What is Inattentional blindness?
Inattentional blindness is the failure to perceive an unexpected stimulus that is in plain view when attention is focused on another task. It demonstrates that perception requires attention, not just exposure.
How it works
The most famous demonstration is the invisible gorilla experiment: participants instructed to count basketball passes fail to notice a person in a gorilla suit walking through the scene, even though they look directly at it. Inattentional blindness is not a visual deficiency but an attentional one: the eyes register the stimulus, but it does not reach conscious awareness because attention is allocated elsewhere. The phenomenon has serious implications for driving, medical imaging, and security screening.
Applied example
A radiologist looking for lung nodules on a CT scan fails to notice a matchbook-sized image of a gorilla embedded in the scan. 83% of radiologists missed it in a study by Drew et al. (2013), even though eye-tracking showed they looked directly at it.
Why it matters
Inattentional blindness reveals that seeing is not a passive recording process but an active, attention-dependent construction, with implications for safety and design.
