I wrote about this statement before, but now I have something amusing for you to prove that it is cognitively impossible to pretend not to know something, or to act as if you are a novice user.
Humans often have a strong belief in their perspective-taking abilities and especially designers are fast in replying that they themselves are users – so why would they not be able to put themselves in the shoes of the user? [1,2]
A question to you: What do you see in the picture above? At first, it might look like nothing. Look carefully. Then, check out the rest of this post >>>
Now that you know you are looking at the picture of a cow, try to see the original picture as you first saw it. See it as if it does not depict a cow. It is impossible, is it not? You cannot unsee the cow. It is just as hard for developers, product managers and designers to go back to the unknowledgeable state attributed to a novice user.
Now don’t get me wrong: I believe you can have a great idea spring up in you own mind, fed by nothing but your own experiences. But in my opinion, the next step is crucial: Analyse the actual user group and their attitudes. Uncover user behaviour, tasks, contextual circumstances. In short, don’t take your initial idea straight to manufacturing: use User Centered Design cycles to perfect it.
 Mayhew D.J, (1999) The Usability Engineering Lifecycle: A Practitioner’s Guide to User Interface Design. Morgan Kaufmann Publishers