Explanation
What it is
Behavioural design applies insights from psychology and behavioural economics to influence how people interact with products and systems.
It focuses on shaping user habits and decision patterns by aligning design choices with predictable cognitive triggers. Nir Eyal’s Hook Model — Trigger → Action → Variable Reward → Investment — is one of its most cited formulations, illustrating how digital products can cultivate repeat engagement.
When to use it
- When designing systems intended to support habit formation or sustained engagement.
- When evaluating ethical boundaries between influence and manipulation.
- When auditing how design decisions impact user autonomy and attention.
Why it matters
Behavioural design has transformed how digital products engage users, powering both beneficial experiences (e.g., health tracking, learning apps) and exploitative ones (e.g., endless scroll, attention traps).
Understanding its mechanics — and the debates surrounding Eyal’s interpretation — helps teams apply these techniques responsibly, balancing business objectives with user wellbeing.
Reference
Definitions
Behavioural Design
The practice of using insights from behavioural science, psychology, and design to influence decision-making and habit formation.
Hook Model
A four-step framework (Trigger → Action → Variable Reward → Investment) proposed by Nir Eyal to explain how products build user habits through feedback loops.
Habit-Forming Technology
Digital systems intentionally designed to encourage repeated engagement, often by leveraging variable rewards and psychological triggers.
Ethical Design
A design philosophy that considers the long-term well-being, autonomy, and informed consent of users alongside commercial objectives.
Canonical Sources
- Eyal, N. (2014). Hooked: How to Build Habit-Forming Products. Portfolio Penguin.
- Fogg, B. J. (2003). Persuasive Technology: Using Computers to Change What We Think and Do. Morgan Kaufmann.
- Williams, J. (2018). Stand Out of Our Light: Freedom and Resistance in the Attention Economy. Cambridge University Press.
- Harris, T. (2017). How Technology Hijacks People’s Minds — from a Magician and Google Design Ethicist. Medium.
- Gray, C. M., et al. (2018). “Dark Patterns and the Ethics of Manipulative Design.” Proceedings of CHI Conference on Human Factors in Computing Systems.
Notes & Caveats
- Behavioural design is neutral in theory but value-laden in application.
- Eyal advocates “ethical persuasion,” yet critics argue the same mechanics enable exploitation when tied to attention-based revenue models.
- The field continues to evolve toward pro-social behavioural design, focusing on wellbeing, education, and sustainability rather than addiction or compulsion.
How-To
Objective
Design habit-forming experiences that create genuine user value while maintaining ethical integrity and transparency.
Steps
- Define the desired behaviour
Specify the target habit in observable, measurable terms (e.g., “complete one mindfulness session daily”). - Map the Hook sequence
Identify triggers, actions, rewards, and investments using Eyal’s framework as a diagnostic lens, not a prescription. - Apply ethical filters
Evaluate whether each design element respects autonomy, consent, and wellbeing. Remove manipulative or deceptive triggers. - Prototype and test for intent alignment
Conduct usability tests focusing on user motivation and emotional response rather than mere engagement metrics. - Measure impact holistically
Balance engagement data with wellbeing indicators (e.g., satisfaction, retention without compulsive use). - Iterate with transparency
Make design intentions visible to users through onboarding, notifications, or opt-out controls.
Tips
- Use choice architecture to support, not override, user goals.
- Pair persuasive techniques with friction for reflection — small pauses that let users reconsider automatic behaviour.
- Document design decisions and ethical trade-offs for future review.
Pitfalls
Over-optimising for time-on-platform
Redefine success metrics around outcomes, not minutes.
Treating ethics as an afterthought
Embed ethical reviews early in discovery, not post-launch.
Ignoring emotional side effects
Include psychological safety in user testing scripts.
Acceptance criteria
- Documented Hook Model map with ethical commentary.
- Evidence of user testing validating intent alignment.
- Updated design artefacts reflecting transparent communication of persuasive elements.
Tutorial
Scenario
- A product manager and UX designer at a wellbeing app are redesigning their daily meditation reminder feature.
- They want to increase consistency without using manipulative “streak” mechanics or guilt-based triggers.
- The team applies behavioural design principles inspired by Nir Eyal’s Hook Model but filtered through ethical design practices.
Walkthrough
Decision Point
How can we increase habitual engagement without fostering dependency or anxiety?
→ Decision: employ positive reinforcement rather than variable rewards.
Input/Output
Input
User research shows reminders help users but can feel intrusive.
Output
A redesigned notification flow with user-adjustable frequency and a tone that emphasises self-kindness.
Action
The designer maps the Hook Model:
- Trigger: Optional daily reminder.
- Action: User opens app and completes session.
- Reward: Immediate feedback (“Nice work — you’ve given yourself a moment of calm”).
- Investment: Progress log for personal reflection (not gamified).
Error Handling
Issue
Early tests reveal some users disable notifications entirely.
Response
Introduce an onboarding step explaining how reminders can be personalised or muted — reframing the feature as supportive, not coercive.
Closure
The updated feature launches with a transparent explainer: “Reminders are designed to help you, not pressure you.”
Post-launch data shows engagement improved modestly, but self-reported wellbeing scores rose significantly — indicating healthier engagement, not addiction.
Result
- Before
Users reported guilt or irritation from daily push notifications. - After
Users engage voluntarily with more positive sentiment and longer retention over time. - Artefact Snapshot
Ethical Behavioural Design Canvas — stored in Figma / Confluence for ongoing iteration.
Variations
- If the product targets children or vulnerable groups → add stricter ethical review and guardian consent.
- If business goals require retention metrics → include “ethical guardrail KPIs” (e.g., voluntary retention, positive sentiment delta).