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In line with the early reviews by Scarborough and Dobrich (1994) and Bus et al. (1995), several subsequent studies have shown that the frequency of storybook exposure in the early years reliably predicts a number of child outcomes. However, children’s age when parents begin reading storybooks with them has been mooted as a stronger correlate of oral language than frequency counts (e.g. DeBaryshe, 1993), suggesting that the effects of storybook exposure may be cumulative over time. Payne et al. (1994) used a composite measure derived from nine questionnaire items (frequency and duration of shared reading, child’s age at the onset of shared reading, number of books in the home, frequency of library visits, frequency of children’s requests to be read to, frequency of children’s independent reading, frequency of caregiver reading and caregivers’ enjoyment of reading) to tap HLE. Their analysis showed that aggregating predictor and outcome scores yielded stronger inter- correlations. However, it is possible that pooling across receptive and expressive language domains may mask differential effects of HLE on children’s ability to understand, as opposed to produce, spoken language. Other studies have indicated that the effects of storybook exposure may be most strongly related to children’s language comprehension (DeBaryshe, 1993).

22 Griffin and Morrison (1997) developed a Home Literacy Environment Questionnaire which assessed the frequency of shared reading and of library visits, the presence of literacy resources in the home, parents’ own literate behaviours and the frequency of activities which might be expected to displace literacy activities, such as hours of television viewing. The authors went on to report that in a sample of 295 American kindergarten children, the HLE measure predicted unique variance in children’s concurrent receptive vocabulary, general knowledge and reading recognition. The predictive power of pre-school HLE in general knowledge and reading recognition, but not receptive vocabulary, was maintained when the children were tested in Grade 2.

However, self-report measures are vulnerable to a number of response biases, and when reporting on an activity so universally approved as reading storybooks to children, it might be expected that parental report, as tapped by HLE questionnaires, would be susceptible to the effects of social desirability. To circumvent this confound, Stanovich and West (1989) developed a method designed to tap children’s exposure to storybooks in the home more objectively: Title and Author Recognition

Checklists. Parents (or older children) are presented with a list of titles of well-

known storybooks targeted at the relevant age-group, which includes a number of invented foils, and simply asked to tick the titles which they recognise as authentic. A similar list of the names of authors of popular children’s storybooks can be used as an alternative, or in addition, to the Title Recognition Checklist. Stanovich and West (1989) found their Author Recognition Test to be a robust and independent predictor or orthographic processing in a sample of American undergraduates. Stainthorp (1997) found scores on an adapted Author Recognition Checklist for Children (CART-UK) to be well correlated with British children’s reading performance.

23 These checklist tools are clearly an indirect way of measuring storybook exposure; their rationale being that parents who recognise more titles and authors of children’s literature are more likely to engage in frequent shared storybook reading with their children. However, data from checklists typically show convergent validity, correlating with parent reports of storybook exposure, and predictive validity, correlating with children’s later oral language skills. For instance, Frijters, Barron and Brunello (2000) found that a composite HLE measure taken from five parental-report items correlated with children’s receptive vocabulary (r=.24) in a sample of Canadian 5- and 6-year olds, but that the association was stronger when a Parental Title Recognition Checklist was added as an indicator of storybook exposure (r=.39). A direct effect of HLE on oral language was highlighted by a multiple regression analysis, where shared reading (parental report and checklist) and children’s interest in literacy accounted for 21% of the variance in children’s receptive vocabulary.

Unusually, Evans, Shaw and Bell (2000) found that their parental-report measure of the frequency of shared reading did not correlate with a Children’s Title Recognition Checklist. However, given that the checklists were posted to parents rather than administered face-to-face by researchers, the validity of this measure may have been compromised. Evans et al. (2000) went on to show that, in their sample of 67 Canadian children, after accounting for children’s age, cognitive ability and parental education level, storybook exposure as reflected by the checklist scores did not account for unique variance in any language or literacy outcomes. This pattern of results is discrepant with the broader literature, and perhaps reflects the use of a relatively small, mixed SES sample. Parental education level was well correlated with storybook exposure in this study, and these two variables may largely have

24 accounted for the same variance in child outcomes. However, as discussed previously, parental education is a purely descriptive environmental predictor of language and reading development, whereas storybook exposure constitutes a plausible mechanism by which differences in parental education level operate on development.