By Dan Willingham
Melby-Lervåg et al. included 235 studies in their analysis and concluded that existing research suggests that all three—rime awareness, phoneme awareness, and size of verbal short-term memory—predict word reading but the largest effect is observed with phonemic awareness. (In fact, the predictive value of verbal short-term memory is quite small.)
The second important conclusion from this review concerns causality. All of these studies in the meta-analysis are correlational. Hence, one interpretation is that phonemic awareness is related to word reading skills because phonemic awareness is necessary for that skill. However, an equally viable interpretation is that reading changes phonemic awareness, so the association is observed because more skilled readers have undergone greater change.