Richards, J.E. (2018). Media effects on young children: An attention development perspective. Media Exposure and Child Development, NIH, January 2018.(pdf )
Conclusions: From age 3 mo to about 12 mo, minor effects of video program on extended fixations. Neural development of several “core attention systems” affecting fixation and attention. Development of brain systems for attending to the environment and likely social brain development. Synchronized audio-visual stimuli elicit most attention 18 and 24 months--Comprehensible and age-appropriate stimuli elicit extended fixations and hear rate indicating attention engagement.