Headstands and Vomit

Crivsola had recognised that a single childhood memory was not enough evidence. She needed to test her prediction — that food comes out when a person does a headstand — on a proper sample of people.

The Sampling Principle

Before running her experiment, Crivsola thought carefully about what it means to test a claim about all humans. You obviously cannot test every human who has ever lived. But you can test a large, representative sample.

When you are making a claim about a large number of things and cannot test that claim on all of them, you can test the claim on a sample representing the population. If the sample is large enough and representative enough, the results should generalise.

Consider the claim that humans have their hearts on the left side of their chest. If you checked a thousand randomly selected humans, you would almost certainly find all of them have their hearts on the left. But in fact, about 1 in 16,000 humans have their hearts on the right. The sample would need to be very large to detect this rare exception.

The Experiment

Crivsola gathered a large group of subjects and asked each of them to eat a meal and then perform a headstand. She watched carefully.

The results were striking: in every single case, food came out of the subjects' mouths during the headstand. The prediction was confirmed — unanimously.

The Surprise

But Crivsola, being a careful thinker, decided to try it herself. She ate breakfast and performed a headstand.

Nothing came out.

She was baffled. Every one of her subjects had expelled food, but she did not. Was she a freak? Was there something different about her body? Or was there something wrong with her experiment?

The Arrest

While Crivsola was doing her headstand — extended, as she tried to understand what was happening — her neighbour Jkopia happened to walk by. In Sonhlagot, there was a peculiar law: only men were permitted to perform headstands, and specifically only men who consumed alcohol.

Jkopia reported Crivsola to the authorities. She was arrested and thrown in jail.

As she sat in her cell, the question gnawed at her: why had all her subjects expelled food during headstands, while she had not? The answer, she suspected, had something to do with who her subjects were. But she would need more information to figure it out.

Fortunately, her cellmate — a factory worker named Lomytguya, arrested for organising a union — was about to provide exactly the clue she needed.