The Mom Test
Book Overview
"The Mom Test" by Rob Fitzpatrick is a practical guide to conducting customer interviews that yield honest, useful information. The title refers to the principle that your interview questions should be so grounded in reality that even your mom couldn't lie to you when answering them.
Core Principle
Don't ask people what they think of your idea — ask them about their life and problems. People will lie (kindly) about your idea, but they can't lie about their own past behavior.
Good vs. Bad Questions
Bad questions (avoid)
- "Do you think this is a good idea?" — people will say yes to be nice
- "Would you use/buy this?" — hypotheticals are unreliable
- "How much would you pay for this?" — speculative
Good questions (use these)
- "Talk me through the last time [the problem] happened"
- "How are you dealing with it now?"
- "What have you already tried?"
- "What's the hardest part about [the situation]?"
Key Rules
- Talk about their life, not your idea
- Ask about specifics in the past, not generalities or opinions about the future
- Listen more, talk less
Signals to Watch For
Bad data (ignore/discount)
- Compliments: "That's really cool!" — feels good, tells you nothing
- Hypotheticals: "I would definitely use that" — not a commitment
- Vague future promises: "We'd probably be interested in that"
Good data (pay attention)
- Specific past behavior: "Last week I spent 3 hours doing X manually"
- Emotional language: "This is the worst part of my week"
- Existing workarounds: "I use a spreadsheet + 2 apps to manage this"
- Concrete commitments: time, reputation, money
Commitment Currencies
Strong signals come when people invest something real:
- Time: agreeing to a follow-up, giving you an intro
- Reputation: introducing you to a colleague or decision-maker
- Money: pre-payment, letter of intent
A conversation without a commitment is just a chat. Push for something concrete at the end.
The Mom Test Rule
If your interview questions could be answered with pleasing lies, you're doing it wrong. Reframe until only honest answers are useful.