Home literacy environment of pre-school children withintellectual disabilitiesjir_1222 1..14

M. van der Schuit,1 M. Peeters,1 E. Segers,1 H. van Balkom2 & L. Verhoeven1

1 Department of Special Education, Behavioural Science Institute, Radboud University Nijmegen, Nijmegen,The Netherlands2 Research Centre on Atypical Communication, Radboud University Nijmegen, Nijmegen,The Netherlands

Abstract

Background For pre-school children, the home lit-eracy environment (HLE) plays an important rolein the development of language and literacy skills.As there is little known about the HLE of childrenwith intellectual disabilities (ID), the aim of thepresent study was to investigate the HLE of chil-dren with ID in comparison with children withoutdisabilities.Method Parent questionnaires concerning aspectsof the HLE were used to investigate differencesbetween 48 children with ID, 107 children withoutdisabilities of the same chronological age and 36

children without disabilities of the same mental age(MA). Furthermore, for the children with ID, corre-lations were computed between aspects of the HLEand children’s non-verbal intelligence, speech intel-ligibility, language and early literacy skills.Results and conclusions From the results of the mul-tivariate analyses of variance it could be concludedthat the HLE of children with ID differed from thatof children in the chronological age group onalmost all aspects. When compared with children inthe MA group, differences in the HLE remained.

However, differences mainly concerned child-initiated activities and not parent-initiated activities.Correlation analyses showed that children’s activi-ties with literacy materials were positively relatedwith MA, productive syntax and vocabulary age,and book orientation skills. Also, children’s involve-ment during storybook reading was related withtheir MA, receptive language age, productive syntaxand vocabulary age, book orientation and rapidnaming of pictures. The amount of literacy materi-als parents provided was related to a higher produc-tive syntax age and level of book orientation of thechildren. Parent play activities were also positivelyrelated to children’s speech intelligibility. The cogni-tive disabilities of the children were the main causeof the differences found in the HLE between chil-dren with ID and children without disabilities.Parents also adapt their level to the developmentallevel of their child, which may not always be themost stimulating for the children.

Keywords early literacy, home literacyenvironment, intellectual disability, language,pre-school

Children with intellectual disabilities (ID) areknown to be at risk for limited language and lit-eracy development (Kaiser et al. 2001; Abbedutoet al. 2007). The group is characterised by largevariation in kind and severity of the disabilities, but

Correspondence: Ms Margje van der Schuit, Behavioural ScienceInstitute, Radboud University Nijmegen, Department of SpecialEducation, room A. 05.17, Montessorilaan 3/P.O. Box 9104, 6500

HE Nijmegen, The Netherlands (e-mail: m.vanderschuit@pwo.ru.nl).

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in the vast majority of cases their ID are accompa-nied by speech and/or language disabilities. Thesechildren develop language slower than typicallydeveloping children, but seem to follow the samedevelopmental steps (Bates et al. 1995), thus havinglanguage abilities that are at the level of theirmental age (MA) (Chapman 1997; Rondal 2001).Besides cognitive and speech disabilities, the homeliteracy environment (HLE) may also play animportant role in their language and literacy devel-opment (Weikle & Hadadian 2004).

Children develop their early language and literacyskills in the context of their HLE (Scarborough &Dobrich 1994; Whitehurst & Lonigan 1998). TheHLE is seen as a construct that consists of variousinterrelated aspects, all influencing the languageand literacy development of children (Leseman &de Jong 1998; Roberts et al. 2005). Some aspectsare: shared storybook reading and the amount ofactive engagement of the child during this activity(Justice & Kaderavek 2002), literacy interest of thechild (Frijters et al. 2000), the number of readingand writing materials available (Hood et al. 2008),the experiences and activities of the child with lit-eracy materials (Levy et al. 2006), activities ofparents to stimulate children’s literacy development(Sénéchal & LeFevre 2002; Wood 2002), parents’own literacy materials and activities (Foy & Mann2003), the attitudes and beliefs of parents about theimportance of early literacy exposure (Weigel et al.2006a), and the expectations of parents regardingtheir child’s literacy development (Lee & Groninger1994).

Much research on the HLE of children with dis-abilities focused on children with physical disabili-ties (e.g. cerebral palsy) (Light & Kelford Smith1993; Dahlgren Sandberg 1998). It was shown thatthese children have limited access to literacy materi-als (i.e. books, drawing materials) and have feweropportunities to interact with these materials inde-pendently than their peers without disabilities(Light & Kelford Smith 1993; Peeters et al. inpress). Furthermore, in contrast to parents of chil-dren without disabilities, parents of children withphysical disabilities mostly dominate the interactionduring storybook reading, giving the child feweropportunities to actively participate in the conversa-tion. This leads to fewer initiations and morepassive responses with yes/no answers of the child

(Light et al. 1994; Dahlgren Sandberg 1998; Peeterset al. 2009). The differences that were foundbetween the children with cerebral palsy and chil-dren without disabilities could largely be explainedby the physical and accompanying disabilities of thechildren and not by differences in intellectualcapacities. Previous studies indicate that for chil-dren with ID, the HLE is different from that oftypically developing children (Weikle & Hadadian2004). These children have fewer literacy materialsto interact with than their peers without ID(Marvin 1994; Trenholm & Mirenda 2006), areread to less frequently, and during storybookreading interactions, the main behaviours of theirparents are pointing to and/or labelling pictures.Higher-order reading interactions, like asking whatwould happen next or to retell a story, are less fre-quently used during storybook reading (Trenholm& Mirenda 2006).

The research described above mostly containedgroups of children with disabilities that were eitherhighly heterogeneous in both age and disability (cf.Marvin 1994; Weikle & Hadadian 2003) or focusedonly on a very specific subgroup of children, likechildren with Down’s syndrome (Trenholm &Mirenda 2006). While early literacy skills are impor-tant predictors of later reading development(Sénéchal & LeFevre 2002), no research has beencarried out on pre-school children with ID. Fur-thermore, no studies have investigated whether theHLE of children with ID differed from childrenwithout disabilities with the same MA, thus ignor-ing the fact that lower developmental age mayexplain the differences found between the HLE ofchildren with and without disabilities of the samechronological age (CA).

In the present study, we therefore compared pre-school children with ID with two comparisongroups of children without disabilities: one compa-rable on CA and one comparable on MA. Also,taking into account the heterogeneity of the IDgroup, the relationships between aspects of theHLE and children’s non-verbal intelligence, speechintelligibility, language and early literacy skills wereexamined. The following research questions wereaddressed:1 What and of what nature are the differencesbetween the HLE of children with ID and CA com-parison children without disabilities?

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2 What and of what nature are the differencesbetween the HLE of children with ID and MAcomparison children without disabilities?3 Within the group of children with ID, to whatextent do relationships exist between aspects of theHLE and children’s non-verbal intelligence, speechintelligibility, language and early literacy skills?

With regard to the first question, we expected theHLE of children with ID to be both quantitativelyand qualitatively different from the HLE of theirpeers without disabilities, because children with IDwill probably have fewer opportunities to manipu-late books and writing materials independently andto be less actively engaged during storybook reading(cf. Marvin 1994; Marvin & Wright 1997; Trenholm& Mirenda 2006; Peeters et al. in press). We alsoexpected parents of children with ID to engage lessfrequently in emergent literacy activities with theirchildren and to have lower expectations for theirchild’s literacy development. Regarding the secondresearch question, differences were expectedbetween children with ID and children without dis-abilities of the same MA. These differences wereagain expected to be found in the child’s ownactivities with literacy materials, but not in theactivities parents provided to stimulate their child’sliteracy development, as parents are known to adapttheir communication to the developmental level oftheir child (Kaiser et al. 2001). Concerning thethird question, the expectation was that children’snon-verbal intelligence, speech intelligibility, lan-guage and early literacy skills were all related insome way to one or more aspects of the HLE, giventhat these relationships were previously found intypically developing children (Frijters et al. 2000;Weigel et al. 2006b). For example, children’s knowl-edge about features of printed language (i.e. bookorientation) was expected to be related with the lit-eracy materials parents provided for their children(Weigel et al. 2006b).

Method

Participants

Participants were pre-school children with ID, CAcomparison children without disabilities and MAcomparison children without disabilities.1 Parents orguardians of all children gave informed consent at

study entry. Parents of 48 children with ID (64% ofapproached parents), 107 CA comparison childrenwithout disabilities (85%) and 36 MA comparisonchildren without disabilities responded to the ques-tionnaires (76%).

The children with ID attended special day-carecentres and schools for pre-school children with IDin the Netherlands. Inclusion criteria for these chil-dren were: a CA between 3 and 5 years, a non-verbal IQ between 50 and 85, no severe hearing orvision loss and Dutch as the primary language athome. This group consisted of 35 boys and 13 girls(IQ range 49–84, M = 58, SD = 9.88): 5 with Downor another syndrome, 10 with an accompanying dis-order like autism or attention deficit hyperactivitydisorder, 4 with brain damage or epilepsy, 2 withdyspraxia, 2 with a sensory impairment, 3 with apsychomotor retardation and 22 with a yetunknown aetiology of their ID. Parents of 27 chil-dren reported their child to use symbols besides orinstead of natural speech to communicate; 12 ofthese children had access to these symbols duringstorybook reading.

The children without disabilities were recruitedfrom regular day-care centres and schools in theNetherlands. These children had a CA between 3

and 5 years, had no known impairments and Dutchas the primary language at home. The CA groupconsisted of 52 boys and 55 girls. The MA groupconsisted of 19 boys and 17 girls. Eleven children(six boys and five girls) with a very low MA (below29 months) were removed from the ID group inorder to make the ID group comparable on MA tothe MA group. The characteristics of the ID, CAand MA groups used in the analyses can be foundin Table 1.

Materials

The materials used in this study consisted of fiveparent questionnaires regarding the HLE and sevenstandardised tasks to assess children’s non-verbalintelligence, speech intelligibility, language and earlyliteracy skills.

Home literacy environment parent questionnaires

We used the five HLE parent questionnaires fromPeeters et al. (2009) and Peeters et al. (in press)

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addressing: (1) child’s literacy interest; (2) child’sactivities during storybook reading; (3) materialsand parental activities for child literacy develop-ment; (4) parents’ own literacy materials and activi-ties; and (5) parents’ expectations of their child’sliteracy development.

For the first four questionnaires, factor analyseswere performed using Principal Axis Factoring withpromax rotation (cf. Peeters et al. 2009; Peeterset al. in press). The individual items of the fourparent questionnaires and the results of the factoranalyses can be found in Appendix 1. The results ofthe factor analyses were comparable to Peeters et al.(in press), indicating that the questionnaires werereliable and valid measurements of the HLE.

The fifth questionnaire consisted of two multiple-choice items concerning parents’ expectations abouttheir child’s literacy development (i.e. reading andwriting levels) at the end of elementary school, i.e.,the end of sixth grade. These items were analysedwith c2-tests.

Standardised tasks

Intelligence

Non-verbal intelligence was measured by adminis-tering the Revised Snijders–Oomen Non-verbalIntelligence Test (SON-R 2.5–7) (Tellegen et al.2005), a standardised test (Cronbach’s

alpha = 0.90) that measures non-verbal intelligencewithout using spoken or written language. The testis divided in a reasoning scale (situations, categoriesand analogies) and a performance scale (patterns,mosaics and puzzles). The six subtests are com-posed of 14–17 items with an increasing level of dif-ficulty. For the reasoning score the reliability has amean value of 0.84 and the reliability of the perfor-mance score is on the average 0.85.

Speech intelligibility

In a pseudo word articulation task (Verhoeven2006; Cronbach’s alpha = 0.95.), the child wasinstructed to repeat 40 pseudo words of increasingdifficulty. Words were presented one at a time by arecorded voice. The task was terminated when thechild had made five successive errors.

Receptive language

Receptive language was assessed by the Dutchversion of the Reynell Test for Language Compre-hension (Van Eldik et al. 2004; Cronbach’salpha = 0.90), a standardised test designed tomeasure language comprehension (passive vocabu-lary and comprehension of grammatical structures)in children from 1.2 to 6.3 years of age. The test isdivided into 12 sections, composed of 3–14 itemswith an increasing level of difficulty.

Table 1 Group characteristics

CA comparison MA comparison

ID (n = 48) CA (n = 107) P ID (n = 37) MA (n = 36) P

CA 54 months (SD = 9.7) 55 months (SD = 2.6) 0.71‡ 58 months (SD = 7.7) 36 months (SD = 1.9) 0.01**‡

MA – – – 38 months (SD = 6.7) 40 months (SD = 5.1) 0.18‡

Gender 35 boys; 13 girls 52 boys; 55 girls 0.01**§ 29 boys; 8 girls 19 boys; 17 girls 0.02*§

SES† 4.7 (range: 1.5–7) 5.0 (range: 2–7) 0.49§ 4.5 (range: 1.5–7) 5.6 (3.5–7) 0.11§

Age of theparent whofilled in thequestionnaire

37.5 years (SD = 5.1) 36.6 years (SD = 4.7) 0.26‡ 38.4 years (SD = 5.2) 37.2 (SD = 2.9) 0.22‡

* P < 0.05, ** P < 0.01.† Based on parental education; 1 = no education, 7 = academic education.‡ Results from t-test.§ Results from c2-test.CA, chronological age; ID, intellectual disability; MA, mental age; SES, social economic status.

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Expressive language

Expressive language was assessed by the SchlichtingTest for Language Production (Schlichting et al.2003). The test is divided into two subtests. Thesubtest for sentence development (Cronbach’salpha = 0.85) measures the productive syntacticdevelopment of children by eliciting syntactic struc-tures of different difficulty (e.g. one-, two- or three-word sentences) from the child through toys andpictures. The subtest for word development (Cron-bach’s alpha = 0.87) measures the productivevocabulary of a child by means of naming concreteobjects and pictures.

Book orientation ( Van Kuyk & Verhoeven 1996;Cronbach’s alpha = 0.80)

On the basis of a book children had to answer 24

questions concerning knowledge about features ofprinted language (e.g. point at the front of thebook, show the reading direction, point to letters).

Auditory discrimination

This task consisted of 3 training and 20 test items(Peeters 2006, unpublished manuscript; Cronbach’salpha = 0.87). Children were presented with twopictures of sound-related, one-syllable words. Theexaminer named the pictures and then asked thechild to point to one of the pictures, thus havingthem discriminate between words like bel [bell] andbal [ball] or nat [wet] and mat [mat].

Rapid naming pictures

A standardised subtest of the Dutch SLI ScreeningTest for Rapid Naming of Pictures was adminis-tered (Verhoeven 2006; Cronbach’s alpha = 0.95).This task consisted of five different pictures (repre-senting a duck, glasses, shoe, house and comb)depicted in four columns of 30 pictures each, yield-ing a total number of 120 pictures. The child wasasked to name as many pictures as fast as possibleand as correctly as possible in a vertical direction(i.e. column by column) during 1 min.

Procedure

The parent questionnaires were sent to the parentsvia the day-care centres or schools, asking the

parent reading most often to the child to fill in thequestionnaires. The child variables were assessed byindividually testing the children during the timethey visited the day-care centre or school. Assess-ments were carried out in a quiet room by aninstructed examiner. The Schlichting Test for Pro-ductive Language was always preceded by theReynell Test for Receptive Language. Instructionswere given verbally, in a non-verbal way by gesturesor a combination of both, depending on the child’scommunicative abilities. For the Non-verbal Intelli-gence Test, instructions were also given throughdemonstration by the examiner. Communicationcould be adapted to the particular child, whichallowed for a natural and stimulating contact.Moreover, after each item the child received feed-back on his or her performance. If necessary, theexaminer demonstrated the correct solution to thechild. For the Reynell Test for Receptive Languageand the Schlichting Test for Productive Language,answers in sign language were accepted.

Age equivalents that corresponded with thechild’s total scores on the tests for non-verbal intel-ligence, receptive language and expressive languagewere obtained by using the norms from the testmanual.

Statistical analyses

After the factor analyses of the parent question-naires were performed, items with salient loadings(>0.30) on the factors were converted to Z-scoresfor all groups. Next, for each factor a compositescore was computed, consisting of the averagedstandard score of the items with salient loadings onthe factor. Cronbach’s alpha values were also calcu-lated for each factor. Then, descriptive statisticswere obtained for all groups, followed by multivari-ate analyses of variance to investigate differencesbetween the ID and CA groups and next betweenthe ID and MA groups. Also, separate compositescores were computed for the children with IDbased on the average Z-scores for the group of chil-dren with ID only. To examine the relationshipsbetween HLE and children’s non-verbal intelli-gence, speech intelligibility, language and early lit-eracy skills, correlations were computed (Pearson)between the composite scores of the factors and thechildren’s test scores.

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Results

Comparison with children without disabilities ofthe same chronological age

The first research question was concerned with thecomparison of the ID and CA groups. Results (seeTable 2) showed an overall effect for group,meaning that there were differences between thetwo groups on aspects of the HLE, Wilks’Lambda = 0.432, F15,139 = 12.19, P < 0.001 andhp

2 = 0.57. No differences between the groups werefound for the factors: parent play activities, parentown book reading, parent magazine reading andparent newspaper reading. The children with IDhad lower scores than the CA group on all otherfactors (P < 0.05), with the exception of book orien-tation. Children with ID seemed to dominate thebook reading interaction more than the CA group.

Parents of children with ID had lower scores onthe factors related to their activities than theparents of the CA group. Regarding parents’ expec-tations for their child’s reading level at the end ofelementary school, again significant differencesbetween the group of children with ID and the CAgroup were found, c2 (5, n = 155) = 93.70, P < 0.001

and eta = 0.74.2 Most parents of children withoutdisabilities had high expectations for their child’sreading level; i.e., they expected their child to beable to read easy texts (6%) or to read books inde-pendently (85%) at the end of elementary school.Only 2% of these parents expected their child to beable to read with pictograms, letters or words, and7% of the parents did not know what to expect fortheir child’s literacy skills at the end of elementaryschool. In contrast, parents of children with IDoften reported that they did not know what toexpect of their child’s future reading level (69%). Ifparents had expectations these were generally lower;i.e., they expected their child to be able to readwith pictograms (11%), letters (2%) or words (6%).Only 4% expected their child to be able to readeasy texts and 8% of the parents expected theirchild to be able to read books independently. Noneof the parents of the children with ID or the CAgroup expected their child not to be able to read atthe end of elementary school.

For the writing levels of the children at the endof elementary school, parents’ expectations showedthe same pattern, c2 (5, n = 155) = 95.80, P < 0.001

and eta = 0.77.2 Parents of children with ID had no

Table 2 Descriptive statistics of the HLE factors for the group of children with ID (n = 48) and the CA comparison group (n = 107)

HLE factors

ID CA

F hp2 PM SD M SD

Child’s writing activities -0.74 0.86 0.33 0.54 87.76 0.37 0.001***Child’s storybook reading interest -0.56 1.07 0.25 0.63 34.50 0.18 0.001***Child’s activities with literacy materials -0.20 0.66 0.09 0.58 7.48 0.05 0.007**Story orientation activities -0.55 0.56 0.25 0.59 63.65 0.29 0.001***Book orientation activities 0.29 0.94 -0.13 0.65 10.63 0.07 0.001***Picture orientation activities -0.34 1.11 0.15 0.67 11.46 0.07 0.001***Word orientation activities -0.43 0.75 0.19 0.83 19.49 0.11 0.001***Provision of literacy materials -0.18 0.61 0.08 0.57 6.86 0.04 0.010*Parent storybook reading interest -0.37 1.02 0.17 0.66 15.12 0.09 0.001***Parent literacy mediation -0.36 0.69 0.16 0.63 21.13 0.12 0.001***Parent play activities 0.03 0.77 -0.01 0.85 0.08 0.00 0.777Parent book reading -0.06 0.70 0.03 0.69 0.59 0.00 0.443Parent email use -0.36 1.16 0.16 0.77 10.75 0.07 0.001***Parent magazine reading -0.17 0.95 0.07 0.80 2.66 0.02 0.105Parent newspaper reading -0.14 0.85 0.07 0.81 1.89 0.01 0.172

*P � 0.05 (two-tailed), **P � 0.01 (two-tailed), *** P � 0.001 (two-tailed).CA, chronological age; HLE, home literacy environment; ID, intellectual disability.

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expectations (73%) or lower expectations abouttheir child’s writing level at the end of elementaryschool; i.e., they expected their child to be unableto write (2%), to be able to write letters (6%) orwords (8%). Only 2% of the parents of childrenwith ID expected their child to be able to writesimple texts and 8% of the parents expected theirchild to be able to write longer texts. Most of theparents of children without disabilities had highexpectations for their child’s writing level; i.e., theyexpected their child to be able to write longer texts(80%) or simple texts (10%). Only 3% of theseparents had low expectations for the writing levelof their child and 7% of the parents had noexpectations.

Comparison with children of the same mental age

The second research question concerned the com-parison of the children with ID and the MA group.The results can be found in Table 3. Again, signifi-cant differences in the HLE between these twogroups were found, Wilks’ Lambda = 0.313,F15,57 = 8.33, P < 0.001 and hp

2 = 0.69. The differ-ences between the ID and MA groups were similaras those between the ID and CA groups; however,

no differences were found in comparing the IDgroup with the MA group for the following factors:child’s activities with literacy materials, word orien-tation activities, provision of literacy materials andparent literacy mediation.

The parents of children with ID showed the sameexpectation pattern as described in the previousparagraph, with similar results for expectations fortheir child’s reading level [c2 (4, n = 73) = 50.20,P < 0.001 and eta = 0.812] and writing level [c2 (4,n = 73) = 55.47, P < 0.001 and eta = 0.832] at theend of elementary school.

Relationships between child variables and thehome literacy environment

The third research question was concerned with therelationships between aspects of the HLE and chil-dren’s non-verbal intelligence, speech intelligibility,language and early literacy skills within the group ofchildren with ID. In Table 4 the mean scores andSDs of the children with ID on the standardisedtasks can be found.

Table 5 shows the correlations between the childvariables and aspects of the HLE. As can be seen,children who were engaged in more activities with

Table 3 Descriptive statistics of the HLE factors for the group of children with ID (n = 37) and the MA comparison group (n = 36)

HLE factors

ID MA

F hp2 PM SD M SD

Child’s writing activities -0.31 0.87 0.32 0.57 13.49 0.16 0.001***Child’s storybook reading interest -0.42 1.01 0.43 0.48 20.92 0.23 0.001***Child’s activities with literacy materials 0.02 0.66 -0.03 0.60 0.11 0.00 0.740Story orientation activities -0.30 0.56 0.31 0.63 19.35 0.21 0.001***Book orientation activities 0.31 0.84 -0.32 0.52 14.58 0.17 0.001***Picture orientation activities -0.21 0.99 0.21 0.67 4.49 0.06 0.038*Word orientation activities 0.12 0.98 -0.12 0.64 1.57 0.02 0.215Provision of literacy materials 0.03 0.69 -0.03 0.44 0.15 0.00 0.697Parent storybook reading interest -0.28 0.93 0.29 0.59 9.89 0.12 0.002***Parent literacy mediation -0.06 0.74 0.06 0.56 0.58 0.01 0.447Parent play activities -0.10 0.82 0.10 0.82 1.07 0.02 0.306Parent book reading -0.08 0.74 0.08 0.68 0.90 0.01 0.346Parent email use -0.39 1.04 0.40 0.61 15.37 0.18 0.001***Parent magazine reading -0.15 0.95 0.15 0.77 2.10 0.03 0.152Parent newspaper reading -0.27 0.85 0.28 0.79 8.10 0.10 0.006**

*P � 0.05 (two-tailed), **P � 0.01 (two-tailed), *** P � 0.001 (two-tailed).HLE, home literacy environment; ID, intellectual disability; MA, mental age.

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literacy materials had a higher MA, productivesyntax age, productive vocabulary age and higherbook orientation skills (all Ps < 0.05). Furthermore,the more involved children were during storybookreading, the higher their MA, receptive languageage, productive syntax age, productive vocabularyage, book orientation and rapid naming of pictures(all Ps < 0.05).

The more literacy materials parents provided fortheir children, the higher the productive syntax ageand level of book orientation of the children (allPs < 0.05). Parent play activities were also positivelyrelated to children’s speech intelligibility (P < 0.05).

Conclusions and discussion

Conclusions

In the present study, the HLE of children with IDwas compared with that of children without dis-abilities to find out to what extent there were differ-ences, and if so, of what nature these differenceswere. First of all, the HLE of children with ID dif-fered in many aspects from that of children withoutdisabilities of the same CA. Differences were notonly found in activities the children engaged inthemselves, but also in the amount of literacy mate-rials parents provided for their children and in lit-eracy activities parents engaged in with theirchildren. Children with ID had fewer experienceswith reading, writing and drawing materials, andshowed less interest in storybook reading activitiesthan their peers without disabilities. During story-book reading sessions, they were less involved in

story, picture and word orientation activities thanchildren without disabilities of the same CA, forexample, pointing at pictures, letters or words,asking questions about the story or give commentson the story. These results are in line with previousresearch (Marvin & Mirenda 1993; Marvin &Wright 1997; Peeters et al. in press).

Furthermore, a comparison was made betweenthe HLE of children with ID and children withoutdisabilities of the same MA. Differences with chil-dren of the same MA mainly concerned the activi-ties the children engage in themselves (e.g. child’swriting activities, child’s storybook reading interestand story orientation activities) and not parent-initiated activities (e.g. parent literacy mediationand provision of literacy materials). These resultsindicate that parents adapt their level of communi-cation to the developmental age of their child (cf.Kaiser et al. 2001). It seems that the differencesfound between children with ID and the MA groupwere largely caused by the child variables (e.g. cog-nitive and speech disabilities) of the children withID. This means that, although parents adapted theirHLE practices to the developmental level of theirchild, the children with ID showed less literacyactivities.

A large part of the children with ID was non-speaking (19 children), and this could have influ-enced the results, as children who do not speak maynot give much feedback to parents during story-book reading, resulting in less interactive storybookreading sessions. However, the results remained thesame in additional analyses without the non-speaking children, suggesting that the cognitive dis-abilities and not the speaking disabilities of thechildren were the main cause of the differencesfound in HLE.

Another difference between the groups concernsthe expectations parents have of their child’s lit-eracy development. Most parents of children withID did not know what to expect of their child’sfuture reading and writing levels, and if they hadexpectations, these were generally lower. In con-trast, parents of children without disabilities almostall had high expectations for their child’s readingand writing levels at the end of elementary school(cf. Marvin & Mirenda 1993; Marvin 1994; Peeterset al. in press). The expectations parents have aboutthe literacy development of their children influence

Table 4 Descriptive statistics of the standardised tasks for the groupof children with intellectual disabilities (n = 48)

Standardised task M SD

Mental age (months) 34.8 8.2Receptive language age (months) 33.3 9.0Productive syntax age (months) 30.1 10.5Productive vocabulary age (months) 32.4 10.5Auditory discrimination 11.8 5.2Speech intelligibility 1.2 2.5Book orientation 1.6 2.7Rapid naming pictures 13.0 12.5

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this development (Lee & Groninger 1994), and thisalso goes for children with ID (Koppenhaver et al.1991; Al Otaiba et al. 2009). It is therefore impor-tant for future research to find out why parents ofchildren with ID do not know what to expect oftheir child’s literacy development, and to focus onhow to guide parents in stimulating their child’sliteracy development in the best possible way.

Another interesting finding of this study is that,although the children with ID scored lower on allaspects of the HLE compared with the CA and theMA groups, they scored higher on one factor: bookorientation activities. A higher score on this factormeans that children were more active during story-book reading than children without disabilities onthe following behaviours: holding the book, indicat-ing the tempo and turning the pages. It seems thatchildren with ID were dominating the book readingsessions by showing these behaviours. This is prob-ably caused by their lack of interest for books andreading, as was also seen in the analyses of thequestionnaires (i.e. child’s storybook reading inter-est). It could, however, also be the case that asparents have less clear expectations of their child’sliteracy abilities, they allow their child to set the

pace of storybook reading more and thus to domi-nate the book reading session.

The third research question focused on relation-ships between child characteristics and HLE withinthe group of children with ID. It was found that thebetter the child’s intelligence and receptive and pro-ductive language skills were, the more active thechild was with literacy materials and the more storyand word orientation activities the child showedduring storybook reading sessions. Children’s levelof book orientation (e.g. what a child knows aboutbooks) was related to the amount of literacy materi-als in the home and the child’s activities with thesematerials. We can thus conclude that, as for childrenwithout disabilities, the HLE also makes an impor-tant contribution to the language and early literacydevelopment of children with ID.

Limitations and suggestions for future research

The results of the present study should be inter-preted in light of some limitations. First, to measurethe HLE of the children, parent questionnaires wereused. Parents may be tended to give socially accept-able responses and thus withheld any negative

Table 5 Pearson’s correlations between HLE factors and child variables for children with intellectual disabilities (n = 48)

HLE factors MA RLA PSA PVA AUD† ART† Book† RAN†

Child’s writing activities 0.22 0.20 0.08 0.14 0.03 0.24 0.14 0.22Child’s storybook reading interest 0.04 0.03 0.18 -0.01 0.05 -0.12 0.27 0.10Child’s activities with literacy materials 0.38** 0.25 0.31* 0.34* 0.18 0.04 0.38** 0.22Story orientation activities 0.65*** 0.60*** 0.43** 0.52*** 0.29 -0.12 0.25 0.29*Book orientation activities 0.11 0.06 -0.29 -0.14 -0.16 -0.28 -0.19 -0.22Picture orientation activities 0.21 0.20 -0.05 0.18 0.09 0.09 0.06 0.15Word orientation activities 0.44** 0.40** 0.13 0.33* 0.24 -0.00 0.38** 0.18Provision of literacy materials 0.16 0.08 0.35* 0.13 0.04 -0.12 0.44** 0.11Parent storybook reading interest -0.00 -0.01 0.13 -0.00 0.03 -0.17 0.16 0.07Parent literacy mediation 0.19 0.19 -0.00 0.25 0.16 -0.10 0.14 0.07Parent play activities 0.08 0.01 0.25 0.01 0.25 0.34* 0.01 0.23Parent book reading -0.12 -0.09 0.24 0.02 -0.12 -0.21 0.26 0.02Parent email use -0.03 -0.08 -0.14 -0.10 -0.48*** 0.21 -0.12 -0.22Parent magazine reading 0.20 0.10 0.23 0.11 -0.04 0.04 0.16 0.16Parent newspaper reading -0.08 0.02 -0.20 0.09 0.04 -0.24 -0.05 -0.09

* P � 0.05 (two-tailed), ** P � 0.01 (two-tailed), *** P � 0.001 (two-tailed).† Partial correlations with chronological age as covariable.HLE, home literacy environment; MA, mental age; RLA, receptive language age; PSA, productive syntax age; PVA, productive vocabularyage; AUD, auditory discrimination; ART, speech intelligibility; Book, book orientation; RAN, rapid naming pictures.

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beliefs they had about literacy. In future research,questionnaires should therefore be supported byobservational data of the HLE of children. In thisway the literacy practices in the home can beobserved, which will give more information aboutthe HLE of the children and the interactions thatoccur between parents and their children.

Furthermore, some parents of children with IDindicated that they did not read to their child andtherefore did not fill in the questionnaire. It thusseems that there are parents of children with IDthat did not return the questionnaire for thisreason. This could explain the lower response rateof the parents of children with ID (64% in contrastto 85% and 76% for the control groups). It wouldalso mean that only those parents that actually didsome literacy activities with their childrenresponded to the questionnaire, suggesting that thedifferences between the groups may be even larger.

Another limitation is the lack of longitudinal dataabout the children’s language and literacy develop-ment. The direction of the relationships foundbetween HLE factors and children’s language andliteracy skills cannot be determined without longi-tudinal data. This means that it is unknown whichaspects of the HLE may predict later language andliteracy development of the children. Futureresearch should take this into account and includelongitudinal data of children’s language and literacydevelopment. This can shed more light on whichaspects of the HLE may predict later language andliteracy skills of the children.

Clinical implications

Some important clinical implications can be derivedfrom the present study. First of all, it is importantthat parents are informed about their child’s abili-ties to become literate and which role parents playin this development, as the results showed thatmany parents of children with ID did not knowwhat to expect for their child’s literacy develop-ment. Furthermore, literacy development shouldalso become a more important goal for parents, asit is most often just not seen as a priority for thosechildren. Becoming literate, however, may especiallyserve those children that have a hard time commu-nicating effectively with others (e.g. children withspeech language impairments). Communicating

effectively is almost always seen as a top prioritygoal by parents of children with IDs, where becom-ing literate is placed at a consistently lower level(Marvin & Mirenda 1993; Trenholm & Mirenda2006).

An important way to stimulate children’s literacydevelopment is making use of interactive storybookreading. The quality of storybook reading interac-tions has been shown to affect language and earlyliteracy development of children with ID (Hargrave& Sénéchal 2000; Peeters et al. 2009). Instead ofjust reading a book cover to cover to their child,parents should be taught to make use of a moreinteractive way of reading in which they make surethat their child takes a more active role in the inter-action. In a study of Katims (1994), children withID were repeatedly read the same stories, whichmade them familiar with the text. This familiaritymade it possible for the children to re-enact thestories and relate the stories to their daily life. Fur-thermore, scaffolding during storybook readingleads to vocabulary development and an increase ofcommunicative turns in children with languageimpairments (Hargrave & Sénéchal 2000; Croweet al. 2004). Enhancing children’s activity duringstorybook reading can also be done by introducingor using Augmentative and Alternative Communica-tion (e.g. objects, pictograms and signs) during sto-rybook reading, which will give non-verbal childrenthe possibility to react on the story.

Literacy instruction in classrooms for childrenwith ID should be concrete and meaningful(Katims 2000). Many teaching activities, however,focus on teaching-isolated subskills to children.Children with ID have difficulty with learning theseabstract skills and with the transfer of this isolatedknowledge to reading books for information andpleasure. However, research has demonstrated thatwhen literacy teaching is done in a meaningfulcontext in which the interest of the child is fol-lowed, children with ID are able to become literatein a conventional way (Koppenhaver et al. 1991;Koppenhaver & Erickson 2003).

To conclude, there are differences between theHLE of children with ID and the HLE of childrenwithout disabilities. These differences are largestwhen children are compared with children of thesame CA. When children of the same MA are com-pared, differences in activities children engage in

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themselves still remain, indicating that the HLE islargely influenced by the cognitive disabilities of thechildren. However, parents also adapt their level tothe developmental level of their child, which maynot always be the most stimulating for the children.

Acknowledgements

This study was funded by the European Union,Interreg 4-BMG-V-1=31, Fund Nuts-Ohra (Amster-dam, the Netherlands) and Viataal (St.Michielsges-tel, the Netherlands). Special appreciation isexpressed to the children and parents who partici-pated, and the clinical experts of the participatingday-care centres and schools.

Notes

1 The children with ID and the MA comparisonchildren also took part in a larger longitudinal studyinvestigating the language development of childrenwith ID.2 The results of this c2 should be interpreted withcaution, as more than 20% of the cells haveexpected cell frequencies less than 5 and/or theminimum expected cell frequency is less than 1.

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Accepted 25 September 2009

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Appendix 1

Results of the factor analyses of the four parent questionnaires1 Factor Analysis of Child’s Literacy Interest

Items Factor 1 Factor 2 Factor 3

Child’s literacy interest Child’s writing activities Child’s storybookreading interest

Child’s activitieswith literacy materials

Frequency of using child magazines -0.04 -0.02 0.59Frequency of using comic books -0.13 -0.08 0.45Frequency of using dictionaries and/or encyclopaedias -0.08 0.05 0.37Frequency of using a computer or typewriter 0.21 -0.09 0.51Frequency of using play-do books -0.01 0.09 0.45Frequency of using writing materials 0.99 -0.06 -0.13Frequency of using drawing materials 0.84 -0.00 -0.10Child’s interest in drawing, painting or colouring 0.60 0.06 0.09Child’s interest in writing or reading letters or words 0.40 0.15 0.29Frequency of using child books 0.03 0.63 0.03Child’s interest in storybook reading 0.00 0.84 0.04Frequency of asking to be read to -0.02 0.95 -0.09

Reliability coefficient (Cronbach’s a) 0.77 0.73 0.63Eigenvalue 3.85 1.78 1.43Per cent explained variance 29.61 13.66 10.99

Intercorrelations1 –2 0.42 –3 0.30 0.41 –

2 Factor Analysis of Child’s Activities during Storybook Reading

Factor 1 Factor 2 Factor 3 Factor 4ItemsChild’s activities during storybook reading

Story orientationactivities

Book orientationactivities

Picture orientationactivities

Word orientationactivities

Holding the book 0.10 0.55 -0.05 0.08Indicating the tempo -0.06 0.53 -0.12 0.05Turning the pages -0.02 0.79 0.12 -0.09Pointing at pictures -0.08 -0.02 0.98 -0.01Naming pictures 0.21 -0.04 0.40 0.16Pointing at letters or words -0.07 0.07 0.02 0.87Reading aloud letters or words 0.18 -0.07 0.03 0.40Asking questions about the story 0.62 -0.16 0.08 -0.11Retelling the story in own words or by using AAC 0.60 0.13 0.03 0.02Guessing how the story will end 0.64 0.03 -0.07 0.04Give comments on the story 0.60 -0.03 -0.09 0.07Make up own story with the pictures 0.70 0.10 0.02 -0.09Relating the story to experiences in daily life 0.45 -0.06 -0.01 0.07

Reliability coefficient (Cronbach’s a) 0.71 0.73 0.68 0.61Eigenvalue 3.40 1.85 1.30 1.06Percent explained variance 26.17 14.20 10.01 8.17

Intercorrelations1 –2 -0.01 –3 0.27 0.16 –4 0.45 0.04 0.26 –

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3 Factor Analysis of Materials and Parental Activities for Child Literacy Development

ItemsMaterials and parental activities for childliteracy development

Factor 1Provision ofliteracymaterials

Factor 2Parentstorybookreadinginterest

Factor 3Parentliteracymediation

Factor 4Parentplayactivities

Number of own book of the child 0.52 0.26 -0.02 -0.01Number of child magazines available 0.40 -0.13 0.09 0.04Number of child books 0.74 0.26 -0.23 -0.02Number of comic books 0.40 -0.06 -0.10 0.03Number of dictionaries or encyclopaedias for children 0.57 0.03 -0.14 -0.02Number of tape-recorded stories 0.45 -0.20 0.19 -0.07Number of songbooks 0.44 -0.04 0.07 0.01Number of play-do books 0.55 -0.19 0.25 0.21Frequency of reading to the child -0.08 0.88 0.12 -0.10Enjoying storybook reading to the child -0.07 0.50 0.08 0.15Frequency of picture-book reading together with the child 0.03 0.74 0.04 0.05Frequency of involving the child in own reading 0.03 -0.02 0.41 0.13Frequency of involving the child in own writing -0.09 0.07 0.62 0.11Frequency of playing rhyme games with the child 0.20 0.05 0.39 -0.10Frequency of reading names or letters with the child 0.08 0.03 0.65 -0.04Frequency of reading recipes or shopping lists with the child -0.11 0.03 0.70 0.07Frequency of playing with the child -0.10 0.23 -0.03 0.64Frequency of playing outside the home with the child 0.06 -0.04 0.02 0.55

Reliability coefficient (Cronbach’s a) 0.75 0.75 0.71 0.23Eigenvalue 4.44 2.18 1.86 1.28Percent explained variance 20.20 9.89 8.46 5.82

Intercorrelations1 –2 0.47 –3 0.29 0.28 –4 -0.03 0.29 0.23 –

4 Factor Analysis of Parents’ own Literacy Materials and Activities

ItemsFactor 1 Factor 2 Factor 3 Factor 4

Parents’ own literacy materials and activitiesParent bookreading

Parentemail use

Parent magazinereading

Parent newspaperreading

Number of reading books 0.64 0.06 0.12 0.05Number of study books 0.80 0.01 -0.10 0.07Number of dictionaries and encyclopaedias 0.65 -0.12 0.11 0.03Frequency of reading informative books 0.45 -0.01 0.05 -0.03Frequency of writing a letter or story 0.38 0.20 -0.16 -0.10Number of magazines 0.19 -0.10 0.63 -0.17Frequency of reading magazines -0.12 0.12 0.75 0.11Number of newspapers 0.10 -0.09 -0.04 0.48Frequency of reading the newspaper 0.02 0.06 -0.02 0.77Frequency of reading email -0.02 0.79 -0.01 -0.04Frequency of writing email 0.04 0.90 0.05 0.00

Reliability coefficient (Cronbach’s a) 0.76 0.88 0.67 0.58Eigenvalue 3.01 1.80 1.36 1.23Percent explained variance 25.08 15.03 11.33 10.23

Intercorrelations1 –2 0.15 –3 0.34 0.19 –4 0.34 0.03 0.26 –

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