The Mom Test: would your mom lie to you about this?

The book's title comes from Fitzpatrick's central diagnostic: a good customer question is one your own mother couldn't lie to you about, even if she loves you and wants to be supportive. If you ask 'do you think this is a good idea?', your mom will say yes to make you happy — that's a bad question, not because moms are especially dishonest, but because all people are.

He contrasts this with questions about specific facts and past behavior — 'when did you last deal with this problem, and what did you do about it?' — which are much harder to answer with a comfortable lie, because they require a concrete, checkable memory rather than a polite opinion.

The test reframes the entire skill of customer interviews: it's not about being clever, it's about structurally removing the opportunity for flattery to substitute for truth.

Takeaway: before asking any customer question, imagine your mom answering it — if she could lie to spare your feelings, rewrite the question.