Hick's Law

Hick's Law (more formally, the Hick-Hyman Law) is one of the oldest empirical findings in human-computer interaction. In 1952, William Hick and Ray Hyman measured how long people took to identify which of N lights had turned on, and found a clean mathematical relationship: response time grew with the logarithm of the number of choices, not linearly. Two options feel only slightly slower than one; ten feel meaningfully slower than two; a hundred feel painfully slow. The formula is T = b · log₂(n + 1) — but for design work, the shape of the curve matters more than its constants.

In interfaces, the same effect shows up in every menu, every settings page, every dropdown. A nav bar with 4 items is faster to scan than one with 14. A button group of 'Yes / No' is faster to act on than 'Yes / No / Maybe / Cancel / Later / Never'. The user isn't reading slower — they're paying a real cognitive cost for each option they have to evaluate and rule out.

The law is most cited as a reason to reduce choices, and that's the right instinct for overlong navigation, overpacked toolbars, and settings pages with thirty unrelated knobs in one list. But the law doesn't say 'always show fewer options' — it says decision time grows with options the user has to consider. Grouping, hierarchy, search, sensible defaults, and progressive disclosure all reduce considered choices without removing the options themselves.

Hick's Law also assumes the user actually has to consider each option. It doesn't apply when the user already knows which item they want — picking 'New York' from a list of 50 US states is fast if you know it's 'New York', regardless of list length. It also assumes options are roughly equivalent in cost; if one option is clearly correct (a primary action) and the rest are clearly secondary, the apparent number of choices collapses to one or two.