Measuring Infants' Home Environment: The IT-HOME

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... assessed at 3 years of age with the Stanford-Binet Intelligence Scale Form L-M, 3rd Edition (Terman & ... Merrill, 1972). Higher scores on the Stanford-Binet ...
PARENTING: SCIENCE AND PRACTICE Copyright © 2004, Uwrence Erlbaum Associates, Inc. April-September 2004 Volume 4 Numbers 2 and 3 Pages 115-137

Measuring Infants' Home Environment: The IT-HOME for Infants Between Birth and 12 Months in Four National Data Sets Miriam R. Linver, Anne Martin, and Jeanne Brooks-Gunn SYNOPSIS Objective. This article examines new conceptually derived subscales for the Infant-Toddler Home Observation for Measurement of the Environment (ITHOME) Inventory. Design. Data from 4 diverse national longitudinal data sets were used to assess several newly created subscaies: the Infant Health and Development Program {N = 872), the National Institute of Child Health and Human Development Study of Early Child Care (JV = 1,279), the National Longitudinal Survey of Youth (N = 2,374), and the Project on Human Development in Chicago Neighborhoods (N = 258). Validity and reliability of the newly created subscales were assessed. Results. In total, 7 new subscales emerged. Analyses demonstrate overall consistency in validity and reliability of these subscales. Conclusions. Although both observational and self-report items were included in analyses, observational items were in the majority. Researchers are encouraged to include observational items in future implementations of the IT-HOME. If designers of large-scale surveys find the cost of training observers to administer the IT-HOME prohibitive, they should consider selecting subscales rather than the entire Inventory.

INTRODUCTION In this article, we examine the Infant-Toddler Home Observation for Measurement of the Environment Inventory (IT-HOME; Caldwell & Bradley, 1984). We use four data sets that include infant populations in which the IT-HOME was administered when children were < 1 year of age; the Infant Health and Development Program (IHDP), the NICHD Study of Early Child Care (NICHD-SECC), the 1979 National Longitudinal Survey of Youth-Child Supplement (NLSY-CS), and the Project on Human Development in Chicago Neighborhoods (PHDCN). We develop seven subscales

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based on their conceptual coherence that describe infants' home environments. By examining the psychometric properties of these subscales in four large national data sets, we assess their overall utility and robustness and detect patterns in their behavior relative to outcome variables that may be generalizable to other infant populations. Many researchers have examined statistical properties of the IT-HOME, both for the total score and for the six original subscales (listed in Table 1 in the first article in this Special Issue). Bradley and colleagues (Bradley, Mundfrom, Whiteside, Casey, & Barrett, 1994; Bradley, Rock, Caldwell, & Brisby, 1989; Mundfrom, Bradley, & Whiteside, 1993) have examined the original six IT-HOME subscales, which were derived via factor analysis across diverse populations. Eive of the original six subscales emerged with stable factor loadings across a diverse sample of European American, African American, and Latin American low birth weight (< 2500 g) infants from the IHDP data set (Mundfrom et al, 1993). When this same sample was divided by ethnicity, similar factor-analytic patterns emerged for European Americans (five factors accounted for 76.4% of the variance) and African Americans (five factors accounted for 84.9% of variance), but more differences emerged in subscales for the Latin American group (Bradley et al., 1994). With slight modifications in scoring, the IT-HOME demonstrated similar factor loadings for a sample of 99 children with various handicaps (Bradley et al., 1989). Cronbach's alpha levels for the six subscales ranged from .50 to .75, and the alpha level for the total scale was .89. These alpha levels were roughly equivalent to the norm group reported in the original manual (Caldwell & Bradley, 1984). Other researchers have used the IT-HOME as a predictor, correlate, or outcome in analyses. Across studies, the IT-HOME total score is consistently correlated with child cognitive ability and is sometimes found to be associated with maternal characteristics as well. Thompson and colleagues (Thompson et al., 1998) found that, for African American very low birth weight infants, the Parental Involvement IT-HOME subscale was related to cognitive functioning at age 15 months, and the Parental Warmth subscale was related to 24-month cognitive functioning for European Americans. Hoiditch-Davis and colleagues (Holditch-Davis, Tesh, Goldman, Miles, & D'Auria, 2000) reported IT-HOME subscale means for a small (N = 60) sample of medically compron:iised infants as similar to or slightly lower than other normative infant samples. This group found modest correlations of the 6- and 12-month IT-HOME total and subscales with the Bayley scale of cognitive development at 15 months. Murray and Yingling (2000) found that the total IT-HOME score measured at 9 months was correlated with expressive verbal ability at 24 months of age in a sample of medially high-risk infants. Luster and colleagues (Luster, Perlstadt, McKin-

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ney, Sims, & Juang, 1996) noted that in a sample of 83 teenaged mothers the total IT-HOME correlated with contemporaneous infant, mother, and neighborhood characteristics. As reviewed earlier, most researchers have explored the IT-HOME using small samples of medically or otherwise disadvantaged infants and their families; few if any researchers have exaniined the IT-HOME in large-scale surveys with nationally representative populations. In addition, even though researchers have explored the IT-HOME total score and original six subscales, no one has attempted to create new subscales that are conceptually meaningful. The subscales are important because they point to the distinct features of the home environment that influence particular aspects of child development. If, for example, a correlation is found between the IT-HOME total score and a child outcome (e.g., Bayley cognitive score), without subscales it is difficult to determine what about the home environment serves as the pathway of influence. The seven subscales of the IT-HOME proposed here are Parental Lack of Punitiveness/Hostility, Parental Support of Learning and Literacy, Parental Warmth, Parental Verbal Skills, Encouragement of Developmental Advance, Interior of Home, and Exterior of Home. Eor these analyses, not all subscales are included in all data sets due to availability of items. In the following section, we describe each data set's sample and measures in some detail. In addition, we discuss the IT-HOME subscales created within each data set and the results of reliability analyses, including Cronbach's alpha computations and validity analyses, including zero-order and partial Pearson's correlations with children's outcomes at age 3.

METHODS

In this section, we describe the sample and measures in all four data sets used in this study: IHDP, NLSY-CS, NICHD-SECC, and PHDCN. Please refer to the first article in this Special Issue for a description of each data set's study design. Samples The Infant Health and Development Project Subsawple. The subsample of the IHDP selected for this study includes those with no missing data on any IT-HOME items or child outcomes (N = 872). Thirty-nine percent of this subsample participated in the intervention; 61% were follow-up only. All children were 12 months old when the

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IT-HOME was administered. The sample was approximately evenly split between girls and boys; about half the sample was African American, about 40% were European American, and about 10% were of other ethnicity (Table 1). Twenty-three percent of mothers were less than 20 years old at the time of their child's birth. The IHDP sample is fairly disadvantaged, with 38% receiving welfare at child's age 1; 40% of the sample had less than a high school education, 27% had a high school degree, and 33% had some college or more education. About half (47%) were unmarried at the birth of the child. (See Brooks-Gunn, Duncan, Klebanov, & Sealand, 1993; Duncan, Brooks-Gunn, & Klebanov, 1994, for comparisons of IHDP demographics with nationally representative data sets.)

Measures. In the IHDP, the IT-HOME Inventory was administered through observation and a semistructured interview during the 1-year home visit; all 45 items in the original IT-HOME (Caldwell & Bradley, 1984) were assessed. It took approximately 1 hr to administer. Each item was coded dichotomously (yes/no). The first outcome, cognitive ability, was assessed at 3 years of age with the Stanford-Binet Intelligence Scale Form L-M, 3rd Edition (Terman & TABLE 1

Demographic Characteristics of Study Samples

Child is male (%) Mean child age, months Race/ethnicity of mother (%) European American African American Other Mothers < 20 at birth (%) Mother's education at birth (%) Less than high school (< 12} High school degree (= 12) Some college (13+) Mother married at birth (%) Receiving welfare al birth (%)

PHDCN (N = 258)

IHDP (N = 872)

53 5.1

49 12.0

52 6.0

53 6.3

20 24 56^ 17

37" 53

58

10

84 12 4

23

6

44

39 28

9 21 70 87

41 73

26^

24

14 42 57 40

33

47

NICHD-SECC (N= 1,279)

NLSY-CS (N = 2,374)

26 16 0 16

43

Note. N/A = not applicable, ^IHDP classified European American and Asian American ethnicities together. '^PHDCN classified Latin Americans as "other race/ethnicity," '^Measured at age 1, '^NICHD-SECC captured the income value of a family's benefits from all public assistance programs at 1 and 6 months after the child's birth. An indicator variable was created to reflect whether the family ever received benefits with any income value by the 6th month after the child's birth.

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Merrill, 1972). Higher scores on the Stanford-Binet indicate greater cognitive ability {standardization sample mean of 100, SD = 15). The mean cognitive ability score at age 3 years was 88 {SD = 20; range = 43-147); this relatively low score was expected, given that the sample was composed of low birth weight, premature children (Drillien & Drummond, 1977; McCormick et al., 1992), many of whom were poor {Phillips, Brooks-Gunn, Duncan, Klebanov, & Crane, 1998; Ramey & Ramey, 1998). The second outcome, behavioral competence, was assessed at age 3 with the Child Behavior Checklist (CBCL) for Ages 2-3 (Achenbach, Edelbrock, & Howell, 1987), comprised of 99 items where mothers responded on a 3-point scale {0 = not at all true, 1 = sometimes true,1 = often frwe). The responses were then dichotomized {0 = not at all true, 1 = sometimes/often true)

and summed to form the CBCL scale. Previous research indicates that the CBCL shows good test-retest reliability and concurrent and predictive validity; it discriminates between clinically referred and nonreferred toddlers, and it predicts problem scores over 3 years (Achenbach et al., 1987). Higher scores on the CBCL indicate more child behavior problems. The mean score on the CBCL was in the expected range (M = 45.98, SD = 20.18, range = 3-121; Achenbach & Edelbrock, 1981; Achenbach et al., 1987; Brooks-Gurm, Klebanov, Liaw, & Spiker, 1993; McConaugbty & Achenbach, 1988). The NICHD Study of Early Child Care Subsample. The subsample of the NICHD-SECC selected for tbis analysis consists of 1,279 children who had no missing data for either the IT-HOME or the child outcome measures. About half the sample were boys {Table 1), and the majority of mothers were European American {84%), who were married at the child's birth {87%) and had some college or more educational achievement {70%). Only about 7% of mothers were less than 20 years old when their child was bom, and about one fourth had ever received welfare by the time their child was 6 months old. Measures. Ail 45 items from the original IT-HOME were collected during home visits when the child was 6 months old by direct observation and a semistructured interview with the mother. Training and certification with both videotapes and live observations were utilized to establish the interobserver reliability on the IT-HOME. All observers maintained 90% agreement with a master coder. Several cognitive outcome measures are available in the NICHD-SECC data set- Tbe earliest available cognitive outcome is the Bayley Mental Development Index {MDI) at 15 months. Tbe MDI, part of the Bayley Scales of

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Infant Development {Bayley, 1969,1993), is the single most widely used measure of cognitive development for children in the first 2 years of life. It assesses sensory perceptual acuity and discrimination; memory, learning, and problem solving; early verbal communication; and the ability to form generalizations and classifications. The original version of the Bayley {1969} was administered at 15 months. In the NICHD-SECC sample, the mean score on the MDI at month 15 is 108.65 {SD = 14.05). Children's behavioral problems were assessed at age 24 months with the CBCL for Ages 2-3 {Achenbacb et al., 1987). Mothers were asked to rate 99 items about how true characteristics of the child's behavior were over the last 2 months. As in the IHDP, the 3-point Likert responses were dichotomized and summed to form the CBCL scale. In our sample, the mean score on the CBCL at 24 month is 36.25 {SD = 17.51; range = 2-119).

National Longitudinal Survey of Youth-Child Supplement {NLSY-CS) Subsample. As of 1998, a total of 10,918 children were identified as baving been born to the original women in the NLSY Youth sample. All children were automatically enrolled in the Child Supplement (CS). Because information on children was not collected until 1986, we exclude those born before tbat year. In addition, NLSY-CS first assesses children's cognitive and behavioral outcomes when tbey turn 3 years old; thus, the infant cohort from year 1994 is the most recent sample for whom cognitive and behavioral outcomes are available for analyses. Therefore, the NLSY-CS cohorts included in this subsample are the 1986,1988,1990,1992, and 1994 cohorts. We further select children with no missing data on tbe IT-HOME or either outcome {N = 2,374). The NLSY-CS subsample in this study represents children born between 1986 and 1994 to a nationally representative sample of women aged 14 to 21 in 1979. These women ranged in age from 20 to 37 at the time of the study child's birth. Consequently, our subsample omits the children of relatively old mothers {Chase-Lansdale, Mott, Brooks-Gunn, & Phillips, 1991). As listed in Table 1, about half of tbe children are boys, 60% are European American, 26% are African American, and 16% are of other ethnicity. Sixteen percent of tbe mothers had not completed high school, 43% had a high school degree, and 41 % went beyond high scbool. Just over 70% of the mothers were married when their child was born, and one fourth of the mothers were receiving welfare at their child's birth. Because we excluded children born before 1986, no mothers were teens when their child was born.

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Measures. The NLSY-CS adopted the Home Observation for Measurement of the Environment—Short Form (HOME-SF; Center for Human Resource Research, 1998) as the primary measure of the quality of a child's home environment. The HOME-SF, developed in consultation with Caldwell and Bradley {Center for Human Resource Research, 1998), is a shorter version of the HOME and, like the original, varies hy age group (infant, toddler, school-age, early adolescent). The IT-HOME-SF is about half as long as the original IT-HOME (18 items, compared to 45). More than half the items are assessed from maternal report, and many items have been reworded from the original dichotomous responses into multiple choice responses. The HOME-SF scales included in this article were collected when NLSY-CS children were between 1 and 12 months of age. Prior to constructing subscales for the IT-HOME-SE, all items were transformed into dichotomous variables (Center for Human Resource Research, 1998). In the NLSY-CS, the IT-HOME-SF contains only two subscales: Cognitive Stimulation and Emotional Support. Numerous previous studies have demonstrated that the total HOME-SF, as well as the Cognitive Stimulation and Emotional Support subscales, have good reliability, construct validity, and predictive validity (Cooley & Unger, 1991; Klebanov, Brooks-Gunn, Chase-Lansdale, & Gordon, 1997; Moore & Snyder, 1991). However, these subscales were bypassed in this study in favor of the new conceptually derived ones. The cognitive outcome used to test the predictive validity of the proposed subscales in the NLSY-CS sample is the Peabody Picture Vocabulary Test—Revised (PPVT-R), collected at age 3. This test assesses vocabulary knowledge in children aged 3 years and older (Dunn & Dunn, 1981; Phillips et al., 1998). It consists of 175 vocabulary items of increasing difficulty. For each word read out loud by the assessor, the child points to one of four pictures that best describes its meaning. In 1986, this assessment was only given in English. Beginning in 1988, a Spanish version of the assessment was administered when required. Numerous studies have demonstrated that the PPVT-R has good test-retest reliability and construct and predictive validity (Dunn & Dunn, 1981; Goldstein, Collier, Dill, & Tilis, 1970). In our NLSY-CS sample, the mean raw score of the PPVT-R for the infant cohort at age 3 is 46.27 (SD = 21.86). The behavior outcome used to test the subscales' validity is the Behavior Problems Index (BPI), which measures the frequency, range, and type of childhood behavior problems for children age 4 and older (Peterson & Zill, 1986). Many items included in the BPI were drawn from the Child Behavior Checklist (Achenbach, 1991) and other child behavior scales (Graham & Rutter, 1968; Kellam, Brach, Agrawal, &: Ensminger, 1975; Rutter, Tizard, & Whitmore, 1970). It consists of 28 items (two are appropriate only for chil-

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dren who attend school) describing behavior problems. Mothers are asked to rate each item according to how characteristic it was of the child in the previous 3 months (0 = not true, 1 = sometimes true, 2 = very true). For this

study, responses to the individual items were dichotomized (0 = not true, 1 = sometimes true/very true) and summed to produce an index for each child. Higher scores represent a greater level of behavior problems. Previous research indicates that the BPI shows good reliability and construct validity (Parcel & Menaghan, 1988a, 1988b). In our sample, the mean standard score on the BPI at age 3 is 102.90 (SD = 14.95). Project on Human Development in Chicago Neighborhoods Suhsample. This study uses data on a subset of the birth cohort, a string of consecutive enrollees at wave 1 in 1995 who participated in an intensive substudy of infants (JV = 413). These infants and their families were administered an expanded developmental battery in addition to the standard protocol. Selecting children with no missing HOME or outcome data yielded a sample of 258 children. On average, infants were 5 months old, and 54% were male (Table 1). The infants were distributed across racial/ethnic groups (20% European American, 24% African American, and 56% Other), and a range of socioeconomic groups were represented by design. Eorty-four percent of the infants' mothers did not graduate from high school, 14% completed high school, and 42% went beyond high school. Eewer than half (43%) of the infants' mothers were unmarried, and 17% were teenagers at the time of their child's birth. Forty percent of the children's families received public assistance in the last year. Measures. During the first wave of data collection, the IT-HOME was administered during home visits to all families with children included in the infant substudy. Eleven of the original 45 items were omitted because they were not relevant for children several months old. The content of the IT-HOME was further revised to include 18 additional items from other age versions of the IT-HOME, deemed age appropriate for this cohort, to increase comparability of measurement for children of different ages (Leventhal, Selner-O'Hagan, Brooks-Gunn, Bingenheimer, & Earls, this issue). Finally, the IT-HOME was augmented with eight items from the PHDCN's Systematic Social Observation instrument, which captures the immediate external environment of the home (Barnes-McGuire & Reiss, 1993). Therefore, there was a total of 57 items in all A more structured format than the standard semistructured interview was developed to facili-

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tate data collection, and the training manual was adapted to include more specific examples for coding each item than provided in the original manual (Selner-O'Hagan & Kupstas, 1995). Children's behavior problems were assessed in 1998, at wave 2 (when the children were 3), using the Reduced Child Behavior Checklist. This scale includes 35 items selected from the BPI {Zill, 1985) and the CBCL (Achenbach et al., 1987) that tap problems of relevance to the larger study. For each item, the primary caregiver reported how true each behavior was of the child during the past 6 months, using a 3-point scale (0 = not true, 1 = sometimes true, 2 = often true). For this analysis, responses were recoded dichotomously to reflect whether the behavior was reported as sometimes or often true (compared with not true). A total raw score was calculated, with higher scores indicating more problems (M = 13.14, SD = 6.45, range = 0-28, o£ = .87). Children's cognitive outcome measures were not collected; thus, cognitive outcomes are not used to test the predictive validity of the proposed IT-HOME subscales in the PHDCN data set. Analytic Strategy Following the technique outlined in the introductory article in this Special Issue, conceptually meaningful subscales were created for the ITHOME in each data set. After reliabiUty statistics were used to finalize the composition of the subscales, we conducted two sets of analyses to investigate the validity of our subscales. We examined how each subscale was related at the bivariate level to child cognitive and behavioral outcomes captured at a later time point (approximately 2 years later). In addition, we considered partial correlations between IT-HOME subscales and child outcomes, controlling for a variety of sample demographics that may have confounding effects, namely, treatment group (for IHDP), child gender, child age (if the children's age varied in the sample), maternal race/ethnicity, teen childbearing, mother's education, marital status, and welfare receipt. RESULTS

Table 2 lists, for each data set, the items included in the IT-HOME and their corresponding subscale. If an item was present in a data set but not included in a subscale, it is listed as N/S (no subscale); if the item was not available in a particular data set, it is listed as N/A (not available). Table 3 presents, for each data set, the properties of each subscale, including the number of items, Cronbach's alpha, scale mean and standard

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ever, there were also several important differences. First, the NLSY-CS data set is the only one of the four that did not include the full IT-HOME scale. Although the subscales proposed here were limited by the availability of far fewer items, they coriformed to our standards for reliability. The three resulting subscales—Parental Warmth, Parental Lack of Hostility, and Support of Learning and Literacy—are comparable to their counterparts in the other three data sets. Another difference across data sets is the presence of a Developmental Advance subscale in IHDP alone. All items in this subscale are subsumed in the Support of Learning and Literacy subscale in the NICHD-SECC data set, because the alpha level was not sufficient in the NICHD-SECC to include as a separate subscale. In the PHDCN data set, the Developmental Advance subscale did not have an adequate alpha level and was therefore dropped. Finally, the PHDCN includes two subscales—Interior and Exterior of the Home—not included in the other studies, as additional items were available in the PHDCN data set only. As shown in Table 3, subscales included from 2 to 16 items. Most subscale statistics met our internal reliability requirements of item-to-scale correlations of .25 or higher, and a minimum Cronbach's alpha level of .50. There were some exceptions to these cutoffs in instances when a particular item was included because it was deemed conceptually relevant to a subscale. Associations Between Subscales and Child Outcomes We generated zero-order and partial Pearson correlations of IT-HOME subscales with later child cognitive and behavioral outcomes. Table 4 presents the correlations with child cognitive outcomes (as noted previously, the PHDCN data set does not contain toddler cognitive outcomes, so this data set does not appear). At the zero-order level, the pattern of results is clear and consistent: nearly all subscales were significantly positively correlated with child cognitive ability across all data sets. However, when sample demographic characteristics were partialed out, differences emerged across the subscales. The Support of Learning and Literacy subscale remained significantly associated with child cognitive outcomes across all data sets. Similarly, the IHDP Developmental Advance subscale also remained significantly associated with child cognitive ability. Parental Warmth remained significantly positively correlated with child cognitive scores in the NLSY-CS, and the correlation approached significance in the IHDP data set as well. However, the correlation was no longer significant in the NICHD-SECC data set. Parental Verbal Skills was no longer significantly correlated with child cognitive outcomes in any data set after demographic characteristics were partialed out. Finally, Parental Lack of Hostility was associated with cognitive outcomes in opposing directions of

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small but equal magnitude in the NICHD-SECC and the NLSY-CS. It was no longer significantly correlated with cognitive ability in IHDR The correlational analyses of IT-HOME subscales with behavior problems outconies, presented in Table 5, demonstrated a relatively weak relation of the HOME with behavior problem outcomes, after controlling for sociodemographic characteristics. In the PHDCN data set, no early ITHOME subscales were correlated with later behavioral problem scores, even in a bivariate context. In the IHDP and NICHD-SECC data sets, nearly all the IT-HOME subscales were correlated with behavior problem scores at the zero-order level. When sample demographic characteristics were partialed out, in the NICHD-SECC data set the correlations between IT-HOME subscales and behavior problem scores were no longer significant. In the IHDP data set, one correlation remained significant: a negative correlation between the Lack of Hostility subscale and child behavior problems. In addition, the negative association of behavior problems with the Developmental Advance subscale approached significance. Finally, in the NLSY-CS data set, the Support of Learning and Literacy subscale remained significantly negatively correlated with behavior problems, even after demographic characteristics were partialed out; the size of this correlation, however, was quite small.

DISCUSSION Our analyses of IT-HOME subscales across four data sets—IHDP, NICHDSECC, NLSY-CS, and PHDCN—lead us to several conclusions. First, we established the reliability of seven conceptually developed subscales, many with similar items across data sets. Given this evidence, these newly developed subscales offer an advantage over using the full IT-HOME or factor-analysis derived subscales. They are focused in content and may allow very specific hypotheses about the home environment to be tested. As an example, one could examine the unique role of infants' supportive learning and literacy environment versus infants' nonpunitive environment in assessing later childhood developmental outcomes. The original factor-analysis derived subscales had some items that were extraneous to the "theme" of the subscale. For example, with the nonpunitive envirorunent subscale, in addition to items that assessed harshness (or lack thereof) during the home visit as well as in the recent past, two other items are included: "at least 10 books are present and visible" and "family has a pet." The revised subscales, however, do not contain such unconnected items. Second, we found mixed evidence for validity using these conceptually derived IT-HOME subscales. The Support of Learning and Literacy and Parental Warmth subscales worked best for the cognitive outcomes across

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