On method: the eight second attention span

Every volume of Principles of Practice ends by naming the number its field repeats most often and explaining why the book does not use it. For marketing that number is the eight second human attention span, usually paired with the claim that it has fallen from twelve, and frequently with the flourish that a goldfish manages nine.

It traces to nothing. Follow the citations and they lead to a consumer insights page, which cites a statistics aggregator, which cites nobody. The researchers most often named have publicly said they did not produce it. There is no goldfish study.

The reason it survives is that it feels true to anyone who has watched a person scroll, and it is enormously useful to whoever is selling shorter content. That combination, intuitively right and commercially convenient, is exactly the profile of a claim that spreads without evidence.

This volume argues something adjacent from a different basis. Attention at first contact really is very short, and the five and fifteen second tests in part one are built on it. But they are offered as a practice you can run and check yourself, on your own material, with your own buyers, not as a constant of human cognition. You can falsify them in an afternoon, which is the point.

The four questions from Volume I apply unchanged. Who produced it and what were they selling. What was the sample and of what population. What exactly was measured, in units. Has anyone independent reproduced it.