Note

The “Right” Scrolling Direction on your Computer

3 minute read

The new scrolling behaviour in Mac OSX 10.7 Lion is very interesting to me, because researching about it unfolds an interesting interaction design topic that connects computer science and cognitive psychology, deeply hidden under the habit fog.

First of all, when I installed Lion and after a few discussions with fellow designers, I suddenly remembered the time when I was a freelance and I was also teaching to people that have never touched a computer: “Ok, now if you move the mouse wheel you can move the page up and down. Try moving the page down now”.
Can you guess what happened? — They moved the page up.

Then I found this comment by Larry Tesler (via Gruber):

Most (but not all) study participants expected to position the mouse near the top of the window to bring the content hidden above the top of the window into view. One reason was that they were looking at the top of the window at the time. Another reason was that they were more likely, as their next action, to select content in the upper half of the window than in the lower half. Consequently, we made the upper member of the arrow pair move the content down. With apologies to computer architects, I’ll call the majority whose expectations were met by this decision the “top-endians”.

As you can see, there’s a sequence of small, tiny details that set a standard:

  1. People with some experience had probably already an experience in text terminals, where to move the page down you had to move the cursor up to the edge of the page, and then up again.
  2. When the mouse appeared, we had no scroll wheel. So you had to move the mouse up, and click to reveal the content above.
  3. At the same time the scrollbar was introduced, and inside it has a cursor moving up and down… in the opposite direction of the page, but in the same direction of the arrows at its edges. The message is then clear, and very consistent: the arrow moves the cursor of the scrollbar it belongs to.
  4. This means that when you use a computer, your attention focuses quickly on the scrollbar: you aren’t moving the content, you are moving the scrollbar cursor.
  5. This is why I noticed at times people at their first attempt scrolling in the opposite direction: they tried to move the content, not the scrollbar. Without a previously existing habit and with the mouse wheel disconnecting your attention from the scrollbar since you don’t have anymore to click it, the expectation was all about content.

This sequence of small changes: cursor, button, scrollbar, mouse wheel explains quite well the reasons and the consequences of the HCI choices we did in the early age of computers.

So, while I don’t know why exactly Apple decided to revert the behaviour, it becomes to me obvious that once you take the decision to remove the scrollbar, you lose the only remaining reason why you should scroll in that direction.

However, it’s not so easy.

Millions of people have already the habit of scrolling in the other direction, and it’s frustrating having it reversed. While it’s easier on the trackpad, on the mouse it’s a little harder. Habit is one of the strongest obstacle and one of the first things that anyone designing or building anything needs to acknowledge and address in some way.

So we have a solution that with modern computers works better, but it’s completely against our habit. If you are willing to experiment yourself, I can tell you that it took 3 days of daily usage to exit from the “frustration zone” and about 7 days to be comfortable with the new scrolling. It’s not much, but I guess that most people will prefer to switch the scrolling flag off (System Preferences -> Trackpad -> Scroll & Zoom -> Scroll direction) than change an habit for no real reason.

And about someone you know that almost never used a computer before and maybe has a smartphone… well, probably it’s better to keep the default scrolling direction.
It’s more natural. :)