conceptual and empirical overlap between the factors that comprise self-regulation or if they are distinct. In this study, using a bifactor model, we tested the shared and unique variance among self-regulation constructs and prediction to pre-academic and social-emotional skills. The sample included 932 preschool children (Mage = 48 months, SD = 6.55; 49% female), their parents, and their teachers in the United States. Children’s self-regulation was assessed using measures of executive function, behavioral self-regulation, and emotion regulation. The bifactor model demonstrated a common overarching self-regulation factor, as well as distinct executive function and emotion regulation factors. The common overarching self-regulation factor and executive function predicted children’s pre-academic (i.e., mathematics and literacy) and social-emotional skills. The emotion regulation factor predicted children’s social-emotional skills. Identifying the shared and unique aspects of self-regulation may have important implications for supporting children’s regulatory skills as well as their success in school.

Conceptualizing the factor structure of parents' math anxiety and associations with children's mathematics skills

There is a growing literature examining the association between parents' math anxiety and children's mathematics skills. Previous research has considered parents' math anxiety as a unidimensional construct that primarily focused on parents' experiences doing mathematics themselves. However, this research did not account for parents' experiences when doing mathematics with their children. Thus, there were two goals of the present study: (1) to identify the structure of parents' math anxiety when considering context-dependent situations, and (2) to determine whether parental math anxiety was related to children's early numeracy skills. We conducted a series of confirmatory factor analyses using a sample of 155 preschool children (M_age  = 4.20 years, SD = 0.71; 51% female). The best fitting model of parents' math anxiety was a bifactor model, suggesting that parents' math anxiety was best conceptualized as a multidimensional construct. However, structural equation models showed parent math anxiety was not a significant predictor of children's numeracy performance. These findings provide a foundation for understanding parents' math anxiety as multidimensional and raise questions about potential mechanisms that may explain prior work finding mixed relations between math anxiety and children's numeracy performance.

Examining transactional relations between behavioral self-regulation and social-emotional functioning during the transition to kindergarten

The present study examined longitudinal associations between behavioral self-regulation and social-emotional functioning across four waves of measurement during the transition from preschool to kindergarten in a low-income sample. Participants included two cohorts of children (N = 558; 51% male). Children in both cohorts were 4 years old (Cohort 1: M = 4.82 years, SD = .31; Cohort 2: M = 4.80 years, SD = .31). Forty-four percent of children were Black, 32% were White, 13% were Latino, 10% were Multiracial, and 1% were Asian. Monthly income ranged from $0-5,539 (M = $1,508.18, SD = $892.92). Two statistical methods were used to examine relations among constructs. The cross-lagged panel model revealed a mixed pattern of relations between behavioral self-regulation and two indicators of social-emotional functioning (social skills and behavior problems) over time. There were no significant relations among behavioral self-regulation and social-emotional functioning during the preschool year; however, evidence for bidirectional associations were found between the spring of preschool and the fall of kindergarten. There were no significant relations among behavioral self-regulation and behavior problems at any time point. Finally, there were bidirectional relations among social skills and behavior problems in preschool, but directional relations emerged after this time point. A second model that included random intercepts was also run with the cross-lagged paths. Results from this model indicated that the random intercepts between behavioral self-regulation, social skills, and behavior problems were significantly related. Implications for future research are discussed. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Examining Additive and Synergistic Relations Between Preschool Self-Regulation and Executive Function Skills: Predictions to Academic Outcomes

In the present study, we examined the extent to which teacher-rated self-regulation and directly assessed executive function skills were independently, additively, or synergistically related to academic achievement during the transition to kindergarten. The sample included 126 children (42% female; M_age = 4.73 years) from families with low incomes who participated in a larger evaluation of state-funded preschool. Regression models with children nested in their respective preschool classrooms investigated main effects and moderated effects of teacher-rated self-regulation skills manifested in preschool classroom behaviors and cognitive executive function skills assessed through direct assessments on math, literacy, and vocabulary in the spring of preschool and in the fall of kindergarten. Results revealed independent but not additive relations between executive function and math in the spring of preschool and self-regulation and literacy in the fall of kindergarten. One significant interaction emerged providing evidence for synergistic relations between teacher-rated self-regulation and directly assessed executive function for literacy at both timepoints across the transition to kindergarten. Implications for policy and practice are discussed.

Parents' math anxiety and mathematics performance of pre-kindergarten children

Prior research demonstrates that individuals' math anxiety may be negatively related to their mathematics performance. However, little research has examined how caregivers' math anxiety is associated with children's mathematics performance prior to kindergarten. The purpose of this study was to investigate the relation between parents' math anxiety and the change in children's mathematics performance during the preschool year. Participants were 310 preschool-age children (155 female; 4.12-5.78 years of age, M = 5.20 years, SD = 0.29). Structural equation modeling results demonstrated that parents' math anxiety was significantly negatively related to change in children's mathematics performance during the pre-kindergarten year when controlling for fall mathematics performance and demographics. Moreover, multigroup path analyses revealed that this association did not differ for male versus female children.

Pilot Intervention Enhances Preschoolers' Self-Regulation and Food Liking

OBJECTIVE

The goal of this study was to develop and evaluate a 5-week intervention that targeted self-regulation and healthy food liking through mindfulness and classroom-based games with exposure to fruits and vegetables.

METHODS

Children (mean age, 3.6 ± 0.05 years) in 1 Head Start center received the classroom-based intervention (n = 24) and children in a second did not (n = 15). Assessments of self-regulation and liking of fruits and vegetables were administered pre- and postintervention.

RESULTS

Children in the intervention, but not the comparison group, experienced significant improvements in behavioral regulation (P = 0.003) and liking of fruits and vegetables (P = 0.02).

CONCLUSIONS AND IMPLICATIONS

This study lays a foundation for future research that replicates findings with a larger sample using a randomized controlled design, incorporates more typical mindful eating practices, and includes additional, broader measures of food liking.

Examining the Factor Structure of the Home Mathematics Environment to Delineate Its Role in Predicting Preschool Numeracy, Mathematical Language, and Spatial Skills

A growing body of evidence suggests that the ways in which parents and preschool children interact in terms of home-based mathematics activities (i.e., the home mathematics environment; HME) is related to children's mathematics development (e.g., primarily numeracy skills and spatial skills); however, this body of evidence is mixed with some research supporting the relation and others finding null effects. Importantly, few studies have explicitly examined the factor structure of the HME and contrasted multiple hypothesized models. To develop more precise models of how the HME supports children's mathematics development, the structure of the HME needs to be examined and linked to mathematics performance. The purpose of this study was to extend prior work by replicating the factor structure of the HME (as one general HME factor and three specific factors of direct numeracy, indirect numeracy, and spatial) and using those factors to predict direct assessments of children's numeracy, mathematical language, and spatial skills. It was hypothesized that the general HME factor would be related to each direct assessment, the direct numeracy factor would be related to both numeracy and mathematical language, and the spatial factor would be related to spatial skills. Using a sample of 129 preschool children (M age = 4.71 years, SD = 0.55; 46.5% female), a series of confirmatory factor analyses were conducted. Results diverged somewhat from prior work as the best fitting model was a bifactor model with a general HME factor and two specific factors (one that combined direct and indirect numeracy activities and another of spatial activities) rather than three specific factors as had previously been found. Further, structural equation modeling analyses suggested that, in contrast to expectations, only the direct + indirect numeracy factor was a significant predictor of direct child assessments when accounting for age, sex, and parental education. These findings provide evidence that a bifactor model is important in understanding the structure of the HME, but only one specific factor is related to children's outcomes. Delineating the structure of the HME, and how specific facets of the HME relate to children's mathematics skills, provides a strong foundation for understanding and enhancing the mechanisms that support mathematics development.

Parental restrictive feeding with Latinx adolescents: Examining the role of adolescent effortful control

The objective of this study was to test if youth effortful control, a general process of self-regulation that is rooted in temperament, uniquely predicts maternal restrictive feeding with Latinx adolescents above and beyond demographic/contextual factors, prior use of restrictive feeding, and common markers of obesity-proneness. The study sample consisted of Latinx fifth and sixth graders and their mothers residing in the Midwestern U.S. (N =  97 dyads). Effortful control, maternal restrictive feeding, demographic/contextual factors, and markers of obesity proneness were measured across two waves of data collection approximately one year apart. Results demonstrated an inverse relation between effortful control and maternal restrictive feeding after controlling for Time 1 demographic/contextual factors, maternal BMI, maternal restrictive feeding, youth BMI z-score, and perceived youth weight. Future directions include testing for the presence of an ironic feedback process such that Latinx mothers' attempts to overcome deficits in their children's self-regulation skills through restrictive feeding may be inadvertently maintaining the problem.

Red Light, Purple Light! Results of an Intervention to Promote School Readiness for Children From Low-Income Backgrounds

Considerable research has examined interventions that facilitate school readiness skills in young children. One intervention, Red Light, Purple Light Circle Time Games (RLPL; Tominey and McClelland, 2011; Schmitt et al., 2015), includes music and movement games that aim to foster self-regulation skills. The present study (N = 157) focused on children from families with low-income and compared the RLPL intervention (SR) to a revised version of RLPL that included literacy and math content (SR+) and a Business-As-Usual (BAU) control group. In both versions of the intervention, teachers were trained to administer the self-regulation intervention in preschool classrooms with coaching support. Although not statistically significant, children receiving either version of the intervention gained more in self-regulation on the Head-Toes-Knees-Shoulders (HTKS) over the preschool year compared to the BAU group (β = 0.09, p = 0.082, Cohen's d = 0.31). Effect sizes were similar to previous studies (Schmitt et al., 2015; Duncan et al., 2018) and translated to a 21% difference in self-regulation over and above the BAU group at post-test. Furthermore, children participating in either version of the intervention gained significantly more in math across the school year compared to children in the BAU group (β = 0.14; p = 0.003, Cohen's d = 0.38), which translated to a 24% difference in math over and above the BAU group at post-test. Results were somewhat stronger for the SR+ version, although effect sizes across intervention conditions were comparable. There were no statistically significant differences across groups for literacy skills. Results extend previous research and suggest that the RLPL intervention, which includes an explicit focus on self-regulation through music and movement games, may improve children's self-regulation and math scores over the preschool year.

Additive and synergistic relations of early mother-child and caregiver-child interactions for predicting later achievement

This study examines associations between stimulating-responsive social interactions with mothers and nonparental childcare providers during the first 3 years of life and children's vocabulary and mathematics skills through age 15 (N = 1,364). Additive relations were found in which more stimulating-responsive interactions with mothers and with caregivers were linked to higher mathematics achievement in childhood and adolescence. More stimulating-responsive early interactions with mothers were also associated with larger child vocabularies through age 15. Synergistic relations, consistent with the dual-risk hypothesis, also were found. Children whose early interactions with both mothers and caregivers were low in stimulation and responsivity had substantially lower mathematics skills. Implications for early childhood interventions and policies are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Exploring cross-cultural variations in the development of executive function for preschoolers from low and high socioeconomic families

This study investigated cross-cultural variation in the development of executive functioning (EF) across the preschool period for United States and Chinese children from low and high socioeconomic families using a longitudinal design. Participants included 216 preschool children ( n = 125 from the US; n = 91 from Shanghai and Jiangxi, China). On average, children were approximately 4 years old. In the US sample, 56% were female, and in the Chinese sample, 54% were female. Results from multi-level models varied slightly with regard to specific EF domains, but generally indicated that Chinese children experienced greater gains in EF during the preschool period compared to US children. Cross-cultural differences in EF growth did not vary by socioeconomic status. These findings highlight cultural variability in the development of EF and provide a foundation for additional research exploring factors that may help explain differential growth in EF for Chinese children compared to US children during the preschool period.

Combining a Kindergarten Readiness Summer Program with a Self-Regulation Intervention Improves School Readiness

Self-regulation and academic skills in kindergarten are strong predictors of later achievement. However, many children enter kindergarten without adequate levels of these skills, often because of limited participation in early childhood education. The current study examined a kindergarten readiness summer program (Bridge to Kindergarten; B2K) that served children with no prior preschool experience. The first study goal was to examine the effects of adding a self-regulation intervention to the B2K program on children's self-regulation, math, and literacy. The second study goal was to compare changes in self-regulation, math, and literacy during the kindergarten transition period for children attending the B2K program with the intervention to expected development. Results from a randomized trial indicated that children who participated in the B2K program that included the self-regulation intervention experienced more gains in self-regulation relative to children who participated in the B2K program alone. There were no significant effects on math or literacy at the end of the program. However, when examining change during the kindergarten transition period, participation in the B2K program with the self-regulation intervention was associated with improved growth in self-regulation, math, and literacy into the fall of kindergarten compared to expected development. Collectively, the findings suggest a kindergarten readiness summer program that incorporates a self-regulation intervention leads to improved school readiness in children at higher risk for later school difficulties.

Evaluating the predictive validity of the computerized comprehension task: comprehension predicts production

Until recently, the challenges inherent in measuring comprehension have impeded our ability to predict the course of language acquisition. The present research reports on a longitudinal assessment of the convergent and predictive validity of the MacArthur-Bates Communicative Development Inventories: Words and Gestures (CDI: WG; Fenson et al., 1994, 1993, 2007) and the Computerized Comprehension Task (CCT; Friend & Keplinger, 2003, 2008). The CDI: WG and the CCT evinced good convergent validity; however, the CCT better predicted subsequent parent reports of language production. Language sample data in the 3rd year confirm this finding: The CCT accounted for 24% of the variance in unique word use. These studies provide evidence for the utility of a behavior-based approach to predicting the course of language acquisition into production.

A Longitudinal Assessment of the Home Literacy Environment and Early Language

This longitudinal assessment concentrated on the relation between the Home Literacy Environment (HLE) and early language acquisition during infancy and toddlerhood. In Study 1, after controlling for SES, a broadly-defined HLE predicted language comprehension in 50 infants. In Study 2, 27 children and their primary caregivers returned for further analyses. Findings revealed that the HLE measured in infancy predicted language production in toddlerhood, and maternal redirecting behaviors measured in toddlerhood were negatively associated with expressive language. Results across both studies indicate the importance of a broadly-defined HLE (including joint attention and parent-child conversation) for language development. Taken together, these findings highlight the importance of the HLE in supporting both receptive and expressive vocabulary growth in the second and third years of life.

Use of pulsed field gel electrophoresis to differentiate Coxiella burnetii strains

Pulsed field gradient gel electrophoresis (PFGE) provides a powerful technique for the analysis of bacterial genomic DNA by allowing the resolution of DNA fragments as large as 9000 kilobase pairs (kbp). When isolates of Coxiella burnetii were examined using this method, the restriction enzymes Not I and Sfi I gave the fewest and most easily resolved fragments. Sfi I cuts the genome of the Priscilla isolate of C. burnetii into 15 DNA fragments ranging in size from 320 to 18 kbp, and Not I cuts the DNA of this isolate into 20 fragments from 293 to 10 kbp in size. Analysis of the undigested DNA and summing of the Sfi I restriction fragments both indicate that the C. burnetii DNA contains approximately 1600 kbp, or is about one-third the size of the DNA in Escherichia coli. Comparisons of isolates revealed that the numbers and patterns of DNA fragments observed correlate with proposed strain designations. Because PFGE allows the reproducible separation of restriction endonuclease-digested C. burnetii DNA fragments into precise bands, it greatly facilitates the selection of large DNA fragments for cloning. Bands harvested from the gel can be cloned. Clone banks are invaluable for identifying the location of specific genes and landmarks and providing material for future experiments, including DNA sequencing. Yeast artificial chromosome (YAC) cloning vectors can accept fragments as large as 500 kbp. The fragmentation patterns of C. burnetii that we have obtained with infrequent-cutting enzymes are small enough to be cloned into YAC vectors. Using a PFGE selection method means that only small libraries would have to be created and screened. Thus, the results of these experiments also demonstrate the applicability of PFGE for deriving a physical map of C. burnetii chromosomal DNA. Development of such a macrorestriction map will facilitate genetic and molecular studies with C. burnetii.