I wrote this blog entry when I was considering whether or not to make DS TV-free (and he is):
I started doing research on the effects of television on children. What I found made me realize my gut instinct to keep Henry far, far away was right on. The Plug-In Drug: Television, Computers, and Family Life by Marie Winn is particularly eye-opening. She asserts that it's not just what a child watches that matters -- it's that they watch at all:
"Parents may overemphasize the importance of content because they assume that their children's television experience is the same as their own. But there's an essential difference between the two: adults have a vast backlog of real-life experiences that colors what they see; children do not. As adults watch television, their own present and past experiences, dreams, and fantasies come into play, transforming the material they see into something reflecting their own particular inner needs. Young children's life experiences are limited. They have barely emerged from the preverbal fog of infancy. It is disquieting to consider that hour after hour of television watching constitutes a primary activity for them. Their subsequent real-life activities will stir memories of television experiences, not, as for adult watchers, the other way around. To a certain extent children's early television experiences will serve to dehumanize, to mechanize, to make less real the realities and relationships they encounter in life. For them, real events will always carry subtle echoes of the television world." (Bold mine.)
She also discusses how television watching displaces human interaction for children, and why this is so noteworthy:
"According to...neuroscientists, among the most important of the environmental factors that might affect neurological development are the language and eye contact an infant is exposed to. Indeed, some researchers say that the number of words an infant hears each day is the single most important predictor of later intelligence, school success and social competence. But there's one catch. As a New York Times science writer concluded, 'The words have to come from an attentive, engaged human being. As far as anyone has been able to determine, radio and television do not work.'" (Bold mine.)
Winn says that television viewing also keeps children from playing, which serves a vital role in their social, emotional, and intellectual development. In the "more complex forms of imaginative play they...find ways to work out difficulties and adjust the realities of life to their inner requirements.... In play they expose, and perhaps exorcise, fears that they cannot articulate in any other way."
She also explores the difference between reading and television viewing, which often displaces reading: "At the same time that children learn to read written words they begin to acquire the rudiments of writing. Thus they come to understand that a word is something they can write themselves. That they wield such power over the very words they are struggling to decipher makes the reading experience a satisfying one right from the start." However, "[a] young child watching television enters a realm of materials completely beyond his or her understanding.... They take on a far more powerless and ignorant role in front of the television set than in front of a book."
Winn addresses television's damaging effects on the growing-up process, too: "There's an evolutionary purpose to [the] behavior progression from parent-centered, passive, receptive orientation to an environment-centered, active, learning style of life: the individual's survival in society is necessarily a function of active, adaptive behavior. It is precisely at this point in a child's development, somewhere between the ages of two and thee, that parents are most likely to begin turning on the television set for their young children. While watching television, young children are once again as safe, secure, and receptive as they were in their mother's arms. They need offer nothing of themselves while watching.... Just as they're beginning to emerge from their infant helplessness, the television set temporarily but inexorably returns them to a state of attachment and dependence." (Bold mine.)
Television also negatively affects something called inferential reasoning, Winn says: "One particular skill...that [has shown] a significant decline [among schoolchildren] -- an advanced reading skill called 'inferential reasoning' -- has caused particular concern.... Inferential reasoning is the ability, beyond the mere mechanics of reading, to draw conclusions, form judgments, and create new ideas out of what one reads. The ability to make inferences is essential to meaningful reading in literature, history, science, and other subjects. Without this complex ability, reading becomes a superficial exercise." She gives the example of a project carried out by a Harvard University research organization called Project Zero that connects the decline in inferential reasoning with children's television watching.
The final point I found so compelling in Winn's book is the connection between television and a growing lack of community-mindedness. She says that "[s]tarting in the late 1960s or early 1970s, Americans seemed to grow considerably less community-minded than they had been in years past" and that in "Bowling Alone: The Collapse and Revival of American Community, Harvard social historian Robert Putnam points out that the first television generation was precisely the one that marked the beginning of the decline." Putnam's conclusion was that "'[a] major commitment to television viewing -- such has most of us have come to have -- is incompatible with a major commitment to community life.'" (Bold mine.)
So there you have it. TV makes real-life less real, displaces human interaction, hampers development only produced by play, replaces the power of reading and writing with the passivity of viewing, promotes dependence when independence is crucial, limits the ability to reason inferentially, and narrows the scope of one's involvement in the world.