The basic finding is that children’s brains are activated differently in emerging readers depending on how the content was fed to them. Audio-only had little brain activation, meaning just playing an audiobook or reading without letting the child see or hold the book is not highly effective. The opposite was true of full-on voice and animation, which left the child with very little to do in terms of activating their brains to understand the content. The middle ground, reading to a child while showing them static illustrations, required the most interaction in the brain and developed the most connection with the content.
There has long been a case for the “calmness” associated with e-ink e-readers for children’s content.