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 — with design applications and failure modes.
Influence (Cialdini)
Authority
Credible voices signal trust
We feel a deep-seated duty to authority. Authority is signaled through three trappings: titles, clothes, and accessories — but real authority is verified through specific domain detail.
Commitment & Consistency
Small yes leads to bigger yes
Once we make a choice or take a stand, we encounter personal and interpersonal pressure to behave consistently with that commitment. The deeper the public or written commitment, the stronger the pressure.
Liking
We say yes to those we like
We most prefer to say yes to the requests of someone we know and like. Liking is built through similarity, sincere compliments, cooperation toward shared goals, and positive association.
Reciprocity
Give first, receive later
We are obligated to give back to others the form of behavior, gift, or service that they have first given to us. The obligation triggers compliance even when the original gift was unwanted.
Scarcity
Limited availability raises perceived value
Opportunities seem more valuable to us when their availability is limited. Scarcity also signals quality and triggers psychological reactance — the urge to act before the option vanishes.
Social Proof
People like me are doing this
We view a behavior as more correct in a given situation to the degree that we see others performing it. Similarity to the proof source amplifies the effect — peer proof beats authority proof for action.
Unity
Shared identity, not just shared interest
The category of "we-ness" — shared identity like family, ethnicity, place, or chosen tribe — is the most potent of all influence factors. Unity is identity, not just similarity.
Habit design (Hooked)
External Trigger
Outside cue prompts action
External triggers communicate the next action through information embedded in them. Four types: paid (ads), earned (PR), relationship (referrals), owned (notifications, email, app icon).
Internal Trigger
Emotion or situation prompts action
When a product becomes tightly coupled with a thought, an emotion, or a preexisting routine, the user experiences an internal trigger. Usually negative emotions: boredom, loneliness, anxiety, uncertainty, FOMO.
Investment
User effort, increasing future use
The Investment phase is where the user puts something into the product — time, data, effort, content, social capital. Investment loads the next trigger and raises switching cost over time.
Variable Reward — Hunt
Unpredictable material rewards
Rewards of the Hunt are the search for material resources and information. Slot machines, news feeds, infinite scroll, Pinterest, Twitter — anywhere the next item is unknown.
Variable Reward — Self
Unpredictable mastery rewards
Rewards of the Self are sought for the intrinsic feeling of mastery, competence, and completion. Game progress, streaks, skill acquisition, leveling up — at varying intervals.
Variable Reward — Tribe
Unpredictable social rewards
Rewards of the Tribe are rewards we seek from other people: feeling valued, attractive, included, important. Unpredictability is the multiplier — guaranteed applause loses potency.
Stickiness (Made to Stick)
Connection
Shared meaning, synchronized moments
Moments of connection deepen our ties with others — with relationships, with groups, with strangers. The most powerful are synchronized in time: we are doing the same thing at the same moment.
Elevation
Rise above the everyday
Moments of elevation transcend the normal course of events. They are literal peak moments: defining experiences with above-average positivity engineered into them.
Insight
Moment of realization
Moments of insight deliver realizations and transformations — the user "trips over the truth" and sees something about themselves, others, or the world they hadn't seen before.
Pride
Recognition and achievement
Moments of pride capture us at our best — moments of achievement, of being seen, of courage. They are about being recognized specifically for what we actually did.
Behaviour (Fogg B=MAP)
Anticipation
Seeking hope, avoiding fear
Anticipation is the motivation lever of hope and fear — what's coming, what could be gained, what could be lost. The clearer the imagined future state, the stronger the pull.
Belonging
Seeking acceptance, avoiding rejection
Belonging is the motivation lever of social inclusion or exclusion — the pull toward a tribe and the fear of being outside it.
Cost Simplicity
How costly is it?
Money is an Ability lever — lower, clearer, or honest cost makes action easier. Hidden cost is felt as a betrayal.
Explicit Prompt
Notification, button, email, timer
An Explicit Prompt is a direct call to action in the moment — the information about what to do next is contained within the prompt itself.
Implicit Prompt
Place, person, situation, emotion
An Implicit Prompt cues action through an association in memory — a place, a person, a situation, or an emotion. The cue lives in the user's environment, not in the product.
Mental Simplicity
How complicated is it?
Mental Capacity is the Ability lever of cognitive effort required — decisions to make, copy to read, options to evaluate, concepts to understand.
Physical Simplicity
How physically demanding is it?
Physical Capacity is the Ability lever of physical effort required to complete the action — taps, scrolls, typing, swipes, movement.
Practice
How familiar is it?
Practice is the Ability lever of prior familiarity — actions we have done before are easier, even if objectively complex.
Sensation
Seeking pleasure, avoiding pain
Sensation is the motivation lever of immediate physical or emotional pleasure or pain. The body responds before the mind decides.
Time Simplicity
How long does it take?
Time is an Ability lever — actions that take less time, or that honestly tell us how much time they'll take, are easier to perform.