This goes something like this:

• Look at an interface, it could be a screen you are designing.
• Look away, then look again.

Which parts of the UI feel like they are pushing into your brain - meaning you don't have to think much, you almost instantaneously "get it"?

Example

When I look away and back at this screenshot, I sense the blue highlighted headings are jumping out and into my brain :). It's only after my eyes wander around, that I notice who's the subject of the page.

References

To learn more, see the work of:

Ryan Singer