The National Bureau of Economic Research has begun circulating a report on what seems to be the largest study yet of what happens when you give a kid a computer. The news is not good, as has been reported in the last few days by David Wessel at the Wall Street Journal and by the Freakonomics crew at the New York Times.

The study, conducted by Jacob Vigdor and Helen Ladd at Duke University’s Sanford School of Public Policy, examined extensive data on all public school students in North Carolina between 2000 and 2005 (the data include students’ end-of-year exam scores in math and reading as well as information on how the students spend their time at home). Those years, as the authors note, were a time when home computer use and broadband access were both expanding rapidly. The focus of the research was on students in Grade 5 through Grade 8. The authors write:

The larger sample size available with administrative data – over half a million student/year observations – addresses one common concern with existing studies of the impact of home computer use: low power associated with small sample sizes. The longitudinal nature of the data also permit us to address concerns that students with computer access are a non-random sample of the population by comparing the test scores of students before and after they report gaining access to a home computer, or before and after their local area receives high-speed internet service.

The analysis reveals that home computers have “modest but statistically significant negative impacts” on academic performance as measured by math and reading test scores. In addition: “The introduction of high-speed internet service is similarly associated with significantly lower math and reading test scores in the middle grades.” Worse yet, “the introduction of broadband internet is associated with widening racial and socioeconomic achievement gaps.” Attempts to close the “digital divide” by, for example, subsidizing PC purchases may actually end up widening the divide between rich and poor in academic performance.

The authors are careful to note that there may be gains in other skills related to internet access in the home:

While we find no evidence that this access improves math and reading scores, it is possible that computer and internet access improves important skills that are not directly measured by standardized tests in math or reading. These skills, ranging from the ability to use basic office software to advanced programming or hardware maintenance skills, may be of considerable value in the labor market. While subsidies for home computer or internet access could still be advocated on the grounds that they improve these vocational skills, our results suggest that an additional consequence would be lower math and reading test scores, and wider test score gaps.

Previous studies have shown that students with home computers on average do better academically than students without computers. But that, according to the Vigdor/Ladd study, appears to reflect correlation rather than causation. A home computer is an indicator of general socio-economic advantages, many of which can contribute to relatively strong academic performance. When you look specifically at changes in the performance of individual students over time, Vigdor and Ladd write, “there is no evidence that home computer access improves test scores.” In fact:

Students who obtain access to a home computer sometime between 5th and 8th grade tend to score between 1% and 1.3% of a standard deviation lower on their subsequent math and reading tests. The positive cross-sectional association between home computer ownership and test scores thus reflects the digital divide: those who own computers are in general a positively selected group … Students in ZIP codes that transition from no broadband service to limited service from three or fewer providers post a statistically significant decline in math test scores. The estimated decline is a relatively strong 2.6% of a standard deviation. The impact on reading test scores is more modest and statistically insignificant. Students in ZIP codes that move beyond the four ISP threshold also exhibit modest declines in test scores. The effects are statistically significant, equivalent to 1.4% of a standard deviation in math and 1.6% of a standard deviation in reading.

Comments Vigdor on his blog: “It turns out that access to computers and broadband is, on balance, not good for kids. This is not a super-surprise for those who have followed earlier careful studies on the subject.” In the paper, he and Ladd conclude, “For school administrators interested in maximizing achievement test scores, or reducing racial and socioeconomic disparities in test scores, all evidence suggests that a program of broadening home computer access would be counterproductive.”

As the Freakonomics writers point out, the study is consistent with an earlier study that examined the effects of giving Romanian students access to computers. That study found that “having a computer at home helps kids develop computer skills … But it seems to lower their grades in math and reading.”

Vigdor and Hamm note that the negative consequences of computer use could be tempered if students began to use computers more for homework and less for goofing off. Unfortunately, there’s no evidence that that’s happening. Indeed, as Vigdor points out, “We cut off the study in 2005, so we weren’t getting into the Facebook and Twitter generation.” The opportunities to goof off with computers have expanded rapidly in recent years (and that doesn’t even take into account the explosion of texting on phones). There’s nothing wrong with kids goofing off, of course; what seems to be happening, though, is that the growing amount of time dedicated to goofing off on computers and the net is crowding out time that might otherwise go to studying (or requiring more multitasking while studying).

It is interesting to compare the computer and internet research with new studies which indicate that having books in a home may strengthen children’s academic achievement. One of the studies, published in the journal Research in Social Stratification and Mobility, reveals a strong connection between the number of books in a student’s home and the number of years of education the student completes – and the relationship seems to be more than just a matter of general socio-economic advantages. As the Chronicle of Higher Education reported:

What’s surprising … is just how strong the correlation is between a child’s academic achievement and the number of books his or her parents own. It’s even more important than whether the parents went to college or hold white-collar jobs. Books matter. A lot. The study was conducted over 20 years, in 27 countries, and surveyed more than 70,000 people. Researchers found that children who grew up in a home with more than 500 books spent 3 years longer in school than children whose parents had only a few books. Also, a child whose parents have lots of books is nearly 20-percent more likely to finish college. For comparison purposes, the children of educated parents (defined as people with at least 15 years of schooling) were 16-percent more likely than the children of less-educated parents to get their college degrees. Formal education matters, but not as much as books.

The authors of the study conclude:

Thus it seems that scholarly culture, and the taste for books that it brings, flows from generation to generation largely of its own accord, little affected by education, occupational status, or other aspects of class … Parents give their infants toy books to play with in the bath; read stories to little children at bed-time; give books as presents to older children; talk, explain, imagine, fantasize, and play with words unceasingly. Their children get a taste for all this, learn the words, master the skills, buy the books. And that pays off handsomely in schools.

The other study, to be published later this year, also indicates a strong connection between having books at home and performing well in school, particularly for low-income students. As Salon’s Laura Miller reported, the study “found that simply giving low-income children 12 books (of their own choosing) on the first day of summer vacation ‘may be as effective as summer school’ in preventing ‘summer slide’ – the degree to which lower-income students slip behind their more affluent peers academically every year.”

We need to be concerned about the digital divide, to be sure. But perhaps we should also be thinking about the Gutenberg divide.