From a QZ post:
Science tells us that, when it comes to children’s cognitive development, reading on screens is just as effective as reading on paper. But the parent-child relationship benefits more from story time with a paper book than with a tablet, because the interaction is warmer and friendlier.
A study by University of Sussex psychologists in the UK, published in Frontiers in Psychology compared changes in cognitive, affective, and postural aspects of interaction during shared reading on screen and on paper. The researchers, Nicola Yull and Alex Martin, were interested in how technology impacts shared activities, which is known to influence children’s linguistic and literary abilities later in life.
Video observations of shared reading sessions of 24 sets of British mothers and their kids, ages seven to nine—sometimes with the child reading and at others with the mother reading—revealed that physical book sessions were more lively and loving than shared tablet reading. The researchers also tested for cognitive differences, such as retention, but found none.