The 2 Must Know Usability Equations

Fitt's Law - it's all about size and position!

Fitt's Law - size and position!

Hick's Law - 7 plus/minus 2!

Hick's Law - 7 plus/minus 2!

Ok, so I’m not saying that we need to know the maths, but the underlying principles are important! Fitts’ Law tells us that the time to acquire a target is a function of the distance to and size of the target, so the size of a link area and it’s position on the page (and relative to other elements) is important.  Hick’s Law says that the time it takes for a person to make a decision is a result of the possible choices he or she has. More choices mean a longer decision process – which gives us the 7 plus/minus 2 rule.

These are two of the fundamental rules that I use in user experience architecture. I’d recommend Tog’s (Bruce Tognazzini’s) First Principles of Interaction Design for some more.

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An experienced, commercial and creative user experience professional with a proven record in UX leadership, strategy, people management, branding and innovation. Responsible for the design and delivery of several high profile, big brand web sites and enterprise software applications. All opinions here are my own.

2 Responses

  1. Amir D Mar 24, 2009 -

    Regarding Hick’s Law -> Barry Schwartz: The paradox of choice http://www.youtube.com/watch?v=VO6XEQIsCoM

  2. Ian Hickman May 01, 2009 -

    Fitt’s law is essential knowledge for any gui designer.

    One of the 3d modelling packages (I can’t remember which one it is though) shows a great example of this: when you right click you get a star shaped context menu so that all menu options are equal distance away and hence all equally quick to get to.

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