Maybe cognitive friction in our reading experiences -- be it in typeface choice or annotation mechanism -- is a good thing.
One of the really tough questions to answer in relation to any technology is: When do you make something easy and when do you make it hard? This problem is perhaps most obvious in the realm of game design, since people get bored by games that are too easy and get frustrated by games that are too hard. So game-makers have to learn to split the difference, which in practice means alternating between the easy and the hard. You allow gamers to get some momentum and confidence by completing easy tasks, which helps them to push through the annoyance and even anger that can arise when a nearly intractable challenge comes their way.
But this problem occurs in other technological arenas too. Consider typography, of all things. In his recent book Thinking, Fast and Slow -- which is fascinating in more ways than I can tell you right now -- Daniel Kahneman explains research that has been done on the cognitive burdens placed on us by various type designs. A well-designed text, with a highly legible typeface and appropriate spacing, places a considerably lighter cognitive burden on us than a badly designed page. It works in conjunction with other factors, of course -- but it matters:
A sentence that is printed in a clear font, or has been repeated, or has been primed, will be fluently processed with cognitive ease. Hearing a speaker when you are in a good mood, or even when you have a pencil stuck crosswise in your mouth to make you "smile," also induces cognitive ease. Conversely, you experience cognitive strain when you read instructions in a poor font, or in faint colors, or worded in complicated language, or when you are in a bad mood, and even when you frown.
Reading a page done right is like sliding on the ice: we just flow right along. Take a look at this smart post by Dan Cohen on how much we value cognitive ease when reading, and how many recent tools provide it for us.
However, as Kahneman also points out, flowing right along isn't always the best recipe for understanding:
Experimenters recruited 40 Princeton students to take the CRT [Shane Frederick's Cognitive Reflection Test]. Half of them saw the puzzles in a small font in washed-out gray print. The puzzles were legible, but the font induced cognitive strain. The results tell a clear story: 90% of the students who saw the CRT in normal font made at least one mistake in the test, but the proportion dropped to 35% when the font was barely legible. You read this correctly: performance was better with the bad font. Cognitive strain, whatever its source, mobilizes System 2 [slow, conscious, laborious thinking], which is more likely to reject the intuitive answer suggested by System 1 [the immediate, unreflective thinking by which we make most of our minute-to-minute judgments].
I think about the value of cognitive strain, or as I sometimes call it cognitive friction, when I'm annotating texts. As many people have noted, today's e-ink readers allow annotation -- highlighting and commenting -- but in a pretty kludgy fashion. It can take a good many clicks to get a simple job of highlighting done. By contrast, touch-sensitive tablets like the iPad and the Kindle Fire make highlighting very easy: you just draw your finger across the text you want to highlight, and there: you're done.
Nice. But I prefer the kludge. Why? Because I remember what I'm reading better if the process of highlighting is a tad slow. It may also help that when I highlight on a tablet my hand tends to cover much of the text I'm highlighting, whereas on an e-ink reader my hand is off to one side and I can focus my attention on the text even as I click to draw lines under it. (It's not relevant to this particular post, but on e-ink Kindles you can highlight across page breaks, which cannot now be done on touchscreen devices. Sometimes I have to shrink the typeface to finish a highlight. Very annoying.)
For the very same reason I prefer underlining in codex books with a pencil rather than a highlighter: the highlighter is just too smooth, whereas I have to take some care to underline accurately when I'm using a pencil: there's a degree of manual strain that accompanies and encourages the cognitive strain.
E-books are in their infancy now: there's little textual design to speak of, typography is often terrible, illustrations are limited, errors are shockingly frequent. They'll get much better. But it would be cool if, when they improve, readers were given means of introducing a bit of cognitive friction when that would make the reading experience a stronger one. Sort of like cranking up the speed and increasing the incline on an elliptical trainer.