Duolingo Habit Design (Behavior Scaffolding)

Confidence: Working. Use ‘streak integrity’ framing and verify retention/MAU metrics with primary sources.

Fit narrative (Problem → Behavior → Solution → Product)

• Problem Market Fit: People want to learn languages but struggle to form durable practice routines.
• Behavior Market Fit: 1–3 minute, guided micro-lessons align with available time and attention.
• Solution Market Fit: Immediate feedback, progress visibility, and weekly rhythms reduce TTFB and support repetition.
• Product Market Fit: Large MAUs and improved retention post-2020 as system matured.

Behavior metrics (window/denominator stated)

• Window: Multi-year; Denominator: active learners.
• MAUs: Large and growing (verify exact numbers and time frames).
• Retention: Document improvements with primary sources; avoid generic claims.

Solution enablement (environment/process)

• Micro-lessons reduce cognitive/temporal load.
• Progress paths and immediate feedback reinforce learning loop.
• Social elements (leaderboards, friend follows) as optional accountability.

Limitations/confounders

• Metrics vary by product version, cohort, and monetization experiments.

Sources

• Company blog and PM analyses; external write-ups.
• Evidence Ledger: BS-0009.