Christopher Chabris and Daniel Simons designed one of the most repeated – and still shocking – psychological experiments.  University students were asked to count the number of passes made between players on one team in a basketball game.  After the video was complete and the total was recorded, the experimenters asked if the students viewing the game noticed anything unusual.  Almost all said no.  The experimenters pressed the viewers further: did they happen to notice the gorilla?  Most students thought this suggestion absurd…until they were shown the video again.  Sure enough, in the middle of the game, a confederate of the experimenters dressed in a gorilla suit enters the basketball court and beats his chest facing the camera before retreating off screen.  The students were flabbergasted.  How could they have missed this?  Chabris and Simon tell us why in their fascinating book entitled The Invisible Gorilla (2011).  It seems that focusing on one particular task renders people incapable of giving attention to anything beyond it.  The illusion of attention helps explain why eyewitness testimony is notoriously unreliable.  The authors go on to explain how memory is similarly unreliable as well as how the least competent people are generally the most confident.  The book is both entertaining and enlightening.