Hick's Law
Decision time grows logarithmically with the number of equally likely choices, so the tenth option costs far less than the second.
Definition
Hick's Law (properly the Hick-Hyman Law) describes how long it takes to choose between alternatives. Reaction time rises with the logarithm of the number of options, not linearly: RT = a + b·log₂(n + 1). Doubling the options adds a fixed increment rather than doubling the time.
Established research. Originates in published research and has been replicated. The effect is real. Its size in your product still needs measuring.
On this page
What the research actually measured
William Hick (1952) and Ray Hyman (1953) ran controlled reaction-time experiments. Participants responded to one of n stimuli, each equally likely, with a pre-learned response mapped to each one. Under those conditions reaction time tracked the information content of the stimulus set almost perfectly.
That setup matters. The law describes choosing among options you already know, that are equally probable, and that map one-to-one onto responses. It is a model of decision time under uncertainty, not a model of scanning an unfamiliar menu.
Applying it without breaking the interface
Do
- Reduce options at moments of genuine decision: pricing tiers, primary calls to action, destructive confirmations.
- Set a strong default so the common case is a confirmation rather than a choice.
- Group long lists into labelled categories so the reader makes one coarse decision then one fine one.
- Order options by likelihood when they are not equally probable. The law assumes equal probability, and real interfaces rarely have it.
Do not
- Hide frequently used items behind a submenu just to shorten the visible list.
- Apply it to search, filtering or browsing, where the user is scanning rather than deciding.
- Use it to justify removing functionality that a segment of users depends on. Move it, do not delete it.
- Quote a specific millisecond figure. The constants a and b are task and population specific.
Where it shows up in product work
The strongest practical use is in onboarding, checkout and destructive flows, where a single decision blocks progress and the options are genuinely unfamiliar. Splitting a fourteen-field signup into three short steps does not reduce total work, but it does reduce the number of decisions held in mind at once, which is a cognitive load argument as much as a Hick argument.
The weakest use is navigation. Global navigation is a recognition task supported by labels the user has seen before. Optimise it for scent and grouping rather than raw item count.
In practice
Pricing pages with three tiers
SaaS marketingThree named tiers with one visually recommended default turns a comparison into a confirmation. Adding a fourth tier is usually a business decision, not a UX one, and it measurably slows selection because the tiers stop being distinguishable at a glance.
Remote control redesigns
Consumer hardwareStreaming remotes collapsed forty buttons into around a dozen by moving rare functions on screen. The decision cost of the common case dropped sharply. The rare functions became slower to reach, which was an accepted trade rather than an oversight.
Sources
Where a source establishes something narrower than the popular reading of it, the note says so.
On the rate of gain of information
W. E. Hick, Quarterly Journal of Experimental Psychology, 1952
The original reaction-time experiments establishing the logarithmic relationship.
Stimulus information as a determinant of reaction time
R. Hyman, Journal of Experimental Psychology, 1953
Independent confirmation and generalisation, which is why the effect is properly the Hick-Hyman Law.
Selection from alphabetic and numeric menu trees using a touch screen
T. K. Landauer and D. W. Nachbar, CHI, 1985
Evidence that broad shallow menus outperform deep narrow ones, complicating naive applications of Hick's Law.
Continue from here
Each link says what the connection is, so you can tell a principle from an alternative from a thing people mix this up with.
Applies when you are designing
Why this works
The reasoning this entry rests on.
- Default EffectCognitive bias
- Choice OverloadPsychology
Hick's Law measures decision time. Choice overload describes what happens when the decision is abandoned instead.
- Cognitive LoadPsychology
- Decision FatiguePsychology
Applied through
Where this shows up as a concrete interface decision.
- DropdownComponent
- Radio GroupComponent
- SelectComponent
- ComparisonPattern
- NavigationPattern
Commonly confused with
Close enough to be mixed up, different enough to matter.
- Miller's LawLaw
Hick's is about decision time under choice. Miller's is about holding items in memory, and is routinely misquoted as a limit on menu length.
Related concept
Connected closely enough to change how you apply this.
- Aesthetic and Minimalist DesignHeuristic
- Recognition Over RecallHeuristic
- Tesler's LawLaw
- Occam's RazorPrinciple
- Progressive DisclosurePrinciple