Decision time

It takes a very cold heart indeed to not love a user-experience concept which can be illustrated using a mathematical formula. Look at Fitts’s law:

T = a + b \log_2 \Bigg(1+\frac{D}{W}\Bigg)

This set of symbols help us understand that the ability to point at something on a screen (or in real life) is dependent on the size of the thing in question and its distance from where you’re currently point (D is the distance, W the width of the thing and T the time it will take to do it).

How do such formulae exist? They show us that we’re dealing with a fundamentally limited but predictable set of capabilities of a fundamentally mechanical end-user. They have real life results, visible in any good mobile phone interface design, no amount of jiggery pokery will change them.

Well it was in this spirit that I stumbled across Hick’s law.

The law is a formula to help show how humans make a choice from a set of available options. Most famously, I suspect, this has been spun off to show that navigation systems should have about 7 options in them.

The idea here is that humans have certain coping strategies for making decisions. If a long list is presented, for example, they will try to create patterns to help them (roughly) bisect the list (pick half and reject half). It has also been shown that decision speed  is related to IQ.

So – whilst we cling to the nice idea that any navigation system will be OK so long as we’ve got no more than 7 items in it, in fact there are several other dynamics at play

* Stimulus / response capability. It will take a lot longer to click on the right link if we break the intuitive link with layout (e.g. “bottom | top| left” is very hard to scan)

* Elements of mixed sorts shown together require the user to read all the labels and think about them together, placing enormous overhead. (“Carbon neutral products / Contact us / Back / About“)

* Users can ignore well known patterns, significantly reducing the thought process.

But the key thing to take away here – which may be very counter-intuitive for you advertising johnnies – is that it is positively in your interests if you can quickly help your users to ignore options which are not relevant to them. Support your user in ignoring messages Smile

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