Not all that long ago, we had a debate in the office about a Flash application we’d seen that allowed the user to scroll through a brochure on their desktop as if it were a paper brochure. Leaving aside the obvious point that we probably all need to get out more, the debate essentially revolved around whether using a familiar metaphor like turning a page was useful for novice users or whether it was a distraction, given that the page turning interrupts the reader’s flow; surely websites and applications should overcome the deficiencies of how we do things in the ‘real world’ rather than replicate them?

I have to admit to having a lot of sympathy for the latter view. In the early days of the internet, many companies were building 3D virtual shopping malls that replicated a real highstreet, but it was the 2D simplicity of using Amazon that won out, by overcoming the deficiencies of the real high street. 

Apple’s iBooks application has gone down the route of allowing users to swipe between book pages, as if they were real pages, while textbook apps like Inkling break up the text into sections, which the user can then scroll down through, only interrupting their flow at the end of a section. So, what are the advantages and disadvantages of each model?

Swiping as a surrogate for page turning is a familiar model that users will find fairly intuitive. It overcomes the problem that, while scrollbars work well on office documents and webpages, for a long linear document like a novel, the scrollbar shrinks to such a small size that it tells the reader considerably less about the length of the document than a page number would.

Scrolling does have some advantages though; it requires more motor control from the reader to swipe between pages than it does for them to scroll. If turning a page is a familiar model, scrolling is also very familiar, from both the web and desktop applications. For shorter amounts of text, the scrollbar does a better job than pagination, for indicating the length of the document. Finally, Inkling’s designers argue that the very concept of a page is redundant in a digital environment; resize the text size and the entire content will reflow onto a new set of pages, thereby disrupting all the visual milestones the brain puts together when it reads a print book.

In practice, some sort of hybridisation between the two models looks like the most likely outcome. The challenge will be enabling users to work out what model they should use and when. Here are a few snippets from Nielsen Norman Group’s iPad usability research:

“Swiping for the next article is derived from a strong print metaphor in many content apps... The iPad offers no homepages, even though users strongly desired homepage-like features in our testing. (They also often wanted search, which was typically not provided.) In electronic media, the linear concept of 'next article' makes little sense. People would rather choose for themselves where to go, selecting from a menu of related offerings... Using the Web has given people an appreciation for freedom and control, and they're unlikely to happily revert to a linear experience."

"UI pioneer Jef Raskin once used the terms card sharks vs. holy scrollers to distinguish between two fundamentally different hypertext models:
1. Cards have a fixed-size presentation canvas. You can position your information within this two-dimensional space to your heart's content (allowing for beautiful layouts), but you can't make it any bigger. Users have to jump to a new card to get more info than will fit on a single card. HyperCard was the most famous example of this model.
2. Scrolls provide room for as much information as you want because the canvas can extend as far down as you please. Users have to jump less, but at the cost of less-fancy layout because the designer can't control what users are seeing at any given time.

The Web is firmly in holy-scroller camp: users scroll a fair amount and sometimes view information far down long pages. Even mobile-phone apps often rely on scrolling to present more than will fit on their tiny screens. In contrast, card sharks dominate the early iPad designs. There's a bit of scrolling here and there, but most apps try to create a fixed layout for the pretty screen.

There's no real reason we can't have both design models: cards on the iPad and scrolls on the desktop (and phones somewhere in the middle). However, it's also possible that we'll see more convergence and that the Web's interaction style will prove so powerful that users will demand it on the iPad as well.”