A viral app idea — "block your AI tools until you photo-prove you did your habits" — is a textbook commitment device: a choice you make now that restricts your future self's options. Economists have studied these since Thomas Schelling's work in the 1980s, and they work because they attack the exact moment willpower fails.
Drag the model to rotate. Each column is a week; height = automaticity gained that week. The sphere tracks your current habit strength on the curve.
Why blocking works
Behavior change fails at the moment of temptation, not the moment of planning. A commitment device moves the decision earlier, when your "cool" system is in charge. The Gatekeeper idea works through response cost: the lazy path (opening Claude) now requires the effortful path (do the habit, take the photo) first.
The Philippines SEED savings study is the classic evidence: clients offered accounts they couldn't withdraw from until hitting a goal increased savings by 81% versus control. Restricting your own freedom, voluntarily, can beat willpower.
The automaticity curve
Habits follow an asymptotic curve — early repetitions add the most automaticity, later ones add less. Lally's UCL team modeled it as A = Amax(1 − e−kt). Missing one day barely dents the curve; the study found single missed days had "no significant impact." Quitting for a week does.
Harder habits have a smaller k (slower rise): drinking a glass of water plateaued in ~20 days; 50 sit-ups took >84 days for some participants.
Four commitment devices, ranked by strictness
| Device | Mechanism | Example |
|---|---|---|
| Soft pledge | Social accountability | Telling a friend you'll run daily |
| Temptation bundling | Pair a want with a should | Only listen to your favorite podcast while at the gym (Milkman, 2014: +29–51% gym visits) |
| App gating | Response cost / friction | "Gatekeeper": prove the habit before the app unlocks |
| Hard forfeiture | Loss aversion (money) | StickK-style: miss the habit, your stake goes to an anti-charity |