"Everyone noticed"

Start with the headcount. You walked in with the mark, or you made the hop at the kerb, or you sat at the wrong table, and the number that came to you was high. Half the room. Most of the room. The number arrived without you working it out, which is part of why it feels right.

In 2000, Thomas Gilovich, Victoria Medvec and Kenneth Savitsky published a set of studies on exactly this number. They called what they found the spotlight effect. In the first two studies, they asked students to put on a T-shirt with a large picture on the front, in one version a singer chosen to be embarrassing to be seen in, and walk into a room where other students were already working. Afterwards, the wearer was asked how many people in the room would be able to say who was on the shirt. Then the people in the room were asked. The wearers overestimated. An earlier book in this series read the paper in full and reported the numbers, which were that wearers expected about forty-six per cent of the room to have noticed, and about twenty-three per cent had. Roughly double.

The authors' explanation, which they tested in their fourth and fifth studies, is the one this whole book leans on. You start from your own experience, which is rich, because you've been thinking about the shirt since you put it on, and then you adjust for the fact that other people haven't. You do adjust. You just don't adjust enough, because you can't feel how little the shirt means to someone who's reading. The headcount isn't a count. It's your own attention, scaled down a bit and handed to the room.

Now go back to the two numbers from chapter 1. If you did the exercise, you've got a headcount and a shoe count, and I'd expect the same shape, a headcount well above what you saw when you looked. That's one room and one minute and it proves nothing on its own. But it's the same finding, and you got it yourself, which is worth more than mine.