Cobra Effect · Thinking and evidence
Inattentional blindness
Focus hard enough and you miss what is right in front of you.
6 cards, read aloud in 2:14, with a test and sources.
Count the passes. Six people, two basketballs, one minute.
Harvard, 1999. Daniel Simons and Christopher Chabris film three players in white shirts and three in black, weaving and passing. They ask viewers to count the passes made by the white team. Most people get the count about right.
Then they ask whether anyone noticed the gorilla.
Halfway through, a woman in a full gorilla suit walks into the middle of the players. She stops, faces the camera, thumps her chest, and walks off. About half the viewers never saw her. Not a glimpse. Nothing.
That is inattentional blindness.
When your attention is locked on one task, you can look straight at something and not see it. Not forget it. Not see it. Arien Mack and Irvin Rock named it in 1998 after years of quieter experiments with crosses and shapes. The gorilla just made it famous.
They tried it on radiologists.
In 2013, Trafton Drew and colleagues hid a small gorilla in a lung scan and asked experts to look for tumours. Twenty of the twenty four radiologists missed it. Eye tracking showed most of them had looked right at it. Expertise sharpens attention. It does not widen it.
The motorcyclist you did not see.
Drivers looking for cars pull out in front of motorbikes they were staring at. A pilot watching the instruments misses the aircraft on the runway. A manager watching one number misses the whole team quietly quitting. The eyes were open. The attention was spent.
Feeling sure you would have seen it is not evidence.
Nearly everyone who misses the gorilla insists they would have noticed. So build the looking in. Before you decide, ask what you were told to count, and what walked through while you counted. Then get someone who was not counting to look.
Sources
- Gorillas in our midst: sustained inattentional blindness for dynamic events, Daniel Simons and Christopher Chabris, 1999. The original paper, in the journal Perception. Short and readable. Search the title for a free copy, and watch the video before you read it.
- The Invisible Gorilla, Christopher Chabris and Daniel Simons, 2010. The two researchers on the gorilla and five other everyday illusions, from memory to confidence to cause.
- Change blindness, Wikipedia. The sibling finding. People fail to notice large changes in a scene when the change is masked by a blink or a cut, including the stranger they are talking to being swapped for another.
Nearby ideas
- Confirmation bias. We look for evidence that agrees, and rarely test what could say no.
- The availability heuristic. Vivid stories make rare dangers feel common.
- Survivorship bias. The failures you never see can reverse the lesson you draw.
- Post hoc ergo propter hoc. Coming first does not mean causing what came after.
- Correlation is not causation. Two things moving together may share a hidden cause.
- Steelmanning. Argue against the strongest version of a view, not the weakest.
- Choice overload. Too many options that are hard to compare can stop people choosing.
- The razors. Simple rules for cutting away explanations you do not need.