Half of People Miss a Gorilla in Plain Sight

In 1999, psychologists Daniel Simons and Christopher Chabris ran one of the most famous demonstrations in all of psychology. They asked viewers to watch a short video of two teams passing basketballs and to silently count the passes made by one team. Mid-clip, a person in a gorilla suit walked into the middle of the action, faced the camera, thumped their chest, and strolled off.

Across all 192 observers, 46% failed to report the unexpected event at all. In the harder versions of the counting task, the rate of missing it climbed even higher. The gorilla itself went unnoticed by more than half the people who saw it walk by.

Focusing attention on one thing can render us effectively blind to another in plain view.

The effect is called inattentional blindness: when our attention is locked onto a task, we routinely fail to consciously perceive even large, obvious objects. A 2024 NYU replication of over 1,500 people refined the picture, finding that a faster-moving or leaping gorilla is far easier to spot.