Aesthetic Effect

For an apple, these characteristics might be taste, freshness, or sweetness – that depends on individual taste preferences.

For digital systems or technical appliances, such mislead characteristics very often include its usability!  That means, people tend to rate the usability of a system or product better, if it is aesthetically appealing to them.

No, this is not a good thing! Why is this so critical?

The usability of a system depends on numerous details. Let me name just a few: the system must support user tasks and work-flows, must be perfectly consistent in order not to confuse users, must provide contents only when, where and in the appropriate detail that meets users needs and must be structured to match users mental models. And so much more…

Can any of these usability details be assessed by only looking at the user interface? No, they can’t. You can only detect usability issues, if you carry out tasks and really “use” the system. 

So here is the most crucial learning:

Never ask people how usable they find a system, before they have carried out a number of serious tasks with the system. Otherwise people will rate the usability almost completely on its aesthetic appeal. That does not reflect the systems usability at all and the rating will mostly be better than reality. You get invalid and useless answers, which you better not rely important decisions on!

So always have users carry out a set of real tasks before you ask anything concerning usability!