Oh my goodness. I ran into this kick ass article  and video on uxmag.com. In short sometimes design element that are right in front of our face can some times be missed do to a concept in psychology called inattention blindness, or selective attention. The above video is a great demonstration of this phenomenon. UXmag brakes down these 3 key points related to selective attention that are particularly relevant to UX design:

  1. Human visual perception is much more incomplete and inaccurate than most people realize.
  2. More focus in one area means less attention elsewhere.
  3. Expectations manipulate our perceptions.
  4. Motivations manipulate our perceptions.