“The axiom of revelation of preferences states the following:
“You will not have an idea about what people really think, what predicts people’s actions, merely by asking them—they themselves don’t necessarily know.
“What matters, in the end, is what they pay for goods, not what they say they 'think' about them, or the various possible reasons they give you or themselves for that. If you think about it, you will see that this is a reformulation of skin in the game.”
(Source: "How to be Rational about Rationality")