The design psychology skills library
27 persuasion and behaviour design skills for product designers: Cialdini's influence principles, the Hooked model, Made to Stick and BJ Fogg's behaviour model — each one starting with what it gets you, then how to apply it and where it fails.
Influence (Cialdini)
Authority
Credible voices signal trust
Replaces claims with credentials the visitor can check, so trust does not rest on tone of voice. They stop leaving to look for a second opinion.
Commitment & Consistency
Small yes leads to bigger yes
Starts with a small yes the user picks themselves, so every later step agrees with who they just said they were. Dropping out begins to feel like contradicting themselves.
Liking
We say yes to those we like
Makes the product sound like someone the visitor would actually talk to instead of a brand broadcasting. They give you attention they would deny a stranger.
Reciprocity
Give first, receive later
Gives something genuinely useful before asking for anything, so the ask arrives with the favour already done. The visitor answers out of obligation, not persuasion.
Scarcity
Limited availability raises perceived value
Makes a real limit visible, so deciding later stops being free. The visitor acts while the option still exists instead of filing it away.
Social Proof
People like me are doing this
Shows the visitor people like them who already chose this, so the decision stops feeling like a bet. Doubt gets answered with evidence instead of more copy.
Unity
Shared identity, not just shared interest
Frames the offer around an identity the visitor already holds, so it reads as ours rather than for sale. They choose you the way they choose their own side.
Habit design (Hooked)
External Trigger
Outside cue prompts action
Makes every notification, email and ad say exactly what to do next, so attention converts instead of evaporating. The user returns on the cue rather than by chance.
Internal Trigger
Emotion or situation prompts action
Ties the product to the emotion the user feels right before they reach for their phone. It gets opened with nothing prompting it from outside.
Investment
User effort, increasing future use
Every save, rating or upload stores value that only your product can hand back. Returning is worth more each time, and leaving starts to cost something.
Variable Reward — Hunt
Unpredictable material rewards
Makes what comes next unknown but worth finding, so looking has a pull of its own. The user keeps going instead of finishing and leaving.
Variable Reward — Self
Unpredictable mastery rewards
Surfaces progress the user did not know they had made, so the reward is who they are becoming. Practice continues without prizes to hand out.
Variable Reward — Tribe
Unpredictable social rewards
Leaves room for recognition that may come and may not, which is what keeps people contributing. Posting stops depending on guaranteed applause.
Stickiness (Made to Stick)
Connection
Shared meaning, synchronized moments
Turns a solitary action into something done alongside other people at the same time. The user stays for the room, not only for the product.
Elevation
Rise above the everyday
Takes the flattest moment of the flow and makes it worth remembering. The experience gets told to somebody else instead of quietly forgotten.
Insight
Moment of realization
Shows the user something true about themselves they had not noticed, and your product is where they saw it. The realisation is what they come back for.
Pride
Recognition and achievement
Recognises exactly what the user did, at the moment they did it. They keep going because being seen once makes the next step worth taking.
Behaviour (Fogg B=MAP)
Anticipation
Seeking hope, avoiding fear
Turns a vague offer into a future the visitor can actually picture, so the next step reads as progress towards it. They stop weighing the click and start wanting what is on the other side.
Belonging
Seeking acceptance, avoiding rejection
Makes joining feel like walking into a room full of people they recognise instead of filling in a form. The visitor acts to be part of something, not to unlock a feature.
Cost Simplicity
How costly is it?
A price that is legible the first time removes the quiet fear of being tricked. The visitor decides on the offer itself instead of hunting for the catch.
Explicit Prompt
Notification, button, email, timer
Puts the next action exactly where motivation and ability meet, so nobody has to work out what to do. The user moves without re-reading the screen.
Implicit Prompt
Place, person, situation, emotion
Attaches the product to something already in the user's day — a time, a place, a feeling — so it gets opened without a reminder. Coming back stops depending on your notifications.
Mental Simplicity
How complicated is it?
Cuts what the decision costs in thinking: fewer options, fewer words, a default that is already right. The user finishes instead of postponing.
Physical Simplicity
How physically demanding is it?
Takes taps, typing and scrolling out of the path until the action costs almost nothing. The people who would have abandoned the form finish it.
Practice
How familiar is it?
Borrows patterns the user already knows, so there is nothing to learn before getting value. The product feels easy on the first visit, not on the third.
Sensation
Seeking pleasure, avoiding pain
Makes a screen carry the real taste, texture or sound of what you sell. The visitor wants the thing instead of merely understanding it.
Time Simplicity
How long does it take?
Says how long it takes and then keeps the promise, so time stops being the unknown risk. The user starts now rather than saving it for a better moment.
The library keeps growing
27 skills are live today, and we add to the library every week — new principles, new design applications and new failure modes, written the same way: what it gets you first.
Train one today