The "invisible gorilla" is a famous psychological experiment that demonstrates selective attention. In the study, participants watch a video of people passing a basketball and are asked to count how many times the ball is passed. Many viewers fail to notice a person in a gorilla suit walking through the scene, highlighting how focused attention can lead to missing unexpected events. This experiment was conducted by psychologists Daniel Simons and Christopher Chabris in 1999. It illustrates the concept of inattentional blindness, where individuals overlook significant stimuli when concentrating on a specific task. The findings emphasize the limitations of human perception and attention.