Inattentional Blindness: The Invisible Gorilla

The phenomenon is inattentional blindness, a term coined by Arien Mack and Irvin Rock the year before; Simons and Chabris' contribution was to show it lasted for seconds, in a dynamic natural scene, with an object nobody could call subtle. The design descends from Ulric Neisser's 1970s 'selective looking' films, in which a woman with an umbrella strolled through a ball game unnoticed. Two findings sharpen the picture. Observers were far more likely to notice the gorilla when they were counting passes by the black-shirted team than by the white — the unexpected object slips through more easily when it resembles what you have been told to ignore — and a harder counting task made it more likely to be missed. Spatial proximity did not help: the gorilla walked right through the attended region, which suggests attention selects objects and events, not places on the retina. The deeper lesson is the illusion of attention. We experience a rich, complete visual world and assume anything salient would announce itself; in fact we perceive and remember only what receives focused attention, and we badly overestimate how much that covers. Simons and colleagues later named the meta-error — overrating your own ability to detect change — change blindness blindness.