Linked by Thom Holwerda on Sun 24th Jun 2007 13:44 UTC
Graphics, User Interfaces Federkiel writes: "People working with Apple computers are used to a very consistent user experience. For a large part this stems from the fact that the Lisa type of GUI does not have the fight between MDI and SDI. The question simply never arises, because the Lisa type of GUI does not offer the choice to create either of both; it's something different all along. I usually think of it as 'MDI on steroids unified with a window manager'. It virtually includes all benefits of a SDI and and the benefits of an MDI." Read on for how I feel about this age-old discussion.
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Fitt's Law
by leos on Sun 24th Jun 2007 17:44 UTC
leos
Member since:
2005-09-21

Everyone loves to talk about Fitt's Law, because it's quite well established, and very simple.

Unfortunately, like Thom said, it doesn't take training into account. It also doesn't take inexperience into account. I have never seen an inexperienced computer user take advantage of Fitt's law. Even if the start menu is in the bottom right corner, or the close button in the top right, they still carefully move the mouse cursor on top of the button and click. Fitt's law, while a valuable measure, is not as important as everyone seems to assume.

As for the global application bar, I'm against it, mostly because I do take advantage of Fitt's law, but I very rarely need to access the menus in an application, and would much rather have other functions in the top corners of the screen (minimize and close). If I need to use a function often, it's in a toolbar or a keyboard shortcut. I only very rarely use menus at all.

Thanks Thom for a great article. People need to stop thinking of usability as a black and white issue. I resent desktops which force one interaction model on me and then claim that it is optimal. I decide what is optimal, not them.

Reply Score: 4

RE: Fitt's Law
by RandomGuy on Sun 24th Jun 2007 18:26 in reply to "Fitt's Law"
RandomGuy Member since:
2006-07-30

Unfortunately, like Thom said, it doesn't take training into account.


Oh, it does take training into account but not explicitly.
The general formula "T=a+b*log2(D/W +1)" is the same for trained and untrained but the constant "b" would be a lot lower if you're trained to using this interface.

Let me explain what this means by a simple example:
Let's say we have a 1cm target (W=1) 30cms away from your pointer (D=30). This yields:
T=a+b*log2(31)=a+b*5

"b" could be 1 for a very inexperienced user and 0.1 for a trained user. "a" is probably mainly the reaction time + time needed to decide which button to hit, somewhere between 0.2 and 1s.
Let's say it's 0.3 for the pro and 1 for the noob.

noob: T=1+1*5=6s
pro: T=0.3+0.1*5=0.8s
So our pro could still be 7-8 times faster, all within the mechanics of Fitt's law.

Now let's say the target was 2cm and 10cm away:

noob: T=1+1*log2(10/2 + 1)=3.6s
pro: T=0.3+0.1*log2(10/2 +1)=0.6s

While the pro would still be 6 times faster, he would also be 33% faster than with the smaller target at a bigger distance.
Of course, the noob would be 1.7 times faster so any change in UI layout has the biggest effects on noobs.

So while the influence of Fitt's law is most easily seen for noobs, it is still valid for a trained person.

Edited 2007-06-24 18:30 UTC

Reply Parent Score: 3