Simons's original Selective Attention Test video in 1999 became an internet sensation. This video begins by requesting viewers to count the number of times three basketball players pass the ball. Thirty seconds in, a woman in a gorilla suit saunters through the video, stopping to beat her chest before she walks away. Half of the viewers missed her completely. The unexpected appearance of the gorilla is what differentiates inattentional blindness from other failures of awareness due to distraction or attentional failures.
This phenomenon brings greater issues into question. For example, just how reliable are eyewitness testimonies? It's possible, even probable, that witnesses are unable to focus on the full picture during a crime scene. Inattentional blindness studies are uncovering the very real limitations of our attention.