Here are several well-known, practical examples of marketing and policy campaigns that used behavioral science principles — what they did, which psychological lever they used, and why they worked.

1. Save More Tomorrow (retirement savings)

• What: Employees commit in advance to increase their retirement contributions when they next get a raise.
• Principle(s): Default/choice architecture, commitment device, inertia, loss aversion.
• Why it worked: Reduces friction and present‑bias by postponing the “pain” of higher contributions and making increases automatic; produced large, sustained increases in savings behavior.

2. Opower / home energy reports

• What: Utilities sent households personalized reports comparing their energy use to similar neighbors and highlighting high performers.
• Principle(s): Social norms, peer comparison, injunctive feedback.
• Why it worked: People want to conform and avoid being “worse than the average,” so many reduced consumption. This is one of the most replicated behavior‑change nudges in utilities.

3. Behavioural Insights Team (UK) — tax‑payment reminders

• What: HMRC letters and emails were reworded to say things like “9 out of 10 people in your area have already paid.”
• Principle(s): Social norms, simplification, salience.
• Why it worked: Social proof and clearer calls to action increased on‑time payments and revenue without changing penalties or incentives.

4. Booking.com / travel sites — scarcity and urgency messaging

• What: Messages like “Only 1 room left” or “14 people are looking right now” shown on listings.
• Principle(s): Scarcity, urgency, social proof, anchoring.
• Why it worked: Creates perceived scarcity and immediate urgency which increases conversion and reduces procrastination.

5. “Share a Coke” (Coca‑Cola)

• What: Replaced the brand logo with individual first names and prompts to “share.”
• Principle(s): Personalization, identity signaling, social sharing.
• Why it worked: Strengthened emotional connection and social sharing, boosting purchase and word‑of‑mouth.

6. Suggested tip/anchor amounts (restaurants, ride‑hailing, POS)

• What: Presenting suggested tip percentages or fixed amounts on payment screens.
• Principle(s): Anchoring, default/choice architecture.
• Why it worked: People tend to pick presented options; average tips rose after adding higher suggested amounts.

7. ALS Ice Bucket Challenge (fundraising via social media)

• What: Short viral challenge that asked participants to either dump ice water or donate — plus nominate friends.
• Principle(s): Social contagion, public commitment, low participation cost, injunctive norm.
• Why it worked: Easy, visible, and social — produced massive reach and large donation spikes.

8. Default/opt‑out organ donation and other opt‑out policies

• What: Moving from opt‑in to opt‑out registration (presumed consent) or defaulting benefits/enrollments.
• Principle(s): Default effect.
• Why it worked: Defaults strongly shape choices; countries and organizations that adopt opt‑out regimes see much higher participation rates (policy rather than single‑ad campaign).

9. Health appointment and vaccine reminders using action prompts

• What: SMS/email reminders that include an implementation intention or simple steps (e.g., “Reply YES to schedule” or “Plan to go on Thursday at 10 AM”).
• Principle(s): Reminders, implementation intentions, simplification.
• Why it worked: Reduces forgetfulness and increases follow‑through by prompting specific plans.

10. Identifiable victim framing in charitable appeals

• What: Fundraising that highlights a single named person/family vs. abstract statistics.
• Principle(s): Identifiable victim effect, emotional salience.
• Why it worked: People give more when a single, relatable person is highlighted than when presented with large, impersonal numbers.

Key practical takeaways for marketers

• Pick the behavior first (what exact action you want someone to take), then choose one or two behavioral levers to test (defaults, social proof, scarcity, commitment, simplification, framing).
• Make desired actions easy and immediate: reduce friction, add clear calls to action, and use smart defaults.
• Use social proof carefully and ethically (accurate norms, not deceptive).
• Test with randomized A/B experiments and measure both short‑term conversions and longer‑term effects.
• Consider ethics and transparency — nudges should preserve choice and not manipulate vulnerable groups.

If you’d like, I can:

• Propose 3 campaign concepts for a specific product/goal using behavioral levers, or
• Create A/B test ideas and messaging templates for one of the examples above. Which would you prefer?