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Are There Long-Term Effects of Early Child Care?

Jay Belsky Birkbeck University of London

Deborah Lowe Vandell University of California, Irvine

Margaret Burchinal University of North Carolina, Chapel Hill

K. Alison Clarke-Stewart University of California, Irvine

Kathleen McCartney Harvard University

Margaret Tresch Owen The University of Texas, Dallas

The NICHD Early Child Care Research Network

Effects of early child care on children’s functioning from 41 2

years through the end of 6th grade (M age 5 12.0 years) were examined in the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development (n 5 1,364). The results indicated that although parenting was a stronger and more consistent predictor of children’s development than early child-care experience, higher quality care predicted higher vocabulary scores and more exposure to center care predicted more teacher-reported externalizing problems. Discussion focuses on mechanisms responsible for these effects, the potential collective consequences of small child-care effects, and the importance of the ongoing follow-up at age 15.

Large numbers of children in the United States ex- perience routine nonmaternal child care during their infant, toddler, and preschool years. In 1999, 9.8 million American children under the age of five years were in child care for 40 or more hours a week (Committee on Family and Work Policies, 2003), with many beginning in the first year of life (U.S. Bureau of the Census, 1999). Questions about possible long- term effects of early child care on school-aged

children’s functioning are of great interest to parents, educators, and policymakers, especially as heated debate has often characterized discussion of child- care effectsFboth before the onset of the work pre- sented in this article (e.g., Belsky, 1986, 1988; Clarke- Stewart, 1989; Fox & Fein, 1990; Phillips, McCartney, Scarr, & Howes, 1987) and more recently (e.g., Bel- sky, 2001; Crockenberg, 2003; Greenspan, 2003; Langlois & Liben, 2003; Maccoby & Lewis, 2003; NICHD Early Child Care Research Network [ECCRN], 2003a). To be clear, in all discussion that follows, the language of child-care ‘‘effects’’ refers to statistical associations discerned in field studies be- tween measurements of child-care experience and child development, typically after controlling for confounding variables. Widely appreciated by the authors of this report and investigators in the field is that such correlational research does not allow strong inferences regarding causation as efforts to control confounding factors can never insure that all important ‘‘third variables’’ or alternative explan- ations have been taken into account. Although ef- forts are made in this paper to avoid causal language, whenever the term ‘‘effects’’ is used to describe results it refers to statistical effects of child- care predictor variables in this and related nonex- perimental field studies.

This study is directed by a steering committee and supported by NICHD through a cooperative agreement (U10) that calls for a scientific collaboration between the grantees and NICHD staff. Participating investigators on the NICHD Early Child Care Re- search Network, listed in alphabetical order, are: Jay Belsky, Birkbeck University of London; Cathryn Booth-LaForce, Univer- sity of Washington; Robert Bradley, University of Arkansas, Little Rock; Margaret Burchinal, University of North Carolina, Chapel Hill; Susan B. Campbell, University of Pittsburgh; K. Alison Clarke-Stewart, University of California, Irvine; Sarah L. Fried- man, Institute for Public Research, CAN Corporation, Alexandria, Virginia, Maryland; Kathryn Hirsh-Pasek, Temple University; Aletha Huston, University of Texas, Austin; Kathleen McCartney, Harvard University; Marion O’Brien, University of North Caro- lina, Greensboro; Margaret Tresch Owen, University of Texas, Dallas; Robert Pianta, University of Virginia; and Susan Spieker, University of Washington; Deborah Lowe Vandell, University of California, Irvine.

Correspondence concerning this article should be addressed to Jay Belsky, Institute for the Study of Children, Families and Social Issues, Birkbeck University of London, 7 Bedford Square, London WC1B 3RA, UK. Electronic mail may be sent to [email protected].

Child Development, March/April 2007, Volume 78, Number 2, Pages 681 – 701

Two issues have been central to the debate about child-care ‘‘effects,’’ one pertaining to the specificity of effects and the other to the endurance of effects. Some have highlighted potentially beneficial consequences of early child care, especially of high-quality care, on social functioning (e.g., Howes, 1988; Peisner- Feinberg & Burchinal, 1997; Vandell, Henderson, & Wilson, 1988), as well as on cognitive-linguistic de- velopment or academic achievement (e.g., Broberg, Wessels, Lamb, & Hwang, 1997; Burchinal et al., 2000; Peisner-Feinberg et al., 2001), particularly in the case of economically disadvantaged children at- tending high-quality early-intervention programs (e.g., Campbell et al., 2001; Reynolds, 2000; Sch- weinhart, Weikart, & Larner, 1986). Others have called attention to potentially adverse consequences, especially of long hours of care initiated early in life, on socioemotional functioning, including behavior problems (e.g., Bates et al., 1994; Belsky, 1990, 2001; Haskins, 1985; Vandell & Corasaniti, 1990). More- over, some have contended that child-care ‘‘effects,’’ whether beneficial or detrimental, do not endure beyond the preschool or early elementary school years (e.g., Blau, 1999; Colwell, Pettit, Meece, Bates, & Dodge, 2001; Deater-Deckard, Pinkerton, & Scarr, 1996; Egeland & Hiester, 1995), whereas others have claimed that child-care ‘‘effects’’ are more long last- ing (e.g., Belsky, 1988; Vandell et al., 1988; Vandell & Corasaniti, 1990) or endure for some time, at least in the case of low-income children in high-quality care (Campbell et al., 2001; Lazar & Darlington, 1982; Schweinhart et al., 1986).

The National Institute of Child Health and Hu- man Development (NICHD) Study of Early Child Care and Youth Development (SECCYD), launched in the early 1990s, was designed to address these issues while overcoming many of the design limita- tions of prior work (NICHD ECCRN, 2005a). One of the foremost limitations was the inability of most previous research to distinguish and thereby disen- tangle potentially distinctive (statistical) effects of different features of the child-care experience, par- ticularly the quality of the care, the amount or quan- tity of care, and the type of care. Virtually all research before the NICHD SECCYDFand some more recent work as well (e.g., Bacharach & Baumeister, 2003; Borge, Rutter, Cote, & Tremblay, 2004)Fexamined one or another feature of the child-care experience, but never all three.

At the initiation of the NICHD SECCYD, the collaborating investigators engaged in extensive discussion about how to define ‘‘child care’’ oper- ationally in order to address relations between vari- ation in these aspects of the early child-care

experience and child development. Especially be- cause definition would affect which child care ar- rangements wereFand were notFstudied, the decision was made to define child care broadly, such that any and all nonmaternal care that was regularly scheduled for at least 10 hr per week qualified as ‘‘child care,’’ including care by fathers, grandparents, and other relatives. Ultimately, the decision was made to be inclusive because of a desire not to privilege the biological relatedness of the caregiver or the location of the care in the sense that certain arrangements would not qualify as child care. Whereas some might contend, not unreasonably, that nonmaternal care provided by the father or by the grandmother should not be regarded as child care, it seemed questionable that care provided by a grandmother in her own home was somehow less ‘‘child care’’ than was care provided by a nanny living full time in the child’s home or by a babysitter who came to the child’s home to provide care, es- pecially from the perspective of the infant receiving the care.

In prior published work, the NICHD ECCRN (2002, 2003a, 2003b, 2004a, 2004b, 2004c, 2005a) re- ported that all three of the aforementioned core features of early child careFquality, quantity, and typeFwere related to children’s school readiness and social behavior measured at age 41

2 years, just

before the transition to school. Higher quality child care predicted higher levels of preacademic skills and language performance, although not social functioning, whereas more hours in care and in- creasing hours in care predicted higher levels of behavior problems, but not academic skills or lan- guage functioning. Intriguingly, greater exposure to center-type care proved to be related to child func- tioning in both positive and negative ways, pre- dicting better language skills and performance on a memory task, but also more problem behaviors (see also NICHD ECCRN, 2004a, 2004b, 2004c, 2006). These associations between experience in child care and child development were reliable, albeit small by most standards. Nevertheless, there is great interest in the potential long-term sequelae of child-care ex- perience for many reasons, including the fact that extensive early child care is a relatively new experi- ence for children in our culture, coupled with the fact that child-care experience is now normative for U.S. children.

When children in the NICHD SECCYD were fol- lowed-up through third grade (� 8 years), some of the ‘‘effects’’ detected at 54 months endured, some disappeared, and others emerged for the first time (NICHD ECCRN, 2005b). More specifically, higher

682 Belsky et al.

quality care continued to be linked to higher scores on standardized tests of math, memory, and vo- cabulary skills. More time spent in child care no longer predicted externalizing behavior problems, but in contrast to findings at 54 months, was asso- ciated with lower social competence and poorer academic work habits, the latter being an outcome of child care examined for the first time when children were in third grade. Finally, more time periods of center care continued to relate to children’s devel- opment in both positive and negative ways, being associated with better memory, but also with more conflicted relationships with teachers and mothers. As before, then, the third-grade follow-up high- lighted the relative independence of quality, quan- tity, and type of child care in relation to children’s development.

The purpose of the current study is to extend our ongoing research linking early child-care experience with child functioning through sixth grade, in order to determine whether the earlier detected associ- ations involving the quality, quantity, and type of care change over time. To our knowledge, the only other investigations that have involved such long- term evaluations of samples first studied in infancy were carried out in Sweden, where the ecology of child care is markedly different from the United States (e.g., better paid staff, less staff turnover, higher quality care; Andersson, 1992; Broberg et al., 1997) or, in the United States, involved children en- rolled in a particular high-quality, center-based, early-intervention programs intended to compensate for disadvantages in the home (e.g., Campbell et al., 2001; Lazar & Darlington, 1982; Reynolds, 2000). As a result, the work reported here breaks new ground by tracking American children to ages 11 – 12 and examining how variation in the type, quality, and quantity of care of the kind typically experienced in communities across this country is associated with cognitive development, achievement, and socio- emotional functioning.

The NICHD SECCYD is well suited to address issues of the long-term correlates of child-care ex- perience because information about child-care use was collected every 3 – 4 months from the time in- fants were 1 month of age until school entry. Quality of the children’s primary child-care setting (e.g., center, family day-care home, nanny in own home) was assessed using specially developed observa- tional methods when children were 6, 15, 24, 36, and 54 months of age. Measures of cognitive and social functioning were collected longitudinally at 41

2 years

and in first, third, fifth, and sixth grade (and, for some measures, also in kindergarten, second, and

fourth grade). With these longitudinal assessments, we are positioned to determine whether findings pertaining to the quality, quantity, and type of child care detected at age 41

2 years are maintained, in-

crease, or decrease across the first 7 years of school (i.e., K – 6) in a relatively large and diverse sample. We also consider the possibility that previously un- detected associations involving child care and child development may emerge. Not only is it the case that some linkages between child care and child devel- opment (i.e., quantity:problem behavior) that were evident in the NICHD SECC at one age (i.e., 24 months) and disappeared at a later age (i.e., 36 months) reappeared thereafter (i.e., 54 months), but others, too, have detected significant child-care findings at a later age that were not present earlier (i.e., Broberg et al., 1997).

In all nonexperimental studies of child care, se- lection bias is an issue because family and child characteristics are related to child outcomes as well as the type, amount, and quality of care children experience (Committee on Family and Work Policies, 2003). To reduce this problem, relations between child-care experience and child development are tested in the current study after controlling for an extensive array of family factors. A related concern is that associations between child care and child func- tioning may be explained by subsequent experien- ces. In the case of school-aged children, concurrent experiences at home and in school, or the amount of time spent in an afterschool program, may account for developmental trajectories during the primary grades, rather than children’s earlier child-care his- tories. For example, quality of classroom instruction in the primary grades may eliminate earlier associ- ations linking child-care quality with children’s cognitive-linguistic development. Additionally, large amounts of after-school care during the primary grades may account for behavior problems in the primary grades rather than earlier child-care hours or experience of center-based care. Consequently, in the current study, measures of the quality of early and concurrent parenting, of the quality of classroom instruction in the primary grades, and of the amount of out-of-school care in the primary grades were also included as covariates.

Recently, van IJzendoorn et al. (2004) carried out a re-analysis of data from the NICHD SECCYD linking a large amount of time spent in care with higher externalizing problem scores at 54 months of age (NICHD ECCRN, 2003a, 2003b, 2003c). They found that the putative effect of long hours in any type of care was a function of time spent in the care of nonrelatives (i.e., nannies, babysitters, day-care

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homes, centers) and not time spent in care provided by relatives (i.e., fathers, grandparents), and that it was center-based care in particular that most strongly related to problem behavior. Therefore, in the present work, we include a series of secondary analyses to ascertain whether findings pertaining to amount of time in any kind of care vary as a function of whether care is provided by a relative or non- relative, as the primary analyses focus upon the distinction between center- and home-based care and on overall quantity of care, just as it has in prior reports by our research team (NICHD ECCRN, 2003a, 2003b, 2003c, 2005a, 2005b, 2006).

A second set of follow-up analyses explores a delimited set of interactions. In particular, we ask whether links between amount and type of care and externalizing problems are more pronounced for boys than for girls and whether the relations linking quality of care with academic achievement are more pronounced among children growing up in low-in- come households. Although the NICHD SECCYD has not found support for these moderated effects before (NICHD ECCRN, 2000, 2002, 2003a, 2003b), they merit consideration given enduring hypotheses about their importance (Crockenberg, 2003; Love et al., 2003; Maccoby & Lewis, 2003).

Method

Participants

Families were recruited through hospital visits to mothers shortly after the birth of a child in 1991 in 10 locations in the United States. During selected 24-hr intervals, all women giving birth (n 5 8,986) were screened for eligibility. From that group, 1,364 fam- ilies completed a home interview when the infant was 1-month-old and became the study participants. Details of the sampling plan can be found in NICHD ECCRN, 2005a). In terms of demographic charac- teristics, 26% of the mothers had no more than a high school education at the time of enrollment; 21% had incomes no greater than 200% of the poverty level at sixth grade; and 22% were minority (i.e., not non- Hispanic European American).

As with any longitudinal study, not all families participated in every wave of data collection. Rela- tively few families formally withdrew (N 5 291 through sixth grade), but almost all children had at least some missing data. Indeed, only 293 children had complete data on all predictors and outcomes included in any analysis. Children were least likely to be missing direct assessments and most likely to be missing teacher ratings. Children with complete

data tended to be from families with more income, to have parents who provided more responsive and stimulating care, to experience more center care and spend more time in child care, and to show higher academic achievement scores over time than did children with missing data. Children with and without missing data did not differ reliably on child- care quality or teacher ratings.

Measures

Measurements are described in terms of their roles in the analyses to be reported. Measures re- flecting the child’s experiences in child care before school entry are described first. The variables used to control for family factors (i.e., family covariates) are described next. Then measures used to control for school and after-school experiences are described. Finally, we describe child social and cognitive out- come measures. Information about this public data set can be found at http://secc.rti.org/.

Child-Care Characteristics

Nonmaternal child care was defined, as already noted, as regular care by anyone other than the motherFincluding fathers, relatives, and nannies (whether in home or out of home), family day-care providers, and centers. Three aspects of child care were measured from birth through 54 months: the quantity of care, the quality of care, and the type of care.

Child-care quantity. Parents reported children’s hours of routine nonmaternal care during phone and personal interviews conducted at 3-month intervals through 36 months and at 4-month intervals there- after, as well as the type(s) of child care being used. The hours spent in all settings were summed for each of the 17 intervals or ‘‘epochs’’ and parameterized on an hours-per-week basis. Individual measures of lev- el and rate of change in quantity of care were computed as the individual intercepts and slopes from an unconditional hierarchical linear modeling (HLM) analysis of these 17 repeated measures. Age was centered at the measurement midpoint, 27 months; hence, the estimated intercept reflected that child’s hours per week at 27 months of age. In order to carry out the secondary analyses distinguishing effects attributable to relative and nonrelative care, the hours per week children spent in care proved by fathers, romantic partner of mother, or grandparents (labeled relative care), and/or by other people be- sides the mother (labeled nonrelative) was also computed. The hours per week in relative care and

684 Belsky et al.

separately in nonrelative care were tallied for each time point, and then the mean across time was computed.

Child-care type. For each epoch, each of the child’s care arrangements was classified as center, child-care home (any home-based care outside the child’s own home except care by grandparents), in-home care (any caregiver in the child’s own home except father or grandparent), grandparent care, or father care. The proportion of epochs in which the child received care in a center for at least 10 hr/week and the pro- portion of epochs in a child-care home for at least 10 hr/week were determined and were used as variables to represent type of care.

Child-care quality. Observational assessments were conducted in the primary child-care arrangement at ages 6, 15, 24, 36, and 54 months. Quality was as- sessed during two half-day visits scheduled within a 2-week interval at 6 – 36 months and one half-day visit at 54 months. Observers completed four 44-min cycles of the Observational Record of the Caregiving Environment (ORCE) per child age through 36 months and two 44-min ORCE cycles at 54 months. Detailed descriptions of the ORCE assessments can be found in NICHD ECCRN (2002), including coding definitions, training procedures, and interobserver agreement. Reliability exceeded .90 at 6 months, .86 at 15 months, .81 at 24 months, .80 at 36 months, and .90 at 54 months. As with quantity, individual measures of level and change in quality were esti- mated with an unconditional HLM analysis. Many children were not in child care for at least three time points, and therefore their slopes could not be com- puted and preliminary analyses based on imputed data did not suggest that the quality slope contrib- uted to analysis models. Therefore, only the quality intercept was included in the reported analyses. The quality of relative and nonrelative care was also computed for the purposes of carrying out the sec- ondary analyses. A mean quality score was com- puted for each setting.

Maternal, Child, and Family Controls

Early childhood covariates. Measures of maternal, child, and family characteristics during infancy and early childhood were collected and used as controls for possible selection bias: maternal education (in years); the study child’s race and ethnicity; the pro- portion of (five measurement) epochs through 54 months in which the mother reported a husband/ partner was present; family income through 54 months calculated as the mean income-to-needs ratio; and the intercept and slope of maternal depressive

symptoms assessed by the Center for Epidemiological Studies Depression (CESD) Scales reported by the mother at 6, 15, 24, 36, and 54 months, determined by HLM analyses. Composite parenting quality scores were created by first averaging standardized ratings of observed maternal sensitivity and of observed home environmental quality at 6, 15, 24, 36, and 54 months and then estimating their intercept and slope in HLM analyses. These control variables are described in detail in NICHD ECCRN (2002). Subsequent maternal CESD and income/needs ra- tios were included in the analyses as time-varying covariates.

Primary-grades’ family covariate. Measures of fam- ily demographic and psychological characteristics also were obtained when children were in kinder- garten and in first, third, and fifth grades. These were included as time-varying covariates in the HLM analyses of child outcomes. These factors were presence of a husband/partner in the household, income- to-needs ratio, maternal depressive symptoms, and par- enting quality.

Measures of parenting quality were collected every 2 years using videotaped mother – child interactions involving 15-min semistructured tasks (NICHD ECCRN, 2003a). At 54 months, the task included completing a maze using an Etch-A-Sketch, building a series of identical towers from blocks of varying shapes and sizes, and playing together with six hand puppets. During the first-grade assessment, the interaction tasks included working together to draw a picture of a house and a tree using an Etch- A-Sketch (with the mother controlling one knob and the child the other), a patterned block activity using colored blocks of different parquet shapes to fill in geometric frames, and a card game. These activities provided a context for observing the mother ’s support for the child in activities that could be frustrating but also an opportunity for fun together. Two activities were used to assess maternal sensi- tivity in third and fifth grades. The first activity at both measurement occasions was a discussion of topics that were sources of disagreement between the mother and child and chosen by them for con- sideration from a list provided. The second activity was a planning task. In third grade, the dyad was given the challenge of planning the route on a spe- cially prepared map for completing 11 errands while doing as little back-tracking as possible; in fifth grade, the task was to create a bungee jump for an egg, using a platform and a pair of nylon stockings (as the bungee cord) that would allow the egg to fall within 2 in. of a table top and not break.

Early Child Care 685

As was the case for earlier observational assess- ments, videotapes from all data collection sites were shipped to the same central location for coding. Teams of three or four coders scored the mother – child interaction videotapes from each time period, with one or two members of a coding team carrying over from one time period to the next. Coders were blind as to other information about the families. Coders received intensive training and supervision and typically met weekly or biweekly to recode tapes together as a group throughout the period of formal scoring. Complete operational and coding manuals can be found at http://secc.rti.org/. Maternal sen- sitivity scores at each assessment age were the sum of the 7-point ratings of supportive presence, respect for autonomy, and hostility (reversed). Cronbach as for the sensitivity composite scores ranged from .80 to .85 and interrater reliabilities determined from intraclass correlations (Winer, 1971) based on a sec- ond coding of 19.5% (196/1,004) to 27% (271/987) of the videotapes at the different ages ranged from .84 to .91.

The Home Observation for Measurement of the Envi- ronment (HOME; Caldwell & Bradley, 1984) was ad- ministered during home visits at 54 months and in third and fifth grades. The focus is on the child as a recipient of inputs from objects, events, and trans- actions occurring in connection with the family sur- roundings. Information is obtained during the course of a home visit by means of observation and semistructured interview. A centrally located system of training was used for data collectors at each age. Every 4 months, observers coded videotaped visits and the coding was compared with gold standard codes. All observers were required to maintain a criterion of agreement with the master coder on 90% of the items. Cronbach as for the total score at each age exceeded .82.

The HOME and maternal sensitivity ratings were standardized and averaged at each age to create a composite score, using an average of the 54-months and third-grade HOME to impute the missing first- grade HOME scores. Together, these combined scores reflect parenting in two contexts: in the home and during semistructured play. We have found this composite parenting rating to be a strong and con- sistent predictor of children’s cognitive and social competencies at earlier ages (ECCRN, 2002, 2003a, 2005c). Two indexes of parenting quality (the inter- cept and slope) were created from the mean of the standardized scores at each age using HLM. The composite parenting scores from 54 months through fifth grade were entered as time-varying concurrent controls in the second set of analyses.

Classroom Quality in the Primary Grades

Children’s classroom experiences were measured using the Classroom Observation System for First Grade (NICHD ECCRN, 2004a), the Classroom Ob- servation System for Third Grade (NICHD ECCRN, 2005c), and the Classroom Observation System for Fifth Grade (NICHD ECCRN, 2004c). These obser- vations focused on the classroom as well as the specific study child and his or her classroom expe- riences. In first grade, two 44-min observations were conducted during the morning. In third and fifth grades, classrooms were observed for eight 44-min cycles distributed across the school day. Three 7- point global ratings of the classroom environment were made at the end of each observation cycle: overcontrol by teacher, and teacher ’s emotional de- tachment, teacher ’s sensitivity to student needs.

Observers from all 10 sites first trained on practice videotapes using a standardized detailed manual and attended a centralized training workshop. All observers passed a videotaped reliability test in- volving six cases. The average reliability for the teacher and classroom global ratings on the video- taped test was estimated at .60 using a correlation method and .69 using intraclass correlations (Winer, 1971). For more details on the derivation of these composites and the individual scales of which they are composed, see NICHD ECCRN (2004a, 2005c).

After-School Experience

Mothers were interviewed by telephone in the fall and spring of kindergarten and first, third, and fifth grades about the study children’s out-of-school care. They were asked a series of questions about a number of possible out-of-school care arrangements. In the present study analyses, hours of nonparental out-of-school care arrangements (here named after- school hours) were obtained for each school year from the average across the spring and fall reports of the total hours mothers reported across all nonparental out-of-school care arrangements.

Child Outcomes

Cognitive and social outcomes were assessed re- peatedly over time. Standardized cognitive-aca- demic achievement tests were administered at 54 months and at the end of first, third, and fifth grades. Caregiver/teacher reports of children’s behavior problems were collected at 54 months, kindergarten, and annually in first, second, third, fourth, fifth, and sixth grades; social skills from K through sixth grade;

686 Belsky et al.

and emotional functioning and academic work hab- its annually in first though sixth grade.

Academic achievement. With respect to cognitive- academic achievement, children were administered four subtests from the Woodcock – Johnson Psycho- Educational Battery – Revised: Letter – Word Identifi- cation (54 months and first grade), which assesses prereading skills in identifying isolated letters, and words and Broad Reading (third and fifth grades), which adds assessment of passage comprehension to the assessment of identification of words; Applied Problems, which measures skill in analyzing and solving practical problems in mathematics; and Pic- ture Vocabulary, which measures children’s ability to name objects depicted in a series of pictures. Items are presented in order of increasing difficulty and are scored 0 5 incorrect or no response, or 1 5 correct re- sponse, with basal and ceiling levels established. Typically, raw scores are converted to standard scores with a mean of 100 and a standard deviation of 15, but for this study we relied upon W ability scores so that change over time could be more easily documented. The W ability scores are transform- ations of the Rasch raw ability scores designed to eliminate the need for decimal fractions and negative values. The overall Woodcock – Johnson – Revised battery of tests has been standardized on a nationally representative sample from 24 months to 95 years of age. Internal-consistency reliability for the full bat- tery of subscales ranged from .94 to .98, with test – retest reliability ranging from .80 to .87. Moreover, the subtests used here correlated substantially with other cognitive assessments (McGrew, Werder, & Woodcock, 1991) and have been found in previous work with the current sample to relate strongly to aspects of experience presumed to influence aca- demic achievement, most notably quality of parent- ing, (NICHD ECCRN, 2005b).

Social skills. The Social Skills Questionnaire from the Social Skills Rating System (SSRS; Gresham & Elliott, 1990) was used to assess social competence and social skills. This instrument is composed of 38 items describing child behavior, each rated on a 3- point scale reflecting how often the child exhibited each behavior. Items are grouped into four areas: cooperation (e.g., ‘‘keeps room neat and clean with- out being reminded’’), assertion (e.g., ‘‘makes friends easily’’), responsibility (e.g., ‘‘asks permission before using someone else’s property’’), and self-control (e.g., ‘‘controls temper when arguing with other children’’). The total score used in this report repre- sents the sum of all 38 items, with higher scores re- flecting higher levels of perceived social skills (as range from .86 to .94).

Behavior problems. The Child Behavior Checklist Teacher Report Form (TRF; Achenbach, 1991) was used to evaluate problem behavior. The TRF lists 100 problem behaviors that generate two subscales: in- ternalizing problems (e.g., ‘‘too fearful and anxious’’) and externalizing problems (e.g., ‘‘hits others,’’ ‘‘disobedient at school,’’ ‘‘argues a lot’’). Achenbach reports a test – retest reliability of .89, an interparent agreement of .70, and a stability of .71 over 2 years. Raw scores were converted into standard T scores, based on normative data for children of the same age.

Conflict with teacher. The Student – Teacher Rela- tionship Scale (STRS; Pianta, 2001) was completed by caregivers/teachers. The STRS is a widely used in- dicator of a teacher ’s perceptions of the quality of his or her relationship with a specific child. In the cur- rent report, we focused on teacher – child conflict (e.g., ‘‘dealing with this child drains my energy’’), which was assessed by 7 items rated using 5-point Likert scales. Coefficient as for the conflict subscale ranged from .88 to .91 across grades.

Work habits. Teachers completed a 19-item mock report card. This questionnaire includes 6 items ad- dressing the child’s work habits. The items, each rated on a 5-point scale (1 5 very poor to 5 5 very good), were taken from Madison (Wisconsin) Metropolitan School District report cards. The 6 items include ‘‘follows classroom procedures,’’ ‘‘works well inde- pendently,’’ ‘‘works neatly and carefully,’’ ‘‘uses time wisely,’’ ‘‘completes work promptly,’’ and ‘‘keeps material organized.’’ Scores were based on the mean of the items at each age. Coefficient as were high, ranging from .94 to .95.

Socioemotional functioning. Teacher-reported so- cial – emotional functioning was obtained from the mock report cards. The 7 items included that ad- dressed social – emotional functioning came from the Teacher Checklist of Peer Relations (Coie & Dodge, 1988) and rated on a 5-point scale (1 5 very poor to 5 5 very good). Items addressed the children’s social skillfulness with peers, such as ‘‘generates good quality solutions to interpersonal problems’’ and ‘‘is aware of the effects of his/her behavior on others.’’ Cronbach as ranged from .94 to .95.

Data Analysis Plan

Data analysis focused on testing the long-term associations between child-care experiences during the first 4 1

2 years and children’s academic and social

development from that age through the spring of sixth grade. HLM (Bryk & Raudenbush, 2002; Singer & Willett, 2003) were fitted to estimate individual and group linear and quadratic growth curves. The

Early Child Care 687

models included both preschool and concurrent family and child-care/school experiences. Individu- al intercepts and linear slopes with respect to age were estimated as correlated random effects for each child for each outcome. These individual-level pa- rameters were related to predictors of interest and covariates. The predictors of primary interest were the five indexes of child-care experiences (across the period 3 – 54 months): proportion of 3 – 4 month ep- ochs in center-based child care for at least 10 hr/ week, proportion of 3 – 4 month epochs in a child- care home for at least 10 hr/week, the hours per week intercept (estimated from HLM analyses in which the intercept was set at 27 months, reflecting the midpoint between 3 and 54 months), the hours per week slope (estimated linear change over time in hours per week), and the quality intercept (estimated quality of care at 27 months). The preschool time- invariant covariates included site, child ethnicity, child gender, maternal education, mean income-to- needs ratio between 6 and 54 months, parenting intercept, and slope from 6 to 54 months, maternal depressive symptoms intercept and slope from 6 to 54 months. The concurrent time-varying covariates from 54 months through sixth grade included in- come-to-needs ratio, parenting, maternal depression, observed school classroom quality, and hours per week of after-school care (set to 0 for 54 months).

Several modeling decisions were made. All child- care predictor variables and covariates were centered at the sample mean to enhance interpretation of main effects. Age was centered at the mean age for spring of the final assessment periodFfifth grade for academic achievement and sixth grade for teacher ratings. Thus, the main effect coefficient for each child-care predictor indicates the extent to which that variable was related to the outcome in the spring of either fifth or sixth grade, that is, the most recent time of measurement for that outcome. When the child-care predictors showed interactions with age, we estimated coefficients for that child-care variable at each of the ages at which the outcome was measured (Aiken & West, 1991). This approach al- lows for a representation of interactions between age and continuous variables in a way that illus- trates findings from the analysis that produced those interactions.

Missing data occurred in this longitudinal project due to attrition and failure to complete all assess- ments. Missing data were imputed using multiple imputation (Rubin, 1987; Schafer, 1997; Schafer & Graham, 2002) under the assumption that missing data were ignorably missing. That is, given our many longitudinal measures on demographic, child,

family, and child-care measures, there was sufficient information in our data to estimate missing data accurately (rather than rely on simple mean substi- tution). Schafer ’s (1997; Schafer & Graham, 2002) recommended procedure, an iterative E-M algo- rithm, was used. Missing values for each variable are estimated iteratively using a logistic or multiple re- gression from all the other variables using the data for all individuals with observed values on that variable, and random variability is added as the missing data are predicted. The process is repeated for each variable until the differences in predicted values across iterations are miniscule. Five data sets were created in which all observed data are repre- sented and missing data are estimated. Conse- quently, analyses were conducted five times, using each of the five imputation data sets. The results of these analyses were combined using the recom- mended procedures of Schafer (1997) to ensure that variability in imputed values across the data sets as well as variability in the variables within the data set were considered. The test statistics and regression coefficients were averaged across the five analyses, and the standard errors for the coefficients were combined by combining within- and between-model variability.

Effect sizes were computed when child-care variables showed a significant association with child outcome trajectories. Effect sizes were computed to show the anticipated difference in standard devi- ation units of the outcome measure between children who had child-care experiences that differed by one standard deviation (for details, see NICHD ECCRN & Duncan, 2003). The effect sizes were computed as the product of the estimated child-care coefficient and the standard deviation for the child-care index divided by the standard deviation for the outcome measure, and can be interpreted somewhat like a correlation. For example, the standard deviation for our child-care quality measure was .23; therefore, the effect size compared predicted outcome scores for children whose child care differed in quality by .23 points on the ORCE measure of child-care quality.

Results

Descriptive Analyses

The descriptive statistics for all child-care and family measures from the early childhood period are shown in Table 1 and for the academic and social outcomes and concurrent school and family charac- teristics are shown in Table 2. Correlations among the child-care variables, the family, and school

688 Belsky et al.

covariates, and the child outcomes that are shown in Table 3 indicate that most of the child-care variables were modestly correlated. Stronger correlations ap- peared between the amount and type of child care, indicating that children who spent more hours per week in care (hours intercept) were more likely to have spent more months in either a center or a child- care home. The correlations between quantity and quality of care in relative and nonrelative care were modestly correlated. As children spent more time in nonrelative care, the quantity and quality of care in nonrelative care were somewhat more strongly cor- related with overall measures of quantity and quality than were quantity and quality in nonrelative care. As shown in Table 4, the three academic measures and the five teacher ratings were strongly correlated. Finally, Table 5 shows the correlations between the child-care variables and child outcomes at the final age at which all outcomes were collected. Most of these correlations were modest in magnitude. It ap- peared that quality of relative care was a somewhat stronger positive correlate of academic outcomes than quality of nonrelative care, but that quantity of nonrelative care was a somewhat stronger negative correlate of teacher rating of behavior between 54 months and in first grade than at subsequent ages.

Primary Longitudinal Prediction Analyses

Two sets of hierarchical linear model analyses of the child outcomes from 54 months through sixth grade were conducted. The first primary set of analyses included the five child-care measures that reflected the type, quantity, and quality of care dur- ing early childhood. In addition, all analyses in- cluded site and selected child and family measures from early childhood as covariates to control for possible selection factors. The second set of analyses examined the extent to which care by relative and nonrelatives predicted trajectories, controlling for the same covariates; the results of these analyses are described in the secondary analysis subsection.

Table 6 presents the primary results from first set of HLM analyses after aggregating the results across the analyses of the five imputation data sets. Owing to the primary focus of this report on effects of child care and in the interests of space, Table 6 presents the coefficients for the main effect and interaction with age for each of the five selected child-care indexes. In the bottom subsection of the table, coefficients per- taining to parenting are presented to provide a comparison for the coefficients for the child-care variables because it is widely accepted that parenting

Table 1

Descriptive Statistics: Early Childhood Child Care and Family Measures

Child-Care Variables N Mean SD Minimum Maximum

Overall

Proportion of timeaFcenter care: 1 – 54 months 1,214 0.21 0.26 0 0.94

Proportion of timeaFchild care home: 1 – 54 months 1,214 0.19 0.28 0 1.00

Hours per week 1 – 54 months: intercept 1,268 24.90 16.00 �0.77 61.33 Hours per week 1 – 54 months: linear change 1,268 0.23 0.31 �1.05 1.24 ORCE quality total 6 – 54 months: intercept 1,134 2.81 .23 2.07 3.44

In care by relatives

Hours per week: 1 – 54 months 1,214 7.37 9.83 0 53.71

Mean ORCE quality total: 6 – 54 months 426 2.99 0.50 1.55 3.95

In care by nonrelatives

Hours per week of care: 1 – 54 months 1,214 16.48 14.16 0 52.76

Mean ORCE quality total: 6 – 54 months 1,005 2.90 0.45 1.35 4.00

Family variables

Mother’s education 1,363 14.23 2.51 7 21

Proportion of timeb Partner in HH: 1 – 54 months 1,305 0.84 0.32 0 1

Income/poverty threshold: mean 6 – 54 months 1,302 3.60 2.85 0.15 27.36

Maternal depression (CESD) 6 – 54 months: intercept 1,304 9.35 5.49 1.39 33.57

Maternal depression (CESD) 6 – 54 months: linear change 1,260 0.19 0.64 �3.10 4.05 Parenting 6 – 54 months: intercept 1,306 �0.03 0.67 �3.19 1.27 Parenting 6 – 54 months: linear change 1,261 �0.01 0.07 �0.32 0.20

Note. CESD 5 Center for Epidemiological Studies Depression; ORCE 5 Observational Record of the Caregiving Environment. aProportion of 17 measurement epochs. bProportion of 5 measurement epochs.

Early Child Care 689

Table 2

Descriptive Statistics: Longitudinal Child Outcomes and Family Measures from 54 months to Grade 6

Age at Assessment

54 K G1 G2 G3 G4 G5 G6

Child Outcomes

WJ Letter Word/Broad Reading W score

N 1,056 1,025 1,011 993

Mean 369.4 452.6 494.6 507.6

SD 21.41 23.99 15.75 14.12

WJ Applied Problems/Broad Math W score

N 1,053 1,023 1,012 993

Mean 424.7 470.0 493.5 510.5

SD 19.27 15.54 12.76 13.04

WJ Picture Vocabulary W score

N 1,060 1,020 1,014 992

Mean 459.5 483.9 496.9 505.8

SD 14.09 12.27 11.51 12.08

Teacher report CBCL externalizing

N 714 1,004 1,007 921 982 914 927 855

Mean 50.09 49.72 50.68 50.51 51.51 50.46 50.96 50.16

SD 9.61 8.86 8.72 8.91 9.36 9.09 9.15 9.12

Teacher report SSRS total

N 993 1,000 913 975 906 921 842

Mean 103.5 103.2 105.1 102.2 102.4 102.8 102.9

SD 14.05 13.64 14.52 14.48 13.94 14.44 14.26

Teacher report STRS Conflict

N 716 1,006 1,006 935 978 915 930 857

Mean 18.88 10.60 10.92 10.94 11.62 11.14 11.44 11.07

SD 6.66 5.36 5.17 5.41 6.03 5.73 5.74 5.64

Teacher report ECLS Social – emotional evaluation

N 1,005 918 993 932 940 866

Mean 3.52 3.62 3.55 3.59 3.66 3.65

SD 0.87 0.96 0.90 0.90 0.89 0.88

Teacher report work habits evaluation

N 1,006 920 992 930 941 871

Mean 3.55 3.63 3.58 3.64 3.70 3.69

SD 1.05 1.11 1.08 1.07 1.04 1.12

Family and School Covariates

Income/poverty threshold

N 1,073 1,027 982 982 985 996 979

Mean 3.59 3.49 3.95 4.39 4.50 4.53 4.54

SD 3.17 2.69 3.03 3.77 3.88 4.06 4.15

Maternal depression: CESD score

N 1,077 1,099 1,009 1,103 1,026 1,077 1,019 1,023

Mean 9.83 9.30 8.39 8.78 9.08 8.91 8.73 8.96

SD 8.70 7.72 8.47 7.84 8.85 7.78 8.62 8.82

Parenting

N 1,069 1,142 1,139 1,139 1,032 1,078 1,038 1,038

Mean �0.00 �0.02 �0.03 �0.02 �0.01 �0.02 �0.01 �0.01 SD 0.85 0.81 0.86 0.82 0.86 0.79 0.86 0.86

Partner in home

N 1,084 1,059 1,034 1,123 1,076 1,059 1,030 1,025

Proportion 0.83 0.83 0.82 0.81 0.81 0.80 0.81 0.81

690 Belsky et al.

is strongly linked to children’s development (NI- CHD ECCRN, 2004a, 2004b, 2004c). The main effect coefficients represent the estimated associations be- tween child care and child outcomes at the final as- sessment (fifth grade for the academic outcomes, sixth grade for teacher questionnaires). The age interaction coefficients indicate the extent to which the associations between child care and child out- comes change over time. Coefficients that were deemed significant (po.05) are given in bold. In addition, effect sizes were estimated to describe the association between each select child-care index and that child outcome at most assessment ages. Coeffi- cients for covariates are not presented (except, for comparative purposes, in the case of parenting) to preserve space and because of the difficulty in in- terpreting them due to the high correlations between

the measures collected during early childhood and concurrently.

Child-Care Quality

The first rows in Table 6 present the results re- garding child-care quality. The quality intercept (es- timated quality at 27 months) was significantly and positively related to one outcome, vocabulary (pic- ture vocabulary): Children who had experienced higher quality care had higher vocabulary scores in fifth grade (B 5 3.15, po.05; d 5 .06). This association did not change reliably over time; that is, the Age � Child-Care Quality interaction was statistically non- significant. Child-care quality became a significantly weaker predictor of reading skills over time (B 5 �1.08, po.05). Children who experienced higher

Table 2. (Contd)

Age at Assessment

54 K G1 G2 G3 G4 G5 G6

Classroom quality

N 854 966 971 955

Mean 2.98 3.43 3.17 3.21

SD 0.56 0.47 0.48 0.36

Hours in after-school care

N 1,071 1,040 1,014 1,054 1,046 1,047 1,047

Mean 9.28 6.54 6.35 5.65 5.81 6.08 6.08

SD 9.47 5.98 5.78 5.33 5.42 5.26 5.26

Note. CESD 5 Center for Epidemiological Studies Depression; SSRS 5 Social Skills Questionnaire from the Social Skills Rating System; STRS 5 Student – Teacher Relationship Scale.

Table 3

Correlations Among Child Care Variables

% CC

home

Hours per

week intercept

Hours per

week slope

CC quality

intercept

Relative

hours Quality

Nonrelative

hours Quality

Overall

% Centera � .17�� .40�� .11�� .21�� .12�� .05 .45�� .16��

% CC homea .45�� .08�� .05 � .12�� .01 .51�� .10��

Hours intercept .01 � .10�� .31�� .02 .71�� .21��

Hours slope � .07� � .07�� .07� � .07�� .05 Quality intercept .09�� .53�� .15�� .55��

Relative care

Hours mean .11�� .26�� .07 Quality mean � .08 .10��

Nonrelative care

Hours mean � .17��

Note. aProportion of 17 measurement epochs. �po.05, ��po.01, ��po.005.

Early Child Care 691

quality care had significantly higher reading scores at 54 months (B 5 6.47, po.05; d 5 .06), but this as- sociation was no longer significant by first grade or thereafter, becoming quite small by fifth grade (B 5 0.01, p4.05; d 5 .001).

Quantity of Child Care

The next set of rows display the coefficients and effect sizes associated with the intercept and slope from the unconditional HLM analysis of hours of child care (i.e., the expected hours of care at 27 months and linear change in hours from 1 to 54 months, respectively). The hours intercept became a statistically significant weaker predictor of teach- er ratings of externalizing problems (B 5 � .012, po.001) and teacher – child conflict (B 5 � .009, po.001) over time, eventually turning nonsignificant. The association between the hours per week of care in early childhood and teacher ratings of externalizing problems ranged from a significant B 5 .065 (po.001; d 5 .11,) at 54 months to a nonsignificant B 5 � .018 (p4.05; d 5 � .03) at sixth grade. Similarly, the asso- ciation between hours per week of care and teacher ratings of conflict ranged from a significant B 5 .052 (po.001; d 5 .12) at 54 months to a nonsignificant B 5 � .008 (p4.05; d 5 � .02) at sixth grade.‘

The hours’ slope emerged as a significant pre- dictor of one outcome. This previously undetected association indicated that children whose hours of child care increased more over time (i.e., from 3 to 54 months) had significantly lower vocabulary scores in fifth grade (B 5 �2.67, po.05; d 5 � .07). This ‘‘sleeper effect’’ result was explored in subsequent analyses to determine whether it might be an artifact of other factors/processes because no link between quantity of child care and cognitive – language de- velopment had heretofore been detected in child-

care analyses carried out at earlier ages (NICHD Early Child Care Research Network, 2005a, 2005b, 2006). These follow-up analyses focused on family and school characteristics and involved two steps: first identifying which such variables were correlat- ed with change in quantity of child care and then testing whether these identified variables accounted for the association between change in quantity of child care and vocabulary development. Whereas school characteristics proved to be unrelated to change in child care quantity during early child- hood, both the age of entry into child care, w2(8, n 5 1,364) 5 296, po.001, and whether the family was poor during early childhood (indicated by mean of 6 – 54 months income/needso2.0) w2(2, n 5 1,364) 5 39, po.001, were significantly related. When these two variables were included in the prediction model (as main effects and an inter- action), linear change in hours no longer significantly related to vocabulary scores. Instead, the interaction between age at entry to child care and whether the family was poor (median income/needso2) indi- cated that whereas there was no significant associa- tion between entry age and vocabulary among children whose families were not poor, among low- income children vocabulary scores varied as a function of age of entry to care: Scores were higher if (poor) children entered child care before 3 months of age or after 9 months of age and lower if they entered between 3 and 9 months.

Type of Child Care

The next set of rows presents the coefficients asso- ciated with the proportion of epochs in which the mother reported that the child attended a center or was in a child-care home. Only one association was statis- tically significant: Teachers reported more problem

Table 4

Correlations Among Outcome Measures in Fifth Grade

WJ-R reading

WJ-R

math

WJ-R

vocabulary

TRF

external

CTRS

conflict

SSRS social

kkills

ECLS social/

emotionl

Work

habits

Reading .68�� .67�� .20�� .19�� .29�� .35�� .36��

Math .56�� .22�� .21�� .34�� .37�� .40��

Vocabulary � .19�� .18�� .24�� .28�� .25��

Externalizing .76�� .60�� .65�� .55��

Conflict � .62�� .65�� .56��

Social skills .70�� .68��

Social – emotional Work habits .70��

Note. SSRS 5 Social Skills Rating System; TRF 5 Child Behavior Checklist Teacher Report Form. �po.05, ��po.01, ��po.005.

692 Belsky et al.

behaviors for children who spent more time in centers (B 5 2.85; po.01; effect size d 5 .08). This association did not change reliably over time; the Age � Center care interaction was not statistically significant.

Parenting Quality

In marked contrast to the child-care effects just described, parenting quality significantly predicted

all the developmental outcomes and much more strongly than did any of the child-care predictors. Higher levels of parenting quality (i.e., intercept) predicted greater tested reading, math, and vocabu- lary achievement in fifth grade and lower levels of teacher-rated externalizing problems and conflict and higher levels of social skills, social – emotional functioning, and work habits in sixth grade. The magnitude of parenting effects on math and

Table 5

Correlations Between Child Care Variables and Longitudinal Child Outcomes

Nonmaternal care Relative care Nonrelative care Parents

Centera

% Child

care

homea

Hours

per week

intercept

Hours

per week

slope

Quality

intercpt

Hours

per

week Quality

Hours

per

week Quality

Parenting

intercpt

WJ-R reading 54 months .09�� .01 .08� � .05 .23�� .01 .30�� .07� .14�� .44��

G1 .08� .00 .06 � .09�� .16�� .02 .20�� .08�� .11�� .34��

G3 .06 .02 .07� � .09�� .19�� .01 .25�� .06 .11�� .45��

G5 .03 .02 .05 � .10�� .19�� .02 .23�� .05 .13�� .48��

WJ-R math 54 months .07� .05 .07� � .06� .21�� .09�� .21�� .09�� .20�� .52��

G1 .10�� .01 .08� � .06� .19�� .08�� .26�� .13�� .13�� .43��

G3 .07� .02 .09�� .06� .18�� .04 .24�� .10�� .14�� .40��

G5 .04 .00 .07� � .09�� .18�� .05 .24�� .08� .16�� .45��

WJ vocabulary 54 months .06 .02 .06 � .11�� .24�� .06 .30�� .07� .20�� .51��

G1 .05 .01 .04 � .09�� .22�� .01 .29�� .04 .15�� .50��

G3 .06� .07� .09�� .11�� .23�� .00 .29�� .08� .14�� .48��

G5 .04 .06 .06 � .16�� .22�� .03 .26�� .07� .15�� .48��

T externalizing 54 months .16�� .04 .22�� .07 � .14�� .03 � .15� .21�� .16�� .26��

G1 .11�� .08� .14�� .05 � .09�� .01 � .06 .17�� .11�� .30��

G3 .10�� .00 .10�� .11�� .17�� .01 � .20�� .10�� .15�� .37��

G5 .04 .02 .03 .05 � .15�� .00 � .21�� .05 � .11�� .34��

G6 .04 .03 .07 .06 � .10�� .00 � .21�� .05 � .11�� .34��

STRS conflict 54 months .15�� .02 .18�� .05 � .14�� .01 � .12 .19�� .16�� .16��

G1 .09�� .11�� .15�� .03 � .12�� .02 � .09 .18�� .11�� .22��

G3 .04 � .00 .04 .10�� .15�� .01 � .19�� .06 � .14�� .32��

G5 .03 � .01 .02 .07� � .10�� .03 � .16�� .02 � .09� � .35��

G6 .00 .02 .03 � .00 � .09�� .02 � .15�� .05 � .07 � .29��

SSRS social skills 54 months � .04 .03 � .07 � .11�� .13�� .04 .14� � .03 .18�� .27��

G1 � .07� � .02 � .07� � .07� .13�� .04 .22�� .06 .12�� .33��

G3 � .01 .03 .00 � .08� .15�� .03 .19�� .01 .12�� .32��

G5 .00 .05 .03 � .08� .15�� .06 .23�� .06 .10�� .36��

G6 .05 .04 .01 � .09� .11�� .05 .22�� .04 .07 .35��

ECLS Social – emotional

G1 � .06 � .05 � .08� � .07� .15�� .02 .12� � .09�� .11�� .36��

G3 � .03 .02 � .02 � .12�� .17�� .03 .22�� .00 .13�� .40��

G5 .02 .02 � .01 � .08� .17�� .04 .22�� .02 .11�� .40��

G6 .05 .00 .00 � .07� .13�� .03 .23�� .02 .11�� .40��

Work habits G1 � .05 .00 � .04 � .08� .13�� .06 .14�� .03 .11�� .37��

G3 � .00 .02 � .01 � .06 .17�� .08�� .16�� .01 .13�� .40��

G5 .03 .04 .05 � .07� .14�� .04 .18�� .06 .10�� .42��

G6 .05 .04 .03 � .05 .17�� .04 .23�� .04 .14�� .41��

Note. SSRS 5 Social Skills Questionnaire from the Social Skills Rating System; STRS 5 Student – Teacher Relationship Scale. aProportion of 17 measurement epochs. �po.05, ��po.01, ��po.001.

Early Child Care 693

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694 Belsky et al.

vocabulary achievement weakened over time, as re- vealed by a significant interaction with age, but nevertheless remained significant even at the final time of measurement.

Secondary Analyses

Two sets of secondary analyses were conducted. The first was based on the possibilities (a) that pre- viously detected effects of center-based child care and hours in any child care on externalizing prob- lems might be most likely to emerge for boys and (b) that previously detected effects of child-care quality on cognitive – academic achievement might be most likely to emerge for children from the most eco- nomically disadvantaged families (i.e., income-to- needs ratioo2.0). Models predicting externalizing problems and academic achievement were revised to include relevant interaction terms. As in previous analyses on children at younger ages (NICHD ECCRN, 2003a, 2005a, 2005b), no evidence emerged to indicate that that gender or income moderated the reported results.

A final set of secondary analyses focused on whether care was provided by close relatives or not, based on the results of a re-analysis of the 54-month NICHD SECC data carried out by van IJzendoorn et al. (2004) showing that the effect of time spent in any kind of child care on externalizing problems report- ed by the NICHD Early Child Care Research Net- work (2003a, 2003b, 2003c) was principally a function of time spent in nonrelative care. This led to the ex- pectation that distinguishing between nonmaternal care by relatives (i.e., fathers, grandparents) and by nonrelatives would reproduce already reported re- sults pertaining to social functioning, but principally in the case of care by nonrelatives rather than by relatives. To address this issue, the hours per week of care provided by a father or grandparent and the average quality of such care were distinguished from the amount and quality of care provided by anyone else and regression analyses were run predicting all the outcomes using measures of hours and quality of care separately for the two groups of care providers (i.e., relatives, nonrelatives).

The results displayed in Table 7 of effects attrib- utable to each kind of care (i.e., top: by relatives; bottom: by nonrelatives) reveal a pattern of findings similar to those that emerged in the primary analyses (see Table 6) and, in general, consistent with those reported by van IJzendorn et al. (2004), in that sig- nificant effects emerged principally, even if not ex- clusively, in the case of care by nonrelatives. More specifically, hours per week of nonrelative care in-P

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Early Child Care 695

teracted with time such that between 54 months and sixth grade the amount of nonrelative care became less predictive of teacher ratings of externalizing problems (B 5 � .017, SE 5 .005, po.001) and conflict (B 5 � .010, SE 5 .003, po.001), and more predictive of social – emotional adjustment (B 5 .0013, SE 5 .0006, po.05) and work habits (B 5 .0014, SE 5 .0005, po.01). Finally, hours of nonrelative care was a modest positive predictor of math skills (B 5 .07, SE 5 .03, po.05), whereas hours of relative care was a significantly weaker predictor of teacher ratings of externalizing problems over time (B 5 � .014, SE 5 .005, po.01). These results were viewed as buttress- ing the findings reported above because hours of care by both relatives and nonrelatives were related to ratings of problems by the child’s teachers and in all cases became nonsignificant by the time the child was in sixth grade.

Discussion

This paper represents the latest installment in the ongoing study of relations between experiences in child care in the first 54 months of life and child development using data gathered in the NICHD SECCYD. Four issues were addressed in this report: (1) whether associations linking child functioning with child-care quality, quantity, and type detected before school entry and in first through third grade continued to be evident in fifth and sixth grade; (2) whether associations between child-care experiences and child development dissipated over time; (3) whether new relations emerged between child care and child development (i.e., sleeper effects); and (4) how relations between child care and child devel- opment compared, strengthwise, with linkages be- tween parenting quality and child development. In this latest installment at the end of fifth grade (for cognitive and academic outcomes) and sixth grades (for social and behavioral outcomes), we found evi- dence of all three patterns of relations between child care and child development just mentioned, as well as evidence that parenting quality proved to be a far stronger and more consistent predictor of tested achievement and teacher-reported social functioning than was child-care experience.

Two predictive associations involving child care first detected before school entry that were main- tained through third grade remained statistically significant in fifth and sixth grade; each is discussed in turn. First, children who experienced higher quality early child care (of any kind) displayed somewhat better vocabulary scores in fifth grade than did children who experienced poorer quality care. This potentially en-Ta

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696 Belsky et al.

during ‘‘effect’’ of child-care quality on vocabulary is consistent with other evidence indicating that chil- dren’s early experience matters to their language development. Perhaps the best example comes from Hart and Risley’s (1995) work tracking 42 families for 9 years and showing that one of the strongest pre- dictors of children’s vocabulary was adult talk, in- cluding talk in child-care settings. In fact, Hart and Risley (1995) concluded that community child care can serve as an effective intervention for low-income children who often do not experience a rich verbal environment in the home. Because vocabulary is one of the best predictors of reading (National Reading Panel, 2000), the long-term relations that emerged in the current work between child-care quality and vocabularyFfor all children (i.e., not just low-in- come ones)Fmay have important implications for education policy.

The second enduring link between early child care and child development detected in this inquiry in- dicated that children with more experience in center settings continued to manifest somewhat more problem behaviors through sixth grade. The fact that this result was not moderated by age means that this seemingly adverse consequence of center-based care did not dissipate as did so many other effects of amount of child care on social functioning detected previously. Because it was level of reported problems as mea- sured on a continuous scale that was the outcome to be explained in this inquiry, not clinical levels of problem behavior, no claim can or should be made on the basis of this report that center-based child care contributes to or predicts psychopathology.

Although it is not entirely clear why the predictive power of center-care experience vis-à-vis problem behavior remains unchanged through sixth grade, the fact that it does is consistent with van IJzendoorn et al.’s (2004) secondary analysis of 54-months data from the NICHD SECCYD. Recall that these inves- tigators found that predictive links between overall time in any kind of care and problem behavior re- ported by the NICHD Early Child Care Research Network (2003a, 2003b, 2003c) were accounted for not just by time in nonrelative care in general, but time in center care in particular. The fact that the findings from the secondary analysis reported herein (Table 7) showed that effects of time spent in any kind of nonrelative care on teacher-reported exter- nalizing problems became insignificant by sixth grade, as did effects of nonrelative care on teacher – child conflict, social – emotional adjustment, and academic work habits further underscores the uniquely enduring effect of center-based care. In- deed, when considered in their entirety, the results of

the primary and secondary analyses suggest that not only does it matter whether care is provided by relatives or nonrelatives, but whether nonrelative care takes the specific form of center-based care. Consider first in this regard that the data presented in Table 7 indicate that previously reported findings linking time in any kind of care with teacher – child conflict, social – emotional competence, and aca- demic work habits (NICHD Early Child Care Re- search Network, 2005a, 2005b) were exclusively a function of time in nonrelative careFin that no main or age-moderated effect of hours of relative care proved significant for these outcomes, only age- moderated effects of nonrelative care (i.e., bottom of Table 7). The fact, however, that all the age-moder- ated effects of time in any kind of nonrelative care became insignificant by the time children were in sixth grade, whereas the effect of center care on ex- ternalizing problems remained significantFand did not dissipate in strengthFover time means that in the case of nonrelative care, it is center care that has unique a and enduring impact of a seemingly ad- verse kind.

One possible reason why relations between center care and problem behavior may remain is that pri- mary school teachers lack the training as well as the time to address behavior problems, given their pri- mary focus on academics (Rimm-Kaufman & Pianta, 2001). Ultimately, it will be important to identify the specific mechanisms that link center-care experience with problem behavior. Previous analyses show that even though time in nonmaternal care is related to somewhat less harmonious patterns of mother – child interaction in the first 3 years of life (NICHD Early Child Care Research Network, 1998) and to somewhat elevated rates of insecure infant – mother attachment when they coincide with low levels of maternal sensitivity (NICHD Early Child Care Re- search Network, 1997), it is not via attachment or parenting that time in child careFor in center care in particularFseems to operate when it comes to predicting problem behavior. As we noted in an earlier report, the actual mechanism of influence by which quantity of careFor in the current report, experience in center careFexerts the detected ‘‘effect’’ remains somewhat of a mystery (NICHD Early Child Care Research Network, 2003b), al- though some subsequent work by the NICHD Early Child Care Research Network (2007) highlights the potential role played by agemates and, thus, by peer processes.

Whatever the reasons that quality and type of care remained associated with children’s vocabulary and problem behavior, respectively, the modest

Early Child Care 697

magnitude of all effect sizes involving child care cannot be ignored. Even though there are certainly grounds for questioning the developmental signifi- cance of the enduring ‘‘effects’’ detected, we regard them as noteworthy and meaningful because of the large number of children in America who experience extensive and/or low-quality child care before school entry. This contemporary situation raises questions about the potential collective consequen- cesFacross classrooms, schools, communities, and society at largeFof small enduring developmental differences among children who vary in their early child-care experience (Belsky, 2001; NICHD SEC- CYD, 2003a, 2006). What happens if early child care affects many children in small ways? Do teachers provide higher or lower levels of instruction, spend more or less time managing their classes? Are play- grounds more or less friendly places in which to spend time? To address these issues, future research will need to focus on classroom and playground dynamics instead of focusing solely on individual child outcomes.

In addition to revealing two associations between child-care experience and child development that endured over time, the results also indicated, as al- ready noted, that some previously detected relations became weaker across the elementary school years. In particular, relations linking more time spent in any kind of child care to somewhat higher levels of behavior problems, which had been evident before school entry and in kindergarten and first grade, attenuated, and were no longer statistically signifi- cant in fifth (or even third) grade. The same was true with respect to links between amount of care and teachers’ reports of conflicted relationships with the study children and between quality of care and reading skills. Caution seems warranted before concluding definitively that these earlier detected associations have permanently disappeared, how- ever, if only because at earlier developmental periods we found that significant relations between child care and child development that had seemingly disappeared subsequently re-emerged (NICHD Early Child Care Research Network, 2003a). More- over, developmental theorists have posited that im- portant transitions, such as beginning a new school, entering puberty, or dealing with adolescence, more generally can create challenges in which ‘‘old’’ issues are resurrected (Caspi, 1998). The fact that transition to middle and high school results in less teacher oversight and support for academic achievement, creating challenges for youths who require more scaffolding to maintain their academic achievement (Roeser, Eccles, & Sameroff, 2000), raises the prospect

that relations between child care and child devel- opment that were present early, then disappeared by the late-elementary-school years, could re-emerge in adolescence. At the same time, it must be acknowl- edged that even the small associations that endure to sixth grade may themselves attenuate to the point of becoming nonsignificant or, if they remain, be of no functional significance to children’s development, either in terms of individual functioning or the functioning of groups of children. Examination of social and academic functioning in middle school and high school, therefore, represents an important next step in understanding the relations between child care and developmental outcomes.

One new relation between early child care and children’s development, representing a possible ‘‘sleeper effect,’’ emerged in this inquiry. Children whose child-care hours increased between 3 and 54 months of age scored somewhat lower on vocabu- lary in fifth grade. This is the first time that a link has been detected between the amount of care and aca- demic functioning (or cognitive functioning more generally) in the NICHD SECCYD. This fact, coupled with the findings from the follow-up analyses, showing the effect in question was an apparent ar- tifact of other factors leads us not to offer an expla- nation of it.

Associations linking child-care experience with child development in the late-elementary-school years were smaller in size and less pervasive than those associated with families and parenting (see Table 6, bottom subsection). This is not surprising not only because such results are consistent with earlier study findings but because children are being studied 6 – 7 years after leaving child care for ele- mentary school. Most of the study children were enrolled in more than one child-care setting before they started school and experienced multiple differ- ent classrooms and after-school arrangements sub- sequent to school entry. On average, in fact, study children experienced more than five different care arrangements between 3 and 54 months of age and six different classrooms between kindergarten and fifth grade. In comparison, family experiences and parenting were relatively stable. Parents and chil- dren also share genes, further contributing to the relative strength of associations between parenting and child functioning through sixth grade.

Presuming, as seems likely, that links between parenting quality and child development are not entirely a function of shared biology, the parenting results emerging from this study of child care high- light the potential for interventions aimed at en- hancing parenting to yield greater developmental

698 Belsky et al.

benefits for children than ones geared toward mod- ifying child care, perhaps by improving child-care quality. It is probably misguided, however, to pit these two intervention strategies against one another, especially because efforts made to enhance the quality of parenting do not preclude efforts to modify the child-care experience. Moreover, syner- gistic effects may emerge when both avenues of in- tervention are pursued simultaneously (Love et al., 2005).

Despite the many strengths of the NICHD SEC- CYDFincluding a large, diverse sample, a pro- spective longitudinal design, a rich array of measures obtained from multiple methods, and multiple respondentsFit has limitations. The sam- ple was not specifically drawn to be nationally rep- resentative. Also, the study design is correlational; therefore, causal inferences can only be drawn with caution, if at all. Furthermore, and as already noted, the study only addresses relations between child care and child development at the level of individual children, not potentially cumulative effects on larger social groupings of children. Nonetheless, the re- peated comprehensive measurements of environ- mental contexts of child care, school, and family in conjunction with repeated assessments of both cog- nitive and social functioning have provided a unique opportunity to address the issues of potentially en- during or dissipating effects of early experience after taking into consideration many confounding and competing explanatory factors. The NICHD Early Child Care Research Network continues to monitor the study children’s development into middle ado- lescence to determine whether experiences in early child care (its quality, quantity, or type) relate to academic performance in high school and whether the behavior problems associated with early center care presage problem behaviors in high school.

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