Fitts’s Law and Interface Design
How many of you have heard about Fitts’s Law? The opening paragraph in Wikipedia describes it as the time required to rapidly move to a target area, as a function of the distance to the target and the size of the target
. In even more simple terms it means the larger the button and the closer it is the easier you can click it with your mouse, finger, joystick or hockey stick. The smaller it is and the further away the harder it is to click. Which, when you think about it is pretty obvious.
Particletree had a feature article about Visualizing Fitts’s Law (by Kevin Hale) about a year ago which provides a fresher perspective than Wikipedia, but it’s also worth spending 14 minutes listening to Jared Spool’s Usability Tools Podcast: Applying Fitts’ Law.
If you want something to be easy to click then you make it bigger and closer
, as Jared puts it. If you want something to be harder to click then you make it smaller and put it further away
.
Paul Fitts, a psychologist, published Fitts’s Law in 1954 after studying the way people interacted with airplane cockpits. As a model of human psychomotor behaviour it seems to work on just about everything you can think of - including interfaces. Listen to Jared’s podcast, it will make a lot of sense.
September 1st, 2008 at 8:45 am
A simple example of using Fitts’s Law:
Say if you have a set of Quick Links on a home page. Obviously you want users to be able to quickly acquire them with a mouse - therefore larger and closer.
However, if they were to be reduced to thin slivers with tiny text at about 10px, and even go further by pushing these quick links below the fold - then you’ve not only impacted on Fitts’s Law (an actual mathematical model used to measure this kind of thing) but you’ve also impacted by requiring the user to scroll to get there.
My question then is how quick are these quick links supposed to be? Would anyone even bother to use them? And, if they’re not useful then we’d have to rethink them - make them larger and easier to acquire, or drop them from the page design as extra weight.
This is where interface design science has real world effects on graphic designed web pages. We need to think about the user interactions when designing - not just making things pretty.
Also, an interesting article by Smashing Magazine recently on How Simple Web Design Can Help Your Business is worth a read. Less is sometimes more.