Want to develop a young reader’s skill? Think ink, not electronic; Gutenberg, not Google. For leisure reading, give elementary or middle school students a book and their reading comprehension rises. Makes sense. But if they curl up instead with electronic devices of any kind for leisure reading, their comprehension actually declines slightly. That’s the important takeaway of a new study in the Review of Educational Research.

Study after study has confirmed the commonsense notion that reading books for fun makes better readers. It’s a virtuous cycle. The more students read, the more they increase their comprehension, their vocabulary and their ability to follow deeper plots and sophisticated ideas. That is, if the young students are reading books. Not so for screens. As the researchers put it: “If a student spends 10 hours reading books on paper, their comprehension will probably be 6 to 8 times greater than if they read on digital devices for the same amount of time.”

What gives? Let’s start with the study itself — “Do New Forms of Reading Pay Off? A Meta-Analysis on the Relationship Between Leisure Digital Reading Habits and Text Comprehension” — a mouthful which, to be fair, I read on a computer screen, but since I’m older — way older — that should be OK (more on that in a minute). Three researchers at the University of Valencia did a statistical analysis of more than two dozen studies of leisure digital reading and comprehension in the past quarter-century that looked at 469,564 readers in all.

Previous research has determined that leisure reading of books or other printed matter contributes to better reading comprehension. However, in this meta-analysis, the researchers focused on electronic devices. They found that for younger readers — those in elementary and middle school — higher leisure reading on electronic devices showed a slightly diminished reading comprehension. For those in high school, college or above, digital leisure reading had a slightly positive association with their reading comprehension. Either way, the magnitude of these relationships is tiny (almost zero) compared to what other studies have demonstrated for print reading habits. This newest study looked at just the results, not the reasons, so we have to make educated guesses about most of them.

Some are obvious: Reading on a tablet or a smartphone can invite distraction. A text message or an emoji might pop up on a screen, diverting young readers’ attention when they need all available brainpower to decipher the text before them. Or the temptations of TikTok or Instagram might prove too much, and a young reader loses focus.

The researchers suggest that the typical substance of electronic leisure reading might hurt reading growth, too. Choppy phrases, uneven spelling, odd punctuation, irregular capitalization, poor grammar and the like that are common on social media and elsewhere online can detract from comprehension, as do apps and websites that invite scanning, skimming and surfing rather than diving into a text and fully engaging it without interruption.

But that’s not all. As the lead author said of using digital devices: “One might have expected that reading for informational purposes (i.e., visiting Wikipedia or other educational websites; reading news, or reading e-books) would be much more positively related to comprehension, but this is not the case.”

In other words, it is also the medium, not just the message. While it was beyond the scope of this study, other research — including another meta-analysis by these same authors — has shown a curious effect. Those who read an article on a printed page comprehend it better than if they had read an exact electronic duplicate on a digital device.

The phenomenon is called the “screen inferiority effect.” Part of the reason may be that humans evolved to do many things, but reading isn’t one of them. That means teaching our brain to read requires what computer programmers call a “kludge” — a makeshift workaround — to make it possible. So the tactile feel, the brush of a finger across a book or the soft whiffle of a printed page being turned — or even the mental map of where a phrase or picture was printed in a book held in two hands, all might help the brain to decode — that is, read — those abstract ink scratches on a piece of paper in a way that any electronic device simply cannot.

While older, established readers have already wired their brains to perform this magic (and that’s probably why their leisure reading helps comprehension no matter the medium), young readers aren’t so equipped. They are still learning to read more than they’re reading to learn. And that’s why actual printed pages are so important for them.

We are not going to turn back the page on the digital age, and electronic devices are an essential element of any modern classroom. However, this is an important reminder that if we want young students to become good readers, we should give them books and other material that they can actually touch, hold and read.

Jim Verhulst is deputy editor of editorials at the Times.