You read 50 per cent less quickly on a standard computer screen than on paper; try to read on a hand-held device such as a PocketPC or Treo and you'll be at 50 per cent less again. On paper we can manage 300 to (at best) 1,000 words per minute; on screen, about 150 words per minute; and on a hand-held, perhaps only 50 to 80 per minute. Your comprehension is generally also lower on work that you read on screen.
The reason for this is straightforward: your eyes have to work harder to make out the words on a screen than on paper; more so on a hand-held. It's all down to "dot pitch", which describes how close together the little spots that make up the picture on screen are.
If you're buying a monitor, get one with a smaller dot pitch; 0.25mm or less is good. The problem with many of the cheaper LCD TVs is that their dot pitch is too high, making the picture grainy.
However, even that 0.25mm level is a long way from the fine detail that paper gives you, where you can get 2,500 dots of ink in every inch (dots per inch, or dpi). Computer monitors manage about 72 dpi, and if you're reading online then you'll have other distractions such as blinking adverts and the need to scroll.
It's that gulf between paper and screen that hobbles our reading, and means that although we may spend hours in front of a screen, the people who print out their e-mails are getting more out of what's there. (Of course, they have to wait for those e-mails to be printed, so they finish the task at the same time as the people reading on their screens.)
The logic of this is inescapable, though. We're looking at more on screen instead of paper, and less of it goes in. That has important ramifications for the way that we try to gather information.
What we need is some "digital ink" - computer screens that have so many pixels crammed on to them that the effect is the equivalent of looking at a piece of paper.
Something heading that way went on sale last year in Japan, with the launch of the Librié from Sony, Philips and a company called E-Ink. Its display offered a resolution of 170 dpi, using positively and negatively charged microscopic white and black beads to form the "ink". Though the Librié is still only on sale in Japan, E-Ink seems to have a promising product that might - perhaps - finally answer the need to be able to read more quickly while getting all the benefits of a computer.
Earlier this month the company showed off a prototype full-colour display with an 83 dots-per-inch resolution - only about 10 per cent better than a normal screen. But the benefits of E-Ink's product is that it can be made flexible, so that it could be incorporated into eminently portable products, and it can give resolutions of up to 100 dpi.
It may be a while before you're reading articles such as these on a computer display on the train. But those days have certainly come a significant step closer.
And if you've been reading this on paper, you can now spend a whole minute that the screen-readers have lost. Just be sure you use it wisely.