Interesting piece on experiments in "change-blindness" — the brain's refusal to take note of changes in our visual field.
Working with Christopher Chabris at Harvard University, Simons came up with another demonstration that has now become a classic, based on a videotape of a handful of people playing basketball. They played the tape to subjects and asked them to count the passes made by one of the teams.
Around half failed to spot a woman dressed in a gorilla suit who walked slowly across the scene for nine seconds, even though this hairy interloper had passed between the players and stopped to face the camera and thump her chest.
However, if people were simply asked to view the tape, they noticed the gorilla easily. The effect is so striking that some of them refused to accept they were looking at the same tape and thought that it was a different version of the video, one edited to include the ape.
(via Crooked Timber)