Sleeping Beauty Lab
Probability by experiment
Free · In‑App Purchases · Designed for iPad. Not verified for macOS.
One half or one third? Stop arguing and run it. A live Monte-Carlo lab for the Sleeping Beauty problem and the world of anthropic reasoning. Free, offline, no tracking.
Is the answer one-half or one-third? Sleeping Beauty Lab settles the famous Sleeping Beauty problem the only way that never lies: by running the experiment thousands of times and counting what actually happens.
A coin is flipped. On heads you are woken once; on tails twice, with your memory erased between wakings. You open your eyes. What is the probability the coin came up heads? Halfers say 1/2. Thirders say 1/3. Instead of arguing, watch a live Monte-Carlo simulator tally real awakenings until the numbers speak for themselves.
From that one puzzle, the app opens the whole landscape of anthropic reasoning, the strange logic of reasoning about your own existence:
- Halfer vs thirder, and why each is internally consistent
- SSA and SIA, the two self-sampling assumptions behind them
- The Doomsday Argument and what it really predicts
- The reference-class problem that haunts all of it
- The Presumptuous Philosopher, UN++, Full Non-Indexical Conditioning (FNC), and Anthropic Decision Theory (ADT)
Eighteen interactive screens build the ideas step by step. A betting lab turns abstract credence into concrete wagers, and every claim is backed by experiment or exact arithmetic, never hand-waving.
Features:
- Live Monte-Carlo simulator with adjustable trials
- Benchmark lab comparing strategies side by side
- Day-by-day breakdown of every awakening
- Built-in quiz and a plain-language glossary
Completely free. Fully offline. No account, no ads, no tracking, no data collected. Just you, a coin, and the deepest puzzle in probability.
Whether you are a student, a philosopher, a data scientist, or just argue-at-2am curious, Sleeping Beauty Lab turns a paradox you can debate forever into one you can finally measure.
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The developer, BEK Service LTD, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
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Information
- Seller
- BEK Service LTD
- Size
- 67.8 MB
- Category
- Education
- Compatibility
Requires iOS 15.0 or later.
- iPhone
Requires iOS 15.0 or later. - iPad
Requires iPadOS 15.0 or later. - iPod touch
Requires iOS 15.0 or later. - Mac
Requires macOS 12.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- Remove Ads & Support $1.99
- Copyright
- © 2026 BEK SERVICE LTD