inattentional blindness: a standalone construct

Arien Mack and Irvin Rock named the phenomenon in their 1998 book Inattentional Blindness, defining it as the failure to notice a fully visible object or event when one's attention is occupied by another task, so that the object goes unseen not because of any limit of the eye but because it was never attended. Daniel Simons and Christopher Chabris gave the effect its best known demonstration in 1999, the study now called the gorilla experiment, in which many viewers counting basketball passes in a video failed to see a person in a gorilla suit walk through the scene. The construct describes a normal feature of attention rather than a defect of vision: the stimulus falls on the retina and is potentially visible, yet without attention it does not reach reportable awareness. What makes it a landmark is that it separates seeing from attending, showing that focused attention is a condition for the conscious perception of even large, unexpected objects. It is distinct from change blindness, the related failure to notice a change between two views, which concerns comparison across time rather than the noticing of a single unexpected object.[1][2]

Unit

A perceptual outcome: whether an observer notices a fully visible, unexpected stimulus while attention is engaged on a primary task

Recovery means

Not a lasting deficit: the unexpected object is readily seen once attention is directed to it on a repeat viewing

Measured by

Operationalised with a demanding primary task (for example, counting basketball passes) during which an unexpected object appears; identified by whether observers report noticing that object in a post-task question