Dumb.si
The AI tutor for spotting your own dumb mistakes before you make them
Most bad decisions aren't caused by low intelligence - they're caused by predictable mental shortcuts. Learn the cognitive biases and logical fallacies behind everyday mistakes, and simple techniques to catch them in yourself.
No card required · $9/mo Plus · $99/mo Premium
What you get
Everything Dumb.si gives you
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Bias library
Clear explanations of the cognitive biases behind everyday bad decisions.
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Spot the fallacy
Learn to recognize weak arguments - your own and other people's.
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Debiasing techniques
Practical habits like pre-mortems and decision journals to catch mistakes early.
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Saved study threads
Sign in free and keep every conversation for later reference.
Go deeper
The science of avoiding mistakes
Real cognitive science on why reasoning goes wrong, and how to catch it in yourself.
Cognitive biases
- Confirmation bias — The tendency to notice and favor information that confirms what you already believe.
- Dunning-Kruger effect — A 1999 study finding low-skill people often overestimate their own competence.
- Sunk cost fallacy — Continuing something because of past investment rather than its future value.
- Anchoring bias — Over-relying on the first number or piece of information you encounter when deciding.
Logical fallacies
- Ad hominem — Attacking the person making an argument instead of addressing the argument itself.
- Strawman — Misrepresenting someone's position to make it easier to argue against.
- False dichotomy — Presenting only two options when more actually exist.
Debiasing techniques
- Pre-mortem analysis — Imagining a decision has already failed and working backward to find why.
- Seeking disconfirming evidence — Deliberately looking for information that could prove your belief wrong.
- Decision journal — Recording your reasoning before outcomes are known, to review your judgment later.
Pricing
Simple plans that grow with you
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Plus
$9/mo
- ✓200 questions per day
- ✓Full saved conversation history
- ✓Personalized bias walkthroughs
Premium
$99/mo
- ✓Unlimited questions
- ✓Extended deep-dive answers
- ✓Everything in Plus