I love the five second test for it’s simplicity: Show somebody your page for five seconds, then ask him/her what the person remembers. There is even a free remote testing platform for it.
The five second test is like a bootstrapped eye tracking experiment for one page. But it does not replace other forms of usability testing, not even in an agile setting.
Why it is helpful, IMHO:
If the visitor doesn’t get the main point of a page in five (or maybe ten) seconds it is likely he will just click the back button. To test landing page designs, the test can be very helpful.
I sometimes use it as the beginning of an in-person usability test. The „live“ five second test goes like this:
- Tell the proband she (or he) was searching for something related to your page (and make sure the proband is actually interested in that)
- Tell the proband she clicked on a link (or search result) and lands on the page you are going to show her.
- Show the page and minimize it after a 5-10 seconds. Now ask her what she remembers.
If you tell her in advance that you will give her only seconds, she will probably try to scan as much as she can and just repeat the words afterwards. So do not tell her in advance, it will make the test more realistic.