The analysis included 54 studies conducted between 1989 and 2017. These studies included 316 effect sizes and 5,569 participants. Nine of the studies reported follow-up effects. Children in the studies were typically age 7 years or younger.
Their findings suggest that, while there is an effect of shared reading on language development, the effect size is smaller than suggested in previous meta-analyses (+0.23). They also found that the effect size is moderated by the type of control groups, and when compared to active control groups, is closer to zero (+0.04). In addition, the meta-analysis indicates only modest differences between types of language outcomes, no effect for socioeconomic background, and a near-zero effect at follow-up.
However, given the low dosage of many of the studies included in the meta-analysis, the authors caution against the conclusion that shared reading interventions have no real effect on children's language development.