The more choices people see, the longer they take to decide.
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Google's homepage: one box, one job, everything else amputated.
McDonald's kiosks show categories first, never all 100 items at once.
Netflix groups thousands of titles into a handful of curated rows — Top 10, Continue Watching — so you never face the full catalog at once.
Source: Hick (1952) & Hyman (1953)
Effort · EXP.02 · Target acquisition
Fitts's Law
Big, close targets are quick to tap. Small, far ones are slow.
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Apple's rule: nothing tappable smaller than 44pt on iOS.
"Place order" is always the biggest thing on screen; "cancel subscription" is a tiny grey link.
Spotify's play/pause button stays large and fixed at the bottom across every view — always an easy, forgiving tap.
Source: Fitts (1954)
Memory · EXP.03 · Working memory
Miller's Law
People can hold only about seven things in their head at once.
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Phone numbers ship pre-chunked: 0300-1234567, never 03001234567.
OTPs are 6 digits, not 10 — past seven, humans drop the packet.
Amazon's checkout breaks address, payment and review into separate short steps instead of one long form that overflows working memory.
Source: Miller, "The Magical Number Seven" (1956)
Memory · EXP.04 · Recall by position
Serial Position Effect
People remember the first and last items in a list best.
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Nav bars put "Home" first and "Sign up" last, never in the middle.
Pricing pages place the plan they want you to buy at the edge of the row.
Duolingo's lesson-complete screen ends on the streak count — the last thing you see, and the thing you remember.
Memory · EXP.05 · The odd one out
Von Restorff Effect
The item that looks different is the one people remember.
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One glowing "Most popular" plan among grey siblings.
A single coloured CTA on an otherwise monochrome page.
On Airbnb, a lone "Guest favourite" badge stands out among similar cards — and it's the detail most people recall afterward.
Decision · EXP.06 · Convention vs chaos
Jakob's Law
People expect your site to work like the sites they already use.
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Logo top-left takes you home — everywhere. You've never read documentation for this.
The cart lives top-right and search is a magnifying glass — imported expectations, not taught ones.
Airbnb keeps search, filters and map where travel sites always put them, so switching from a competitor feels immediate.
Effort · EXP.07 · The 400ms wall
Doherty Threshold
Respond in under 400ms and people stay engaged. Slower, and their mind drifts.
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Spotify's heart and playlist-add icons fill the instant you tap, before any server confirmation returns.
YouTube and LinkedIn paint skeleton screens so the wait feels like progress.
Google autocomplete answers in under 100ms — the interface keeps pace with your thoughts.
Source: Doherty & Thadani (1982)
Behaviour · EXP.08 · Manufactured momentum
Goal-Gradient Effect
The closer people feel to a goal, the harder they push to finish it.
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Netflix's "Continue Watching" row shows a partial progress bar, and that visible incompleteness pulls you back to finish.
"Add Rs. 200 more for free delivery" turns a fee into a finish line.
Spotify Wrapped turns a year of listening into a countdown of milestones, each building anticipation for the next reveal.
Source: Nunes & Drèze, endowed progress (2006)
Perception · EXP.09 · Beauty bias
Aesthetic-Usability Effect
Designs that look good feel easier to use, even when they are not.
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Apple product pages sell perceived quality before a single spec appears.
A polished prototype hides real usability problems in testing — testers forgive beauty.
Airbnb's 2014 redesign: same listings, new polish, and trust metrics jumped.
Effort · EXP.10 · Conservation of complexity
Tesler's Law
Every product has complexity. Someone has to handle it — the user or the system.
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Address autocomplete: you type 5 characters, the system fills 5 fields.
"Sign in with Google" moves the entire password problem to someone else's servers.
Careem and Uber read your pickup point from GPS — complexity absorbed, not deleted.
Design takeaway
Someone always pays for complexity. Good design decides it won't be the user.
Effort · EXP.11 · Be liberal in what you accept
Postel's Law
Accept messy input from people. Give back clean, predictable output.
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Good card fields accept "4242 4242 4242 4242" with spaces and quietly strip them.
Google doesn't scold your typo — it answers what you meant and whispers "did you mean".
A forgiving phone field takes +92, 0092, dashes and brackets, and stores clean digits either way.
Design takeaway
Same data ends up in the database — only one system made it your problem.
Behaviour · EXP.12 · Work expands
Parkinson's Law
A task stretches to fill however much time you give it.
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Booking.com's countdown timers compress your decision into their deadline.
"Only 2 left in stock" manufactures the tight-deadline focus you just felt.
Gmail's "Undo Send" gives a fixed 30-second window; the tight deadline forces a fast decision instead of open-ended second-guessing.
Memory · EXP.13 · Memory of experience
Peak-End Rule
People judge an experience by its strongest moment and its ending, not the average.
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Mailchimp's high-five when you hit send — the peak, engineered.
Airbnb ends a stay with a simple, low-friction review prompt rather than a lengthy survey, so the last impression stays light.
IKEA's exit ice cream: hours of maze, but you leave holding a happy ending that cost them almost nothing.
Source: Kahneman et al., peak-end (1993)
Memory · EXP.14 · The open loop
Zeigarnik Effect
People remember unfinished tasks better than finished ones.
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Netflix's "Continue Watching" row is built on this: an unfinished episode nags at memory in a way a finished series never does.
Cart-abandonment emails work because the unfinished purchase is still nagging you.
That "73% complete" badge on your profile — designed to itch until you scratch it.
Source: Zeigarnik (1927)
Perception · EXP.15 · Gestalt I
Law of Proximity
Things placed close together look like they belong together.
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A form label sits closest to its own field — move it and errors spike.
Price hugs the product photo; float it away and shoppers mismatch items.
Instagram places each caption directly beneath its photo and the username right above it, so proximity alone tells you what belongs to what.
Perception · EXP.16 · Gestalt II
Law of Similarity
Things that look alike seem related, even when they are far apart.
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Every link on a page is the same blue — sameness silently means "I behave the same".
Destructive actions are always red; make one green and watch users delete things.
Spotify styles every playable item — songs, albums, playlists — with the same green play affordance, so similarity signals shared behaviour.
Perception · EXP.17 · Gestalt III
Law of Common Region
Items inside the same border are seen as one group.
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Cards: every dashboard, feed and app store is boxes declaring what belongs together.
Pricing tables draw a border around each plan so features never leak between columns.
WhatsApp encloses each message in its own bubble — that shared boundary groups a multi-line message as one unit.
Decision · EXP.18 · Simplest that works
Occam's Razor
When two designs work equally well, the simpler one wins.
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Google Flights defaults to three fields; the other fifty hide behind one click.
WhatsApp opens straight into your chats — the one thing 99% of opens are for.
Stripe's checkout became the benchmark by deleting every field it possibly could.
Perception · EXP.19 · Gestalt IV
Law of Prägnanz
People see the simplest possible shape, even in a complex image.
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Mastercard is technically two overlapping circles and a lens — you see one simple mark.
Line icons survive at 16px because they're already the simplest possible interpretation.
Google Maps redraws tangled real-world roads as clean simplified lines, because the eye prefers the simplest shape that still communicates the route.
Perception · EXP.20 · Gestalt V
Uniform Connectedness
A line connecting two things groups them more strongly than colour or spacing.
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Checkout steppers: dots joined by a line read as one journey, not four labels.
Org charts and flow diagrams: the connector line is the information.
Figma's prototype connections draw a literal line between two frames — that connector turns two separate screens into one understood flow.
Decision · EXP.21 · The jam problem
Choice Overload
Show too many options and people pick nothing at all.
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The original jam stand: 24 flavours drew a crowd, 6 flavours sold ten times more.
Netflix pushes curated rows because the full catalog is where decisions go to die.
Smart restaurant menus mark "chef's picks" — a shortlist inside the longlist.
Source: Iyengar & Lepper, the jam study (2000)
Memory · EXP.22 · Packets for the brain
Chunking
Break information into small groups and it becomes easy to remember.
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Card numbers render in groups of four: 4242 4242 4242 4242.
IBANs get spaced into blocks because 24 raw characters are unreadable.
WhatsApp displays phone numbers in spaced country-code chunks — grouped digits are far easier to read and verify.
Effort · EXP.23 · The clutter tax
Cognitive Load
Every extra thing on screen uses up a bit of the user's mental energy.
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Nearly every "clean redesign" case study that lifted conversion: same features, lower tax.
Google's homepage outlived busy 2000s portals that buried search under widgets and news.
Airline sites tuck 30 filters behind one "Filters" button so the fare list can breathe.
Perception · EXP.24 · The invisible gorilla
Selective Attention
When people focus on one task, they stop seeing everything else.
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Banner blindness: users have learned to unsee anything shaped like an ad.
A user hunting the "Continue" button will walk straight past your inline error message.
YouTube's subtle "Skip Ads" button is easy to miss for a first-time viewer focused on their video — focused attention makes everything else fade.
Source: Simons & Chabris, the invisible gorilla (1999)
Behaviour · EXP.25 · Nobody reads the manual
Paradox of the Active User
People start using products right away. They do not read instructions first.
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Onboarding is skippable everywhere, because everyone skips it.
Empty states now teach ("Create your first project") — the manual, smuggled into the flow.
Notion teaches through empty-state prompts like "Type '/' for commands" right where you'll act, because users dive in and never read a manual first.
Source: Carroll & Rosson (1987)
Decision · EXP.26 · The vital few
Pareto Principle
Around 80% of the results come from 20% of the features.
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The iPhone camera: one shutter button carries 80% of use; pro controls hide a swipe away.
Microsoft's own telemetry drove the ribbon: a handful of commands dominated everything.
Your TV remote has 40+ buttons. Count how many you've pressed this month.
Perception · EXP.27 · Gestalt VI
Law of Continuity
The eye follows smooth paths. Lines that flow together are seen as one.
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Line charts: you read each series as one flowing line, even where they cross.
Steppers and timelines pull the eye along a single path from start to finish.
Airbnb's search results flow down one continuous vertical column, so the eye keeps scanning naturally without deciding where to look.
Perception · EXP.28 · Gestalt VII
Law of Closure
People see complete shapes, even when parts are missing.
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Loading spinners: an arc with a gap still reads as a circle in motion.
Logos built from incomplete shapes that your brain finishes on its own.
Netflix crops the last thumbnail in each row at the screen edge; your brain completes the hidden card, and that incompleteness signals "swipe for more."
Perception · EXP.29 · Gestalt VIII
Figure-Ground
People split every scene into a subject and a background.
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Modal overlays: dimming the page pushes it to ground so the dialog becomes the figure.
Negative-space logos hide a second image in the background, like an arrow inside a wordmark.
Instagram Stories adds a subtle gradient behind the top icons so they stay the clear figure against whatever sits behind them.
Perception · EXP.30 · Gestalt IX
Law of Symmetry
Mirrored elements are seen as belonging together, as pairs.
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Split-screen layouts: two mirrored halves read as one balanced composition.
Comparison tables: symmetric columns tell you the plans are equals.
iMessage mirrors your bubbles on the right against theirs on the left, so the whole thread reads as one calm, ordered conversation.
The open library
45 interactive entries — the heuristics, biases, nudges and AI phenomena behind everyday decisions. Open any one to read it and see the demo.
All entries
45 entries · 4 shelves
Heuristics
8 entries
Heuristics01 / 45
Availability Heuristic
Availability heuristic explains why easily recalled information feels more likely.
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Heuristics02 / 45
Recognition Heuristic
Recognition can become a decision shortcut.
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Heuristics03 / 45
Scarcity Heuristic
Limited availability can increase perceived value.
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Heuristics04 / 45
Affect Heuristic
Emotions influence perceived risks and benefits.
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Heuristics05 / 45
Representativeness Heuristic
Similarity can override statistical reasoning.
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Heuristics06 / 45
Fluency Heuristic
Ease of processing influences judgment.
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Heuristics07 / 45
Familiarity Heuristic
Familiarity influences preference.
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Heuristics08 / 45
Social Proof Heuristic
People use others' behavior as evidence.
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Biases
20 entries
Biases09 / 45
Confirmation Bias
People naturally seek information that supports existing beliefs.
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Biases10 / 45
Anchoring Bias
The first piece of information strongly influences later judgments.
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Biases11 / 45
Loss Aversion
Losses feel psychologically stronger than equivalent gains.
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Biases12 / 45
Decoy Effect
An inferior option changes preferences between other choices.
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Biases13 / 45
Status Quo Bias
People prefer familiar situations over uncertain alternatives.
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Biases14 / 45
Choice Overload
Too many choices increase cognitive load.
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Biases15 / 45
Framing Effect
The presentation of information changes decisions.
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Biases16 / 45
Endowment Effect
Ownership creates emotional attachment.
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Biases17 / 45
Planning Fallacy
People underestimate time and obstacles.
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Biases18 / 45
Sunk Cost Fallacy
Past investment influences current decisions.
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Biases19 / 45
Availability Cascade
Frequency can be mistaken for accuracy.
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Biases20 / 45
Dunning-Kruger Effect
Limited knowledge can hide awareness of limitations.
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Biases21 / 45
Optimism Bias
People naturally expect better outcomes for themselves.
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Biases22 / 45
Negativity Bias
Negative information receives stronger attention.
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Biases23 / 45
Recency Bias
Recent information is easier to recall.
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Biases24 / 45
Survivorship Bias
Missing data creates incorrect conclusions.
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Biases25 / 45
Authority Bias
Authority signals influence acceptance.
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Biases26 / 45
Halo Effect
One positive trait influences unrelated judgments.
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Biases27 / 45
Mere Exposure Effect
Familiar things feel safer.
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Biases28 / 45
IKEA Effect
Effort increases emotional attachment.
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Nudges
9 entries
Nudges29 / 45
Default Nudge
Defaults reduce effort and strongly influence decisions.
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Nudges30 / 45
Positive Framing Nudge
Positive framing can increase acceptance and motivation.
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Nudges31 / 45
Social Norm Nudge
Humans are influenced by perceived social expectations.
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Nudges32 / 45
High-Touch Outreach Nudge
Human connection can increase engagement.
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Nudges33 / 45
Commitment Nudge
Commitments create psychological pressure to stay consistent.
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Nudges34 / 45
Reminder Nudge
Simple prompts help people overcome forgetfulness.
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Nudges35 / 45
Simplification Nudge
Reducing complexity makes desired actions easier.
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Nudges36 / 45
Feedback Nudge
Feedback helps people understand performance and progress.
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Nudges37 / 45
Choice Architecture Nudge
The structure of choices influences decisions without removing freedom.
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AI phenomena
8 entries
AI phenomena38 / 45
Automation Bias
People may over-trust automated systems and fail to verify recommendations.
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AI phenomena39 / 45
AI Sycophancy
AI systems may optimize for satisfaction rather than accuracy.
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AI phenomena40 / 45
Anthropomorphism Effect
Humans naturally assign human qualities to non-human systems.
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AI phenomena41 / 45
Calibration Failure
Confidence scores can fail to represent true reliability.
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AI phenomena42 / 45
Automation Complacency
Repeated automation success can reduce human attention.
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AI phenomena43 / 45
Prompt Anchoring
Initial instructions shape AI reasoning and outputs.
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AI phenomena44 / 45
AI Authority Bias
AI outputs can receive excessive authority.
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AI phenomena45 / 45
Algorithmic Amplification
Algorithms can amplify patterns, preferences, and information bubbles.
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The one page I wished existed
A study companion for how people actually think — sourced, free, and built by one designer.
Learn UX started with a simple frustration. Studying UX meant opening twenty tabs — Wikipedia, NN/g, research papers, half-right blog posts — and losing the thread every time. Laws were scattered, sources were unverified, and plenty of the explainers just got the science wrong.
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