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Law of visibility
Necessary objects must be visible without effort so that users can make decisions immediately.
If it is essential, it is on screen. Hidden menus are for the secondary.
If the person has to search, the cost has already been paid, even if they find it. Jakob NielsenWrote the ten usability heuristics and created the heuristic evaluation method that this site treats as triage, not as a test.4 references in this work:199410 usability heuristics for user interface design2000End of Web Design2009Short-term memory and web usability1990Heuristic evaluation of user interfacesSee in the bibliography → put this among the ten usability heuristics in 1994, and the point is simple. Recognising is cheap, remembering is expensive. An action hidden behind a menu or below the fold comes to depend on the person knowing beforehand that it exists. For whoever enters your product a few times a month, that amounts to not existing.
What the brain does with it
The biological mechanism behind the effect, and how much of it was actually measured.
It is a design heuristic — the sixth of Nielsen’s ten, the one that trades remembering for recognising — and not a phenomenon with a mechanism of its own. What supports it is solid: recognising is cheaper than retrieving from memory, and what is off the screen has to be held in the head, in one of the few slots that Miller’s lawGroup into blocks of up to four, and make the blocks contrast with each other.Open the law → counts. The heuristic is the practical consequence of those two things, not an independent finding. Recognising depends on the medial temporal cortexThe inner part of the temporal lobe, hippocampus and surroundings, through which fact and episode pass to become lasting memory. Its role is temporary: over time the memory ends up stored in the cortex and stops depending on this region.See it in Memory →See in the glossary →, as SquireOne reference in this work:1991The medial temporal lobe memory systemSee in the bibliography → and Zola-Morgan reviewed in 1991, and holding what has left the screen depends on working memoryThe mental space where the person holds what they are using right now. It holds about four things, and they fade in seconds if they are not used.See it in Memory →See in the glossary → (Alan BaddeleyFormulated the model of working memory this site uses as its base, the phonological loop, the visuospatial sketchpad and the central executive.One reference in this work:2003Working memory: looking back and looking forwardSee on Wikipedia ↗See in the bibliography →, 2003). Neither of the two measurements was made with an interface in front of anyone, and the link to the heuristic is mine.
The body this law presumes
Who it was measured on, and what changes when the body on the other side is another.
The law says that what is essential stays in view, and a hidden menu serves the secondary. That presupposes a screen. For whoever navigates by screen reader the equivalent is document order and region landmarks, and on a small screen the same rule becomes a different sum, because almost nothing fits in view at the same time.
How design translates it
What to do with it on a screen, without turning a finding into a rule.
How to measure this in your product
Every essential function is in view as soon as the person enters the screen; the secondary goes into an expandable menu or gets less contrast. The classic case is the banking app where “transfer” is on the first screen and “reissue payment slip” is two taps away: the hierarchy says what most people came to do, and what was put away still exists for whoever looks for it. The mistake is the reverse, the everyday function behind an icon the person has to know beforehand exists.
Where it breaks
Where the law does not hold, holds less, or holds in reverse.
Making everything visible is the other way of hiding: when nothing is put away in a menu, the person sweeps the whole screen to find a function, and goes back to paying the cost of searching.
Um caso
A real product where this showed up, with what happened and where to check it.
The hidden menu nobody opened
In 2016 Jakob Nielsen’s group measured, with 179 people on six real sites, what happens when navigation sits behind the three-line icon. On desktop, hidden navigation was used in 27% of tasks, against 48% when it was visible. On mobile, 57% against 86%. Content discovery fell by more than 20% on both platforms, and tasks were at least 39% slower on desktop. The same sections existed in both designs, and what changed was being in view. In the same year Spotify replaced the hidden menu with five fixed tabs at the bottom of the app, and told TechCrunch that clicks on menu items rose 30% and clicks in general rose 9%. The law has a cost on the other side: in 2007 Office replaced the menus with the Ribbon, put everything in view and forced whoever already knew where things were to relearn the programme.
Experimente
A piece to check in your own body what the text has just claimed.
Count the clicks until you reach “Export”
Two bars with exactly the same five functions. Find “Export” in each one and compare the score.
The difference looks small because the bar has five items. It stops being small when the hidden function is the one the person uses every day, or when it is the one they need to find under pressure — cancel, undo, exit. What goes behind “more actions” is a decision about what you think nobody will look for in a hurry.
Neighbouring concepts
Structures linked by a bridge of my own
Sibling concepts
Fontes
Enunciado formulated from Nielsen’s heuristic 6, 1994.
- NIELSEN, J. 10 usability heuristics for user interface design. Nielsen Norman Group, 1994. Source
Leitura complementar: Memory Recognition and Recall in User Interfaces NN/g em inglês