Why We Test

The 2 buttons in the above picture are for a toilet flush. One button does a big flush using lots of water; the other does a smaller flush using less. Using a small flush when that’s all that is needed avoids wasting water and that’s a good thing.

As you can see the 2 buttons are of different sizes. As an interface designer this poses us a problem – which button should trigger which flush? There are 2 options:

  • The big button is for a big flush and the small button is for a small flush
  • Or, we assume the small flush will be used more often so it should have the bigger button to make it easier to use. The less frequently used big flush can have the smaller button.

The problem is that neither approach is ‘wrong’ – each is a valid implementation. That’s why we test – once we have seen how people naturally interact with our product we know which decision we should take.

The above example is quite trivial but it illustrates the point – for any given interaction there are multiple valid interpretations. If we want our products to be enjoyable we need to know which interpretation the majority of people hold. This is especially important for new products – as we develop them we are totally immersed – living and breathing it every day (and night!). We know how it works. When we created the interface, we could see no other way that it could be interpreted. However, as soon as we see someone use our product for the 1st time, all that certainty can be washed away in an instant.

Testing reveals the truth. We don’t test to be proven right or wrong; we test to see how things are.

Share this post:
  • Add to favorites
  • email
  • Digg
  • Reddit
  • del.icio.us
  • Slashdot
  • Google Bookmarks
  • Technorati
  • HackerNews
  • StumbleUpon
  • Twitter
This entry was posted in Usability Bites and tagged , . Bookmark the permalink. Post a comment or leave a trackback: Trackback URL.


  1. Posted May 14, 2010 at 5:14 pm | Permalink

    This question has perplexed me for years. Seriously, ever time I see one of these dual-button toilets, I spend forever trying to work out which one I should press. I think one should have a picture of a shit on it, and the other some piss. Or something like that.

    I’m a bit obsessed with bathroom usability issues. It seems to me that over the last 10-15 years humankind has developed every flashier-looking toilets, sinks and baths, with ever decreasing levels of user-friendliness. And don’t even get me started on train toilets!

    Rather geekily, I’ve blogged about this subject at some length (the sadly-missed NTK newsletter once called me a “usability expert on the toilet”):

  2. Ashley Towers
    Posted May 14, 2010 at 6:34 pm | Permalink

    Oh it’s so true! Those up down left right single taps drive me mad! I don’t know whether I will be getting my hands washed or unlocking infinite lives! Bathrooms are not a place for the usability obsessive!

    Love your post on the train toilets – I’ve been wanting to do a post on those myself – Think I’ll just post a link to yours instead – you’ve captured the pain I feel every time I use one!

One Trackback

  1. By Link: Train Toilet Usability on May 14, 2010 at 6:44 pm

    [...] Sumption in his comment on my post Why We Test included a link to a post he wrote back in 2002 about train toilet usability. I’ve been [...]

Post a Comment

Your email is never published nor shared. Required fields are marked *