Liqiongyu Lenny Skills Plus Behavioral Product Design

Behavioral Product Design

Scope

Covers

• Turning a desired user behavior into an executable design + experiment plan
• Diagnosing behavior using barriers/drivers (motivation, ability/friction, uncertainty, habit, context)
• Designing behavioral interventions (e.g., defaults, commitment devices, loss aversion/progress, reducing uncertainty) with ethical guardrails
• Producing decision-ready artifacts a PM/Design/Eng team can build and test

When to use

• “Help me apply behavioral science / behavioral economics to this flow.”
• “We need to improve retention / activation / onboarding completion.”
• “Design a streak / habit loop / reminder system (without being spammy).”
• “Users procrastinate (present bias). How do we get them to do the thing?”
• “People stick with the status quo. How do we drive switching/adoption?”
• “Users are uncertain / anxious. How do we reduce uncertainty and move them forward?”

When NOT to use

• You need upstream strategy first (vision, positioning, roadmap). Use defining-product-vision / prioritizing-roadmap.
• You can’t name the target user + target behavior + success metric (this becomes generic advice).
• The goal is to create dark patterns (deception, coercion, addiction, hidden costs). Don’t do this.
• The domain is regulated/high-stakes (medical, financial advice, minors). Require domain/legal review and tighter safeguards.
• You need to design an onboarding flow without a behavioral science lens -> use user-onboarding.
• You need to analyze retention/engagement metrics and cohort data, not design interventions -> use retention-engagement.
• You need to design a survey or research study to collect user data -> use designing-surveys.
• You need to test an existing design with real users -> use usability-testing.

Inputs

Minimum required

• Product context + target user segment
• The target behavior (what user action you want more of, in what context)
• Baseline funnel/retention metrics (even rough) + where the drop happens
• Constraints: platform (web/mobile), notification channels, brand/tone, time box
• Existing evidence: user research notes, support tickets, analytics, session replays (if any)

Missing-info strategy

• Ask up to 5 questions from references/INTAKE.md.
• If answers aren’t available, proceed with explicit assumptions and label unknowns. Offer 2 scopes: narrow (1 behavior) vs broad (journey).

Outputs (deliverables)

Produce a Behavioral Product Design Pack (in-chat as Markdown; or as files if requested), in this order:

1. Context snapshot (goal, segment, constraints, baseline)
2. Target behavior spec (behavior statement + success metric + guardrails)
3. Behavioral diagnosis (barriers/drivers; where bias/friction/uncertainty shows up)
4. Intervention map (ideas mapped to journey moments + mechanism + risk)
5. Prioritized intervention shortlist (top 1–3 with rationale)
6. Behavioral design specs (1–3 build-ready “intervention cards”)
7. Experiment + instrumentation plan (events, primary/guardrail metrics, rollout/rollback)
8. Risks / Open questions / Next steps (always included)

Templates: references/TEMPLATES.md

Workflow (8 steps)

1) Intake + define the target behavior

• Inputs: User context; references/INTAKE.md.
• Actions: Clarify the user, context, and one primary target behavior. Define success + guardrails (what must not get worse).
• Outputs: Context snapshot + target behavior spec.
• Checks: Target behavior is observable and time-bounded (not “be more engaged”).

2) Map the current journey + “moments that matter”

• Inputs: Current flow/JTBD; baseline funnel.
• Actions: Sketch the steps from trigger → action → outcome. Mark drop-offs and emotional moments (uncertainty, effort, waiting, completion).
• Outputs: Journey map summary + top 3 friction points.
• Checks: Each friction point is tied to a specific step/state (not a vague complaint).

3) Run a behavioral diagnosis (barriers + drivers)

• Inputs: Journey moments; evidence; assumptions.
• Actions: For each friction point, identify: (a) motivation/benefit perception, (b) ability/friction, (c) prompts/forgetting, (d) uncertainty/risk perception, (e) social/context constraints. Map likely mechanisms (e.g., present bias, status quo, uncertainty aversion, loss aversion/progress).
• Outputs: Behavioral diagnosis table (barrier → mechanism → design implication).
• Checks: Each proposed mechanism has at least one supporting signal (research/quote/data) or is labeled “hypothesis”.

4) Generate intervention ideas (mechanism-first, not UI-first)

• Inputs: Diagnosis table.
• Actions: Brainstorm 2–4 interventions per priority barrier using the pattern library in references/WORKFLOW.md (defaults, reducing uncertainty, progress/loss framing, commitment devices, reminders, celebration/pause moments).
• Outputs: Intervention inventory (10–20 ideas) with mechanism tags.
• Checks: At least one idea reduces friction (ability) and one reduces uncertainty (trust), not only “add reminders”.

5) Add resilience + reinforcement (without manipulation)

• Inputs: Intervention inventory.
• Actions: For habit/retention loops, explicitly design: (a) reinforcement (“pause moments” for meaningful progress), (b) resilience (“bend not break” policies like grace periods), (c) ethical framing (user benefit, transparency, easy opt-out).
• Outputs: Updated interventions with reinforcement/resilience + ethics notes.
• Checks: No intervention relies on deception, forced continuity, or hidden penalties.

6) Prioritize and pick the top 1–3 bets

• Inputs: Updated inventory; constraints.
• Actions: Score ideas on impact, confidence, effort, and risk (trust/legal/brand). Pick 1–3 that cover different failure modes (friction vs uncertainty vs motivation).
• Outputs: Prioritized shortlist + “why these” rationale.
• Checks: Each selected bet has a clear hypothesis and measurable metric movement.

7) Write build-ready behavioral design specs + experiment plan

• Inputs: Shortlist; references/TEMPLATES.md.
• Actions: For each bet, write an intervention spec: hypothesis, mechanism, UX/copy, states, edge cases, instrumentation, rollout/rollback, and guardrails.
• Outputs: 1–3 behavioral design specs + experiment/instrumentation plan.
• Checks: Engineering can implement without major missing decisions; measurement is feasible.

8) Quality gate + finalize

• Inputs: Draft pack.
• Actions: Run references/CHECKLISTS.md, score with references/RUBRIC.md, and add Risks / Open questions / Next steps.
• Outputs: Final Behavioral Product Design Pack.
• Checks: The pack is specific to this product and can be executed in 1–2 sprints.

Quality gate (required)

• Use references/CHECKLISTS.md and references/RUBRIC.md.
• Always include: Risks, Open questions, Next steps.

Examples

Example 1 (Activation): “New users abandon setup on step 3. Use behavioral science to redesign onboarding and propose 2 experiments.”
Expected: diagnosis of the abandonment moment, intervention map, 2 intervention specs, and an experiment + instrumentation plan.

Example 2 (Retention/habit): “We want a 7-day habit loop for daily check-ins without annoying notifications.”
Expected: habit/reinforcement plan (incl. bend-not-break), celebration moments, a streak spec, and guardrail metrics.

Boundary example (redirect): “We need to analyze our retention cohorts and understand where users are churning.” Response: redirect to retention-engagement -- this request needs metric analysis and cohort diagnostics, not behavioral intervention design. Come back to behavioral-product-design once you know where and why users drop off.

Boundary example (ethical refusal): “Make the UI more addictive so people can’t stop using it.” Response: refuse dark patterns; reframe toward user-beneficial behaviors, transparency, and opt-out controls.

Anti-patterns

Avoid these common failure modes when applying behavioral science to product design:

1. Bias-name-dropping without diagnosis -- Listing cognitive biases (anchoring, loss aversion, social proof) without mapping them to specific friction points in the user journey. Every cited bias must connect to a concrete step where users drop off or hesitate.
2. Notification-as-intervention -- Defaulting to push notifications and reminders as the primary behavior change tool. Notifications address forgetting but not motivation, ability, or uncertainty. Cover all barrier types.
3. Dark pattern disguised as nudge -- Using behavioral techniques to trick users (hidden costs, forced continuity, confirm-shaming). Every intervention must pass the transparency test: would the user agree this helps them if you explained it?
4. Generic habit loop -- Applying a cookie-cutter trigger-action-reward loop without diagnosing the specific barriers for this user segment. Habit design must be grounded in the actual journey data and friction points.
5. Missing guardrail metrics -- Designing interventions to increase a target behavior without tracking unintended side effects (e.g., increased task completion but lower satisfaction, or higher engagement but more support tickets).

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