A perceptual phenomenon occurs when individuals fail to perceive an unexpected stimulus that is in plain sight. This failure happens because attention is focused on another task, event, or object. Classic examples include experiments where participants focused on counting basketball passes fail to notice a person in a gorilla suit walking across the scene. The limited attentional capacity of the human brain contributes to this effect, where resources are allocated to specific elements of the environment at the expense of others.
The phenomenon highlights a fundamental constraint on human perception and cognition. Understanding this cognitive limitation is crucial in various contexts, ranging from everyday situations like driving to more specialized domains such as air traffic control and medical image analysis. Its exploration has significantly influenced the development of safety protocols and training programs aimed at mitigating the risks associated with attentional failures. Initial research sparked considerable interest in the late 20th century, leading to a wealth of studies exploring its mechanisms and implications.