Laws & principles quiz

The laws & principles entries in the glossary, in brief. Open any one for the interactive demo behind it.

Gestalt: proximity

Things close together are seen as a group; things spaced apart are seen as separate. Proximity is one of the strongest cues for grouping - it usually overrides shape or colour, though a shared boundary or visible connection can override it.

Jakob's law

People spend most of their time on other sites, so they expect yours to work like those. Familiar patterns are quicker to use because users already know them - you’re reusing the habits the web has taught them.

Tesler's law

Every process has a minimum complexity that can't be eliminated - only moved. The real question isn't whether to remove it, but who carries it: the user or the team building it. You can see this in action on this page.

Aesthetic-usability effect

The aesthetic-usability effect is our habit of judging better-looking things as easier to use - whether or not they actually are. Polish buys a benefit of the doubt, smoothing over small frictions and making people more forgiving.

Pareto principle

The Pareto principle shows that most impact comes from a small part of the cause - about 80% of value from 20% of the things. In products, a few features drive most use.

Postel's law

Postel's law - the robustness principle - says be conservative in what you send and liberal in what you accept. Take input in whatever shape people naturally give it, then tidy it up yourself, instead of rejecting anything that isn't already perfectly formatted.

Parkinson's law

Parkinson's law: work expands to fill the time given. Give it a week and it takes a week; give it an afternoon and it’s done by tea - often just as well.

Occam's razor

Occam's razor: among designs that solve the problem, the simplest one wins. Don't add elements - options, steps, decoration - beyond what the job needs; every extra is one more thing to read, maintain and get wrong.

Gestalt: similarity

The Gestalt law of similarity tells us we mentally group items that share visual traits - like colour, shape, or size - and perceive them as belonging together, even when spaced apart. Similarity alone suggests they form a set.

Gestalt: closure

Closure is the mind’s tendency to fill in gaps and complete shapes from incomplete visual cues - perceiving a whole circle, triangle, or icon even when only fragments are shown.

Gestalt: continuity

Continuity is the eye's natural tendency to follow smooth, unbroken paths. When lines or rows of elements intersect or branch, you group those that continue in the same direction, not those that merely connect.

Gestalt: common region

Common region is the grouping effect that occurs when items share a boundary: surround some elements with a line or tinted background, and they’ll be perceived as a group - even if other items are closer or equally nearby. It’s one of the strongest grouping cues, alongside visible connections, and typically overrides proximity and similarity.

Gestalt: prägnanz

Prägnanz - the law of good figure - means the mind naturally prefers the simplest, most stable interpretation of what it sees. When faced with ambiguity, you perceive the cleanest version: a few whole shapes rather than many odd ones. You can see this principle in action on this page.

Gestalt: uniform connectedness

Uniform connectedness is among the strongest Gestalt grouping cues: elements joined by a line, or enclosed together, are seen as one group - even when they sit far apart or look nothing alike. A visible connection generally beats proximity and similarity, acting at least as strongly as a shared region.

Gestalt: proximity vs common region

Both group separate items, but in different ways. Proximity groups by closeness - things near each other belong together. Common region groups by shared space - items within one boundary belong together, even if something closer lies outside. When they conflict, the boundary usually takes precedence.