THE NEGATIVE EFFECTS OF MEDIA
When this website was created in 2009, there was very little about this subject online, and most of the research still referred to television only. This still remains the most popular page on this site. Now when one does a search, one discovers a huge amount of information and studies done about the negative effects of screens on children of different ages. Here is a very small compilation.
This theme is very large, and could make up volumes in itself. The American Academy of Pediatrics recommends that children under two be kept away from any screens because of the negative effects it can have on development at this crucial stage.  The negative effects on development and health seem to continue for later years as well. , Here are some thoughts and facts gathered as an introduction to further reading.
“On reflection, watching television is a very poor investment
in your child’s future.” Dr. Aric Sigman 
What research and studies say
A study that monitored children between the ages of two and four compared their time listening to television and their language development, and found that for each hour of television heard, their age-appropriate language skills decreased. Another study showed that children with televisions in their rooms clearly showed lower school performance levels.
There is a huge amount of research that shows the negative effects of television, computers and video games on young children in many areas of development., They deprive the child of sensory experiences in seeing, hearing, and touch they have while doing active things in the real world. Developing co-ordination, sense of balance, general motor and fine motor skills, and physical fitness as well as social skills developed in play with others, are all important for short and long-term physical and mental health. There is a clear correlation between exposing children to TV between the ages of one and three and the development of attention problems (ADHD) later on. Watching television in childhood and adolescence is associated with being overweight, early puberty, poor fitness levels, smoking, higher cholesterol in adulthood. ,, Studies also show that the viewing patterns children have as toddlers will influence their viewing habits for the rest of their lives.
Studies with one, two and three year olds have revealed marked negative effects of background television on their ability to play in a focused manner, though they were not watching it., Though studies have yet to be done, it would be of little surprise if radio noise had the same effect. Many studies show that children exposed to higher levels of noise have higher blood pressure, a higher heart rate, as well as lower cognitive and language skills., 
Up to about ten months, babies will usually not respond to what is on a screen, but they are very sensitive to the emotions of others around and will pick up, even unnoticed, how others are reacting to what they are watching. Any strong emotions are stressful to a baby, and are not conducive to growing and learning, as well as having a potential effect on how their bodies develop. As for being exposed to constant background noise of TV or radio or music, studies show it having a negative impact on the baby's ability to recognize language, sounds of nature and human sounds.
Weakening the social sense
There are also more subtle consequences of children being exposed to media and recordings. When we meet someone in person, and interact with him or her, we get a sense of who they are. We find out so much about them that cannot be discovered over the phone or even in video recordings of them. As we grow up, we develop a sense for people, we learn to observe subtle signs and traits that help us to understand people and recognize subtleties and changes in them. It is through this sense of people that we are able to have empathy towards them and discernment, and how we are able to adapt our interactions with each person and situation accordingly. These are crucial elements for all of social life and for any healthy interpersonal relationships.
Recorded voices (speaking or singing) TV, cartoons, video games, are disembodied impressions of human beings (or human-like in the case of animation) that give us only part of the information about who is there. A young child receiving these is still unable to judge something as being a recording; a child receives what is there as a whole thing. He gradually perceives that the voices, the figures in the TV or computer don't respond to the present situation: The music or the recorded voice persists or stays at the same volume, not adapting to what is happening in the immediate surroundings of the child. On a more subtle level, a video game has the same problems and forces the child to follow a given set of actions and has only set reactions. Simply put, voices and people represented in ecectronic media do not behave or react like real human beings. What message does this give the child? In response to this, a child disassociates elements that in a human being are whole and all associated together.
Babies and young children do not think yet, they cannot make decisions or pass judgments. Only later, in the pre-teens are children fully able to filter and distinguish between real and un-real. Children misunderstand advertising and distorted behaviour, and are deeply affected by violence. And so, they become desensitized to real human interaction. Repeated exposure to any kind of media for young children can lead to a distancing of themselves from real people in real life situations and can lead to lack of compassion, and more aggressive behaviour. In this way, the media weakens the development of a healthy social sense.
The effects of television viewing, computers and video games cannot be underestimated: they reach far into the foundation of the child's relationship to the world. They affect the child's values, their relationship to and estimation of other people, their relationship to themselves, their perception of reality. Also, children's programs, cartoons and education shows are not only violent in some cases, but they expose the child to behaviour that both shows lack of reverence and respect for other people, or encourages awareness of self image, which jars the child into growing up before her time. Not to mention the enormous impact and very researched field of the short-term and long-term effects of violence in the media. Regardless of the content watched, television, films and computer games are addictive, impoverish creativity and imagination, as well as keeping them sitting in front of a screen instead of moving and playing.
There is a very common fear that a child who has little or no exposure to media, will be left behind other children and be socially excluded. But when the time comes that the child will really need to use an electronic device, she will be quick to learn and most likely be very enthusiastic to learn. Even as an adult, one can quite quickly learn the basics of using a computer, more so all the time, as computers become more user-friendly. As for social inclusion, there may be a time when the child isn't as plugged-in to the latest and what's in - but this is very quickly learned if it's really important to know - there is a whole industry out there making sure everyone knows what there is to know! So I think it is safe to trust that children have very little difficulty in learning and adapting. As for being socially excluded, when children are old enough to want friends, they usually find friends they can relate to. This is something that can be encouraged by inviting friends to play and encouraging healthy play without media.
Since electronic media is so much part of modern life, it can be a huge challenge to avoid exposing young children and babies to it. One thing that helps immensely is to start by weaning oneself from it. Try to watch less TV, to spend less time on the computer, and put down your smartphone. Try pick up singing, (no matter how out of tune you are) and learn to play an instrument instead of only listening to music, and be selective and attentive to content when playing music around the child.
Using the television or films as a babysitter seems to have become a necessity in some situations. It may help to really look at the situation and see if the child could in some way be involved in what you are doing, or if there is something else you can show them or give them to do while you accomplish your task. Sometimes having a special book or a paper bag full of special things (with a one year old it can even be cans from the kitchen cupboard) that you give them to hold their attention for a few minutes.
In weaning oneself, a good first step is to be aware of when one does check messages, watch TV, play games, and listen to the radio. Try to have set hours of screen time. It can be interesting to keep a log of when and for how long the TV is watched, how much the smartphone is checked, how often you go to your device. Be honest with yourself and really look at the reasons for turning on the radio, the TV, the computer, checking your phone. Often, it's out of tiredness or habit we turn to our devices, wanting to get away from frustrations of life, or we spend time on the computer to answer a few emails, look something up or play a game, and find that three hours have gone by. We fill our lives with music we often don't listen to... why? If you know the reason for it, see if you can find something inspiring to do instead. Taking televisions and computers out of children's rooms is a good start to reducing screen time. Eventually, it may help to put the computer in a place it can easily be monitored, and the television somewhere less central in the house or hidden from view. You can even take the plunge and stop cable or satellite service, use the TV only for watching films, or simply, if you can do it, get rid of it. It may also be a good idea to make a plan or a list of activities to do instead of watching television or going to the computer, so you have something to refer to when temptation strikes. Look for new ways of finding entertainment, of spending time together or alone, of doing things that enrich life and bring learning experiences about the world.
See articles from
Commercial Free Childhood and University of Michigan Television and Children
A list of research studies about TV and children at Active Bodies Active Minds:
Documentary film Consuming Kids
 American Academy of Pediatrics (AAP) TV and Toddlers <http://www.aap.org/sections/media/toddlerstv.htm> and Healthy Children <http://www.healthychildren.org/English/family-life/Media/Pages/Where-We-Stand-TV-Viewing-Time.aspx>from Caring for Your Baby and Young Child: Birth to Age 5 American Academy of Pediatrics Elk Grove Village, IL 2009 . researched October 2011
 Hancox R.J. et al. Association of television viewing during childhood with poor educational achievement. Archives of Pediatrics and Adolescent Medicine Vol. 159 No. 7 July 2005 researched October 2011 <http://archpedi.ama-assn.org/cgi/content/full/159/7/614>
 Sigman, Aric, Dr. Remotely Controlled - How Television is Damaging our Lives. Vermillion, London, 2007 pages 29, 30
 Christakis Dimitri A., MD, MPH, et al.. Audible Television and Decreased Adult Words, Infant Vocalizations, and Conversational Turns A Population-Based Study. Archives of Pediatrics and Adolescent Medicine Vol.163 No.6, June 2009, researched June 2009 <http://archpedi.ama-assn.org/cgi/content/abstract/163/6/554>
 Gentile, D.A. Walsh. A normative study of family media habits. Applied Developmental Psychology 23 (2002) 157–178 2002, January, 2002, researched June 2009 <http://www.mediafamily.org/research/report_g_w2002.pdf>
 Sigman, pages 13 -52
 Jusoff, Kamaruzaman. Television and Media Literacy in Young Children: Issues and Effects in Early Childhood. Canadian Center of Science and Education, International Education Studies Journal Vol. 2 No. 3 August 2009, researched Sept. 2011 <http://www.ccsenet.org/journal/index.php/ies/article/view/3339/3005>
 Hecht, Frederick M.D. and Barbara K. Hecht, Ph.D.. Attention Problems Due to TV Before 3.Medicine Net.com, 5 April 2004, researched June 2009 <http://www.medicinenet.com>
 Sigman, pages 29,39
 Hancox RJ. Association between child and adolescent television viewing and adult health: a longitudinal birth cohort study. NCBI Pub Med www.pubmed.gov, 17 July 2004, researched August 2009 <http://www.ncbi.nlm.nih.gov/pubmed/15262103?dopt=AbstractPlus>
 Josephson, Wendy L. PH.D.. Television Violence: A Review of the Effects on Children of Different Ages. Health Canada, Ottawa 1995
 Parker-Pope, Tara. TV Background Noise Disrupts Child Play. New York Times, Health, 7 July 2009, researched July 2009, <http://well.blogs.nytimes.com/2008/07/16/tv-background-noise-disrupts-child-play/>
 Acoust. J. Community noise exposure and stress in children. Acoustical Society of America Digital Library Soc. Am. Volume 109, Issue 3, pp. 1023-1027, March 2001, researched July 2009 <http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JASMAN000109000003001023000001&idtype=cvips&gifs=yes>
 Maxwell, Dr. Lorraine E. & Dr. Gary W. Evans. Design of Child Care Centers and Effects of Noise on Young Children. Cornell University, 1997, researched July 2009 <http://www.designshare.com/research/lmaxwell/noisechildren.htm>
 Coca, Nithin. The Effects of Media on Children. Associated Content, 9 January 2006, researched June 2009 <http://www.associatedcontent.com/article/16514/the_effects_of_media_on_children.html?cat=9>
 Guernsey, Lisa. Into the Minds of Babes: How Screen Time Affects Children From Birth to Age Five.Basic Books, Philadelphia, 2007
 Wilcox, Brian, PhD, et al.. REPORT OF THE APA TASK FORCE ON ADVERTISING AND CHILDREN. American Psychological Association, 20 February 2004, researched June 2009 <www.apa.org/releases/childrenads.pdf>
 Huesmann, L. R., et al.. Longitudinal relations between children’s exposure to TV violence and their aggressive and violent behavior in young adulthood: 1977-1992. American Psychological Association, Inc. Developmental Psychology, 2003, Vol. 39, No. 2, 201–221, 2003, researched June 2009 <http://www.apa.org/journals/releases/dev392201.pdf>
 Winn, Marie. The Plug-In Drug, Television, Computers and Family Life. The Penguin Group, New York 2002
THE FIRST YEAR