Found effects

The WWC found Dialogic Reading to have positive effects for oral language and no discernible effects for phonological processing

Improvement index

The WWC computes an improvement index for each individual finding. In addition, within each outcome domain, the WWC computes an average improvement index for each study as well as an average improvement index across studies (see Technical Details of WWC-Conducted Computations). The improvement index represents the difference between the percentile rank of the average student in the intervention condition and the percentile rank of the average student in the comparison condition. Unlike the rating of effectiveness, the improvement index is entirely based on the size of the effect, regardless of the statistical significance of the effect, the study design, or the analysis. The improvement index can take on values between -50 and +50, with positive numbers denoting favorable results.

The average improvement index for oral language is +19 percentile points across the five studies, with a range of -6 to +48 percentile points across findings. The average improvement index for phonological processing is +9 percentile points for the one study, with a range of -7 to +40 percentile points across findings.

Findings for Dialogic Reading plus Sound Foundations

The study described below does not contribute to the overall rating of effectiveness because the intervention included a combination of Dialogic Reading and Sound Foundations, which does not allow the effects of Dialogic Reading alone to be determined. However, the WWC believes that the findings from this combined intervention may provide useful information to practitioners who are making a determination about the merits of combining Dialogic Reading with a supplemental phonological awareness curriculum (Sound Foundations). The WWC reports the individual study findings here and in Appendix A4.

Whitehurst, Epstein, et al. (1994) included 167 at-risk lowincome four-year-old children from four Head Start centers in Suffolk County, New York. Whitehurst, Epstein, et al. compared oral language, print knowledge, phonological processing, and early reading/writing outcomes for children participating in Dialogic Reading combined with an adapted Sound Foundations curriculum to outcomes for children in a no-treatment comparison group participating in their regular Head Start services.

Oral language. Whitehurst, Epstein, et al. (1994) found no statistically significant difference between the intervention group and the comparison group on oral language as measured by the Language factor.¹³ Zevenbergen, Whitehurst, and Zevenbergen (2003), a second report on the same study, reported findings on four additional oral language measures from the same study, none of which were statistically significant as calculated by the WWC. The average effect across the five measures was neither statistically significant nor large enough to be considered substantively important, according to WWC criteria. The average improvement index for oral language is +6 percentile points with a range of -12 to +19 percentile points across findings.

Print knowledge. Whitehurst, Epstein, et al. (1994) reported a statistically significant difference favoring the intervention group on the Print concepts factor. ¹³ The statistical significance of this effect was confirmed by the WWC. The improvement index for print knowledge is +24 percentile points for the one print knowledge outcome in this study.

Phonological processing. Whitehurst, Epstein, et al. (1994) reported neither statistically significant nor substantively important effects on the Linguistic awareness factor. ¹³ The improvement index for phonological processing is +1 percentile point for the one phonological processing outcome in this study.

Early reading/writing. Whitehurst, Epstein, et al. (1994) reported a statistically significant difference favoring the intervention group on the Writing factor. ¹³ The statistical significance of this effect was confirmed by the WWC. The improvement index for early reading/writing is +20 percentile points for the one early reading/writing outcome in this study.

Summary

The WWC reviewed eight studies on Dialogic Reading. Four of the studies met WWC standards and one study met WWC standards with reservations. One additional study that met WWC standards is described in this report but is not included in the overall rating of effectiveness. The remaining two studies did not meet evidence screens. Based on the five studies included in the overall rating of effectiveness, the WWC found positive effects for oral language and no discernible effects for phonological processing. Findings from one study suggest that level of implementation of Dialogic Reading influences the impact of the practice on children's oral language skills. Based on the study that included a Dialogic Reading plus Sound Foundations intervention, the WWC found no discernible effects on oral language, potentially positive effects on print knowledge, no discernible effects on phonological processing, and potentially positive effects on early reading/writing. The evidence presented in this report may change as new research emerges.

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