Inattentional Blindness

In a famous 1999 experiment, the psychologists Daniel Simons and Christopher Chabris showed people a short video of two teams passing basketballs. Viewers were asked to count the passes made by the team wearing white shirts. Halfway through the video, a person in a gorilla costume walked into the middle of the scene, beat its chest, and walked away. The gorilla was on the screen for about five seconds.

Remarkably, about half of the viewers did not notice the gorilla at all. [A] When they were shown the video again, many could hardly believe that they had missed something so obvious. [B] Simons and Chabris used the term inattentional blindness for this failure to see an unexpected object when attention is focused on something else. [C] The effect is not caused by poor eyesight. [D] Instead, it reflects the way the brain manages attention. Because it cannot process everything at once, the brain filters out much of what does not seem relevant to the task at hand.

Inattentional blindness can have serious consequences. For example, drivers who are talking on the phone are more likely to miss pedestrians or traffic lights, even when they are looking straight at them. This is one reason why many experts argue that using a hands-free phone while driving is not much safer than holding one.