“We can be blind to the obvious, and we are also blind to our blindness.”

Why it was said

Kahneman draws this conclusion in the first chapter of Thinking, Fast and Slow, after describing the 'invisible gorilla' experiment by Christopher Chabris and Daniel Simons, in which many viewers busy counting basketball passes fail to notice a person in a gorilla suit crossing the screen. It sets up a theme the whole book returns to: the limits of our own minds are hard to see from inside.

What it actually means

Missing something is ordinary; attention is limited, and whatever it is not pointed at can pass unseen. The deeper problem is the second half of the sentence. People who missed the gorilla were often sure there had been nothing unusual to see. We do not experience our gaps as gaps; we experience them as a complete picture. That is why feeling certain is weak evidence of being right. The practical lesson is not to try harder to notice everything, which is impossible, but to build in checks from outside your own head: other people, checklists, a second look at a different time.

How to use it

1. 1Before a big decision, ask one person who was not involved to tell you what you are missing.
2. 2Use a checklist for recurring high-stakes tasks, because the step you forget is the one you will not notice forgetting.
3. 3Deniz, an editor at a publishing house in Istanbul, asks a colleague to proofread her final pages; she has read them so many times that her own eyes fill in what is not there.