Test your attention in this classic video by cognitive scientist Prof. Daniel Simons.
All you have to do is to count the number of times the players in WHITE pass the ball.
Note: There is no sound.
This video demonstrates the extraordinary phenomenon of inattentional blindness.
This refers to a failure to perceive something because we do not expect it, and because our attention is focussed elsewhere.
Inattentional blindness is often exploited by magicians who employ misdirection in their performances.
Chabris, C.F. & Simons, D. (2010). The Invisible Gorilla: And Other Ways Our Intuitions Deceive Us
Mack, A. & Rock, I. (2000). Inattentional Blindness MIT Press.