Chances are, you’ve seen a few change blindness videos before. The clip below is slightly different because it demonstrates how the effect works.
The grey flicker gives just enough time for your visual short term memory buffer to empty. Take it out and it’s easy to notice the difference between the before and after shots. (Read more here, or here)
What’s the implication for UX design? It provides an understanding of the cognitive basis of the yellow fade technique (aka one second spotlight). When you use the web in a natural setting, your eyes are constantly on the move, taking in your environment, blinking, and so on. In doing so, you introduce your own “grey flicker” effect. If something changes in the split second that you glance away, you are going to find it surprisingly hard to notice, just as you found it surprisingly hard to notice the missing engine of the aeroplane in the test above. The animation used in the yellow fade technique helps minimise this problem.