Glossary

The ease of performing a behavior right now — one of the three factors in the Fogg Behavior Model, measured across time, money, effort, brain cycles, social deviance, and routine.

Designing products that people with disabilities can perceive, operate, and understand. Codified for the web in the WCAG standard.

The curved threshold in the Fogg Behavior Model separating behaviors that fire from those that don’t, plotted on motivation against ability.

Interfaces people find beautiful are perceived as easier to use — polish buys patience and trust, and can mask real usability problems.

What an object’s properties allow a person to do with it — a handle affords pulling, a flat plate affords pushing. Popularized in design by Don Norman.

An invisible set of evenly spaced horizontal lines that text and elements align to, keeping vertical rhythm consistent across columns.

A navigation trail showing where the current page sits in the site hierarchy, letting users jump back up any level.

An eye-scanning behavior where readers skip the first words of each line when successive lines begin with the same word.

Never remove something whose purpose you don’t understand — investigate the reason it exists first, then decide.

Grouping individual pieces of information into larger meaningful units so more fits in working memory — the practical core of Miller’s Law.

The total mental effort a task demands of working memory. Good interfaces reduce it; every extra choice, step, or inconsistency raises it.

The story a user builds in their head about how a system works. Design succeeds when the interface teaches an accurate one.

Nielsen’s heuristic: follow platform and industry conventions so users never wonder whether different words or actions mean the same thing.

Limits that prevent wrong actions before they happen — a plug that only fits one way, a form field that only accepts digits.

Organizations design systems that mirror their own communication structures. Your org chart ships in your product.

Once you know something, you can’t simulate not knowing it — why experts write confusing docs and ship jargon.

An interface deliberately designed to push users toward choices they wouldn’t otherwise make — the manipulative flip side of behavior design.

Encoding data as visual form — position, length, angle, color — so patterns and comparisons can be read at a glance.

The declining quality of decisions after a long run of choices. Interfaces that demand many small decisions burn it fast.

How easily users can find out what actions are possible and where — determined by visibility, signifiers, and feedback.

Productivity soars when system response stays under about 400 milliseconds — the user and computer keep pace with each other.

Ben Shneiderman’s eight rules of interface design: consistency, universal usability, feedback, closure, error prevention, reversal, control, and low memory load.

Nielsen’s heuristic: eliminate error-prone conditions or catch them before the user commits, rather than relying on good error messages.

The predictable paths eyes take across a page — F, Z, layer-cake, spotted — documented through decades of eye-tracking research.

The most common reading pattern on text-heavy pages: two horizontal sweeps near the top, then a vertical scan down the left edge.

The system’s immediate, visible response to a user action — the confirmation that something happened and what it was.

The time to acquire a target is a function of its distance and size. Bigger, closer targets are faster to hit.

Behavior happens when motivation, ability, and a prompt converge at the same moment: B = M · A · P.

A complex system that works has invariably evolved from a simple system that worked. Complex systems designed from scratch don’t work.

Rules describing how perception groups visual elements — by proximity, similarity, closure, continuity, and figure-ground relationships.

The proportion 1 : 1.618, long used to derive layout and typographic scale relationships that feel naturally balanced.

When a measure becomes a target, it ceases to be a good measure. Metrics optimized directly get gamed.

The gap between what a user wants to do and how the interface lets them do it. Its mirror, the gulf of evaluation, is the gap in understanding what happened.

On evenly weighted layouts, attention flows diagonally from top-left to bottom-right, favoring the primary optical area and terminal area.

Inspecting an interface against a short list of usability principles — a fast, expert-driven complement to user testing.

Decision time grows logarithmically with the number of choices. Fewer, better-organized options mean faster decisions.

It always takes longer than you expect, even when you take into account Hofstadter’s Law.

Nir Eyal’s four-phase loop — trigger, action, variable reward, investment — describing how products build habits.

The cues — labels, links, snippets — users sniff to judge whether a path will lead to what they want. Strong scent keeps them moving; weak scent makes them pogo-stick.

Users spend most of their time on other sites, so they expect yours to work the same way as the ones they already know.

Scanning only the headings and subheadings of a page, skipping the body text between them — the reward for good heading hierarchy.

The section-level menu showing a page’s siblings and children, complementing the site-wide global navigation.

The relationship between controls and their effects. Natural mapping — stove knobs arranged like the burners — needs no labels.

What a user believes about how a system works, built from every similar system they’ve used before. Interfaces fail when they fight it.

Working memory holds about seven items, plus or minus two. Chunking is how interfaces respect the limit.

A grid with both columns and rows, creating repeatable modules that give complex layouts consistent structure.

The drive to act — one of the three Fogg factors, fluctuating through pleasure and pain, hope and fear, acceptance and rejection.

The recurring structures — global nav, local nav, breadcrumbs, search, site maps — that let users move through an information space.

Jakob Nielsen’s ten general principles for interaction design, the most widely used checklist in usability evaluation.

A new user’s first guided experience with a product. Mostly an ability problem: cut steps, pre-fill, and show the first win fast.

More options attract attention but depress action and satisfaction — Barry Schwartz’s extension of choice-overload research.

Roughly 80 percent of effects come from 20 percent of causes. In products: most usage concentrates in a few features.

People judge an experience by its most intense moment and its ending, not its average — design the peak and stick the landing.

Be liberal in what you accept, conservative in what you send. Interfaces should tolerate messy input and return clean output.

Task time drops as a power function of repetitions — fast gains early, diminishing gains forever after.

Showing only the options needed now and revealing the rest on demand, keeping each decision small.

The signal that says “do it now” — the third Fogg factor. Without one, even motivated and able users don’t act.

Dieter Rams’ criteria for good design — innovative, useful, aesthetic, understandable, honest, long-lasting, thorough, environmentally friendly, and as little design as possible.

Nielsen’s heuristic: show options rather than making users remember them. Menus beat command lines for occasional tasks.

Dividing a frame into a 3 by 3 grid and placing key elements on the lines and intersections for natural visual balance.

The first and last items in a series are recalled best; the middle sags — position is a memory decision.

The perceivable mark that communicates an affordance — the label, icon, or shading that says “this is clickable.”

A placeholder layout of grey blocks shown while content loads — and the visual language every illustration on this site is drawn in.

Pre-selecting the choice most users want, converting a decision into a confirmation.

Scanning that skips around a page fixating on visually distinct elements — links, numbers, buttons — rather than reading in order.

Time to steer through a constrained path grows with its length and shrinks with its width — the law of tunnels, menus, and sliders.

Every application has an irreducible amount of complexity. The only question is who has to deal with it — the user or the designer.

BJ Fogg’s method of building behavior by shrinking it until it’s almost effortless, anchoring it to a routine, and celebrating immediately.

Bruce Tognazzini’s foundational rules of interaction design, spanning anticipation, autonomy, consistency, and latency.

The handful of symbols users recognize without labels — search, home, cart, settings — earned through decades of consistent placement.

Nielsen’s heuristic: provide clearly marked exits — undo, redo, cancel — so mistakes are cheap to escape.

Nielsen’s first heuristic: keep users informed about what’s happening through timely, appropriate feedback.

Arranging elements by size, weight, color, and position so the eye meets them in order of importance.

When one item differs from its neighbors, it’s the one remembered — the isolation effect behind every accent color.

The Web Content Accessibility Guidelines — the W3C standard organized around four principles: perceivable, operable, understandable, robust.

Perceived change is relative to the starting magnitude — a change users notice at small scale disappears at large scale.

The empty space around and between elements. Not wasted space — it groups, separates, and gives hierarchy room to work.

Performance rises with arousal to a point, then falls — moderate pressure helps, high pressure hurts, especially on hard tasks.

The scanning path on sparse layouts: across the top, diagonally down to the lower left, then across the bottom — where the call to action belongs.

Unfinished tasks are remembered better than finished ones — the open loop behind progress bars and completion meters.