Do not show videos to infants. The current consensus in the scientific community is that for small children, the effects of screen time are overwhelmingly negative. There are few, if any, positive effects.
For children younger than 18 months, avoid use of screen media other than video-chatting.
American Academy of Pediatrics Announces New Recommendations for Children’s Media Use: https://services.aap.org/en/news-room/news-releases/aap/2016/aap-announces-new-recommendations-for-media-use/
The developing brain and screen time
Excessive media use in children has been associated with a number of undesirable health outcomes, such as reduced sleep (Hale & Guan, 2015), increased obesity, and language and social emotional delays (AAP, 2016). However, the effects of media usage on brain development and health outcomes are not fully understood at this time. ...
For young children, the best way to teach higher-order cognitive skills (including attentional and emotional control) is through parent-child interactions, unstructured and social play (AAP, 2016). Letting toddlers use or view media on their own should be avoided. In older children, more research is needed to understand how specific periods of brain development relate to media use.
Media use in childhood: Evidence-based recommendations for caregivers: https://www.apa.org/pi/families/resources/newsletter/2019/05/media-use-childhood
The fact is, the amount of TV a child should watch before the age of 2 is zero.
TV can lead to hostility, trouble focusing
For decades we have known of the connection between hostile peer interactions and the amount of kids exposure to television. The linkage used to be controversial (maybe aggressive people watch more TV than others?), but we now see that it’s an issue of our deferred-imitation abilities coupled with a loss of impulse control. [...]
Another example comes from a study that looked at bullying. For each hour of TV watched daily by children under age 4, the risk increased 9 percent that they would engage in bullying behavior by the time they started school. This is poor emotional regulation at work. Even taking into account chicken-or-egg uncertainties, the American Association of Pediatrics estimates that 10 percent to 20 percent of real-life violence can be attributed to exposure to media violence.
TV also poisons attentions spans and the ability to focus, a classic hallmark of executive function. For each additional hour of TV watched by a child under the age of 3, the likelihood of an attentional problem by age 7 increased by about 10 percent. So, a preschooler who watches three hours of TV per day is 30 percent more likely to have attentional problems than a child who watches no TV.
Just having the TV on while no one is watching — secondhand exposure — seemed to do damage, too, possibly because of distraction. In test laboratories, flashing images and a booming sound track continually diverted children from any activity in which they were otherwise engaged, including that marvelous brain-boosting imaginative play we discussed. The effects were so toxic for kids in diapers that the American Association of Pediatrics issued a recommendation that still stands today:
"Pediatricians should urge parents to avoid television viewing for children under the age of 2 years. Although certain television programs may be promoted to this age group, research on early brain development shows that babies and toddlers have a critical need for direct interactions with parents and other significant caregivers (e.g., child care providers) for healthy brain growth and the development of appropriate social, emotional, and cognitive skills."
Current research projects are addressing the potential effect of TV on grades, and preliminary work suggests that it affects both reading scores and language acquisition. But after age 2, the worst effects on kids brains may come because television coaxes kids away from exercise, a subject we will examine when we get to video games.
TV aimed at babies not so brainy
What about all those store shelves lined with educational videos and DVDs? They certainly claim to boost cognitive performance in preschool populations. Such boasts inspired a group of researchers at the University of Washington to do their own studies. [...]
The products didn’t work at all. They had no positive effect on the vocabularies of the target audience, infants 17 to 24 months. Some did actual harm. For every hour per day the children spent watching certain baby DVDs and videos, the infants understood an average of six to eight fewer words than infants who did not watch them.
Disney demanded a retraction, citing deficiencies in the studies. After consultations with the original researchers, the university held its ground and issued a press release saying so. After this initial flurry of activity, there was silence. Then, two years later, in October 2009, Disney made what amounted to a product recall, offering refunds to anyone who had purchased Baby Einstein materials. Responsibly, the company has dropped the word “educational” from the packaging.
Medina, J. (2010). Brain rules for baby: How to raise a smart and happy child from zero to five. Seattle: Pear Press. https://www.amazon.com/Brain-Rules-Baby-Raise-Smart/dp/0983263302/