The human mind and usability part 2: Memory and knowledge

In the second of our series of blog posts looking into psychology concepts that affect design, we look at how our memory works and its connection to knowledge and learning.

Memory and cognitive load

Memory is defined as the ability to store and retrieve information, and can be divided into long-term and short-term memory. Processed information immediately goes into the short-term memory, where it has to be rehearsed in order to go into the relatively permanent long-term memory.

Short-term memory only lasts around 20-30 seconds; that's why when you look up a new telephone number you've usually forgotten it by the end of the call. But the more you practiced or used the phone number, the better you'd be able to remember it.

Our short-term memory store is referred to as our working memory. Working memory is a finite resource, and stimuli from multiple information streams and interactions deplete it, creating cognitive load. As such, cognitive overload reduces our ability to perform tasks well. In other words, the more of your working memory you have taken up with other things, the more difficult it is to work on any one problem.

As I mentioned in [The human mind and usability part 1: Attention][1], most people are already suffering cognitive overload when they arrive at a website -- distracted by children, their phone, Facebook etc. So, when designing a digital experience it's best to avoid putting strain on people's cognitive load by creating an interface that is easy to use, obvious and self-explanatory. One way to do this is to create shortcuts for people wherever possible, rather than expecting users to remember bits of information.

For example, retailers like Topshop understand that mobile users won't always have a pen a paper to hand when using their store locator, so they've created shortcut links between apps to call and get directions, eliminating the need for people to remember the phone number or postcode.

Comparison tools are also a great way to allow people to flag products that they are most interested in without having to rely on their memory.

Tip: When facilitating usability testing, try to have a pen and paper on the desk, but don't point it out to the participant. If they are inclined to use it then your site is relying too heavily on the users short-term memory.

Memory activation and associated priming

When one part of the long-term memory is activated, other memories that are associated with that memory are activated as well. For example if I say British seaside, you might start to think of ice cream, fish and chips and deckchairs (or maybe even rain!).

Associated priming is when exposure to a given stimulus affects your connection to the following stimulus by prompting either positive or negative connotations.

The example above shows an a/b test that was run by Which Test Won to assess privacy related micro-copy within a sign up form. Version A included copy that said "100% privacy -- we will never spam you" where version B had copy saying "We guarantee 100% privacy. Your information will not be shared."

The results: Version B increased sign-ups by 19.47%, where by version A decreased sign ups by 18.70%. Even though version A specifically said it would NOT spam you, the explicit reference to spam created a negative connection that in-turn had a negative impact on sign-up conversion.

This proves that what can sometimes seem like an insignificant detail can have a huge impact on user behaviour -- which is why it's always best to test.

What the Facebook emotional contagion means for A/B testing