Does television impair intellect?

As I explained in an earlier post, my review-essay “Twilight of the Books” appears in the 24 December 2007 issue of The New Yorker, and as an online supplement, I’m summarizing some of the data that I drew from, organizing the summaries by topic, and including links where I can. These are merely evidence in raw form and are probably a bit indigestible taken en masse. For analysis and discussion and hopefully a more pleasant read, please see the New Yorker article itself.

Yesterday: Is literacy declining? Today: Does television impair academic performance and cognitive development?

There is little doubt that television is on average bad for a person’s intellectual development. If you read through the studies below, however, you will see that there’s some dispute about whether a small dose of the right kind of television at the proper age might be beneficial.

  • A 2001 meta-analysis of data on more than 1 million students found “little room for doubt concerning the negative nature of the overall linear relationship between television viewing and educational achievement.” However, the analysis also suggested that the relationship was not best graphed as a straight line but rather as “an inverted check mark shape,” also called a curvilinear graph. That is, for each age, there is an optimal viewing time, up to which point television viewing is beneficial, and above which it is harmful. The author, Micha Razel, found that this optimum was 2 hours a day for nine-year-olds, 1.5 hours a day for thirteen-year-olds, and 0.5 hours a day for seventeen-year-olds. The benefit of the optimal viewing time decreased with age. Razel found that 55 percent of the students in the data set were exceeding their optimal viewing time by 3 hours a day, and that this excess viewing was lowering academic achievement by about one grade level. Razel speculated that “the finding of a larger optimal viewing time for younger children may be related to their higher quality viewing,” that is, to the probability that they were watching educational programs under parental supervision. [Micha Razel, “The Complex Model of Television Viewing and Educational Achievement,” {link to citation only} Journal of Educational Research, July/August 2001.]
  • In a summary of pre-2002 research, two authors concluded that “educational television has a substantial positive impact and that entertainment television has a negative impact.” The benefit of shows such as Sesame Street has been extensively documented, the authors wrote. One study found that boys who watched educational television at age five had higher grades even in high school (the effect for girls was not statistically significant). On the other hand, a study of the introduction of television into Canada found that its arrival lowered the reading scores of second graders. The positive impact seems to be limited to educational television watched during the preschool and early elementary-school years, and above an optimum level, television watching hampers academic achievement, in a so-called curvilinear graph. Does television displace reading? Educational programs encourage reading, but entertainment programs do displace it in the early, “decoding” stages when reading is an effortful activity. Once reading habits are established, television seems not to affect them. The authors were not persuaded that television shortened attention spans, interfered with homework, taught children to expect all learning to be effortless, or was inherently disabling of cognition. [Marie Evans Schmidt and Daniel R. Anderson, “The Impact of Television on Cognitive Development and Educational Achievement,” Children and Television: Fifty Years of Research, {book available for purchase} Lawrence Erlbaum Associates, 2007.]
  • In a longitudinal study of 330 German kindergarteners and second graders, who were assessed through time-use diaries and achievements tests between 1998 and 2001, researchers found that children who watched entertainment television scored significantly lower on tests of phonological awareness, reading skills, and general achievement, even if their viewing was relatively light. The effect increased as time passed, so that by the third grade, heavy viewers were between one and one and a half years behind light viewers in reading scores. Since light viewers outperformed medium viewers, who in turn outperformed heavy viewers, the study seems to contradict the notion that the relation between television viewing and academic achievement is “curvilinear,” that is, that a certain moderate amount of television is beneficial. (Note that heavy viewers in Germany would be classified as normal viewers in America.) In the German study, the correlation between educational television and test-score gains ranged “from insignificant to moderately positive”—much less substantial than American researchers have found. The researchers controlled for IQ, socioeconomic status, and early literacy. [Marco Ennemoser and Wolfgang Schneider, “Relations of Television Viewing and Reading: Findings from a 4-Year Longitudinal Study,”{link to citation only} Journal of Educational Psychology, 2007.]
  • A survey of 1,008 parents in February 2006 found that babies who were eight to sixteen months old knew six to eight fewer words for each additional hour of baby DVDs and videos watched daily. [Frederick J. Zimmerman, Dimitri A. Christakis, and Andrew N. Meltzoff, “Associations between Media Viewing and Language Development in Children under Age 2 Years,” {link to citation only} Journal of Pediatrics, August 2007. Alice Park, “Baby Einsteins: Not so Smart After All,” Time, 6 August 2007. Lisa Guernsey, “The Genius of ‘Baby Einstein’,” New York Times, 16 August 2007.]
  • Through a re-analysis of longitudinal health data for 1,278 children who were seven years old between 1996 and 2000, researchers found that hours spent watching television at ages one and three correlated with a higher likelihood of attention disorder at age seven. The correlation was present even when the data were controlled for factors such as mother’s drug use or socioeconomic status, and the investigators call the link “robust and stable.” Other researchers, however, have questioned the way that the study’s authors defined attention deficit disorder. [Dimitri A. Christakis, Frederick J. Zimmermann, David L. DiGiuseppe, and Carolyn A. McCarty, “Early Television Exposure and Subsequent Attentional Problems in Children,” Pediatrics, April 2004. Roger L. Bertholf, Steve Goodison, Dimitri A. Christakis, and Frederick J. Zimmerman, “Television Viewing and Attention Deficits in Children,” Pediatrics 2004.] Note: A later Danish study failed to replicate the findings; the study’s authors argue that this may have been because Danish infants watched far less television, and a certain threshold was not crossed by them.

  • The effect of television on cognitive development was studied in a later re-analysis of the Christakis etal. data set, this time focusing on about 1,700 children who were six years old between 1996 and 2000. Hours of television watched before age three caused lower scores on several different cognitive tests. Television watched between ages three and five improved scores on a reading recognition test and a short-term memory test, though not on others. [Frederick J. Zimmerman and Dimitri A. Christakis, “Children’s Television Viewing and Cognitive Outcomes,” Archives of Pediatric and Adolescent Medicine, July 2005.]
  • In a spring 2000 study of 410 third graders in northern California, students with a television in their bedroom scored lower on all tests than those without one, and students with a computer at home scored higher. The lowest scores belonged to students who newly acquired a bedroom television in the course of the study. However, self-reports by the students did not support the hypothesis that television use was displacing homework, in terms of time usage. [Dina L. G. Borzekowski and Thomas N. Robinson, “The Remote, the Mouse, and the No. 2 Pencil: The Household Media Environment and Academic Achievement among Third Grade Students,” Archives of Pediatric and Adolescent Medicine, July 2005.]
  • A September 1999 survey of 4,508 middle school students in New Hampshire and Vermont found that the more time children spent with television and video games during the week, the less likely they were to have excellent grades, and the more likely to have below-average grades. When the data were adjusted to control for covariates such as level of maternal support and child’s rebelliousness, the correlation between television and grades held up, but the correlation between video games and poor academic performance disappeared. In a later letter, the authors suggested that their evidence on video games was weak because few children in the study played video games for as many hours as they watched television, and argued that if they did, the study would have been able to detect video games’ effect on grades. Academic performance was also impaired by having more cable channels available at home, being allowed by parents to watch any kind of content, and being allowed by parents to watch R-rated movies. [Iman Sharif and James D. Sargent, “Association between Television, Movie, and Video Game Exposure and School Performance,” Pediatrics, 2006. Jerald J. Block, Iman Sharif, and James D. Sargent, “Lack of Association between Video Game Exposure and School Performance,” Pediatrics, February 2007.]
  • The effect of television on attention and learning difficulties was studied through interviews with 678 families in upstate New York between 1983 and 2004, when the families’ children were age fourteen, sixteen, twenty-two, and thirty-three. Fourteen-year-olds who watched one or more hours of television daily were more likely to have poor grades, to fail to complete high school, and not to attend college. The effect was present whether the children tested high or low on verbal skills, and whether or not their parents had completed college. Those who watched more than three hours of television a day at age fourteen were even more susceptible to these failures; they were twice as likely not to earn a college degree as those who had watched less than an hour of television a day at age fourteen. Adolescents who watched more television at age sixteen than at fourteen raised their risk of future failure; those who watched less lowered it. When environmental factors were controlled for, learning problems did not in themselves predict future television watching habits. In other words, television was shown to cause academic failure, but not the other way around. [Jeffrey G. Johnson, Patricia Cohen, Stephanie Kasen, and Judith S. Brook, “Extensive Television Viewing and the Development of Attention and Learning Difficulties during Adolescence,” Archives of Pediatric and Adolescent Medicine, May 2007.]
  • The effect of television on long-term academic achievement was studied through interviews with 980 New Zealanders born in 1972 and 1973, starting when they were age five and ending when they were twenty-six. The more television the subjects watched during the week in childhood and adolescence, the more likely they were to leave high school without a diploma, and the less likely to earn a college degree. The effects were present even after adjusting for IQ, socioeconomic status, and childhood behavioral problems. The authors considered it possible that a poor academic experience in high school might have been causing some of the increase in adolescent television watching, but point out that there could not have been any reverse causation at work in the strong correlation between childhood television watching and failure to earn a college degree. The less television a child watched, the better his educational outcome; there was “little support for the hypothesis that a small amount of television is beneficial.” [Robert J. Hancox, Barry J. Milne, and Richie Poulton, “Association of Television Viewing During Childhood with Poor Educational Achievement,” Archives of Pediatric and Adolescent Medicine, July 2005.]

Next: Does internet use improve or impair academic performance? Does it decrease the amount of time spent reading?

UPDATE (27 Feb. 2009): For ease in navigating, here’s a list of all the blog posts I wrote to supplement my New Yorker article “Twilight of the Books”:

Notebook: “Twilight of the Books” (overview)
Are Americans Reading Less?
Are Americans Spending Less on Reading?
Is Literacy Declining?
Does Television Impair Intellect?
Does Internet Use Compromise Reading Time?
Is Reading Online Worse Than Reading Print?
I also later talked about the article on WNYC’s Brian Lehrer Show and on KUER’s Radio West.
And, as a bonus round: Does media violence lead to real violence, and do video games impair academic performance?