Law of Similarity

A repeated visual treatment suggests a shared meaning.

01 / UNDERSTAND

The idea

Elements that share a colour, shape, size or other visual treatment tend to be perceived as related, even when they are separated by space. People may also expect similar-looking controls to behave in similar ways. Repetition therefore carries meaning, not just visual consistency.

Define which relationships the visual system should communicate. Give the same kind of action or status a consistent treatment and distinguish genuinely different categories. Then look for accidental matches: an ordinary label that looks like a button can invite a click, while two different actions styled identically may hide a consequential difference. Colour can reinforce a category, but a label, icon or shape should provide another way to understand it. Check both the first encounter and repeated use.

02 / RECOGNISE

See it in real products.

Examples of how the principle can appear in an interface.

DuolingoEXAMPLE 01

Make comparable practice options look like comparable choices

Duolingo’s Practice tab presents several practice activities with a repeated row treatment. Their common layout signals that they are options at the same level, while icons and labels identify their different content. Repeated styling supports comparison; the activity names still have to explain the real difference.

Duolingo · Interface exampleProduct reference
AppleEXAMPLE 02

Use one pill treatment for one category of filter

Apple Reminders shows available tags as similarly shaped buttons above tagged reminders. Their common treatment identifies them as a family of filters even when their labels differ. A selected state can then distinguish the active filter, while the words preserve the meaning for people who cannot rely on colour alone.

Apple · Interface exampleProduct reference

03 / CONNECT

Why it matters.

Consistent visual categories may help people recognise related actions and statuses. Test whether they predict behaviour accurately instead of only judging the screen’s consistency.

Possible influences to investigate, rather than guaranteed outcomes for every product.

04 / APPLY

Put it into practice.

  1. 01

    Assign repeated styles to consistent meanings

  2. 02

    Distinguish controls from non-interactive labels

  3. 03

    Pair colour categories with text or another visual cue

05 / EXPLORE WITH UPSLIDE

Apply it with Upslide.

Use a practical guide, read a deeper explanation, or examine a related Upslide project.

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Reviewed by the Upslide team.