Hick’s law

In 1952 the British psychologist William Hick sat in front of ten lamps arranged in a ring, with a finger on a key for each, and pressed the key for whichever lamp lit.

He was his own subject. The time he took grew with the logarithm of the number of lamps: each time the number of choices doubled, the time rose by the same amount. A year later the American psychologist Ray Hyman showed it was really about uncertainty. Make some choices more likely than others and people answer faster, exactly as information theory, the mathematics of messages and surprise, predicts. The two names stuck together as the Hick–Hyman law, set out in a 2018 review¹ by Robert Proctor and Darryl Schneider.

The law describes people choosing among clear options they have not practiced. Change either part and it changes.

When the link between signal and response is obvious, it can vanish entirely. In a 1959 study, people felt a vibration under the finger they were meant to press, and eight choices took no longer than two. Practice flattens it too: after thousands of trials, the difference between choosing among eight and choosing among two shrinks to a fraction of what it was.

This experiment, like most menus, also asks you to find the word, and finding is different. Scanning an unfamiliar list takes time in proportion to its length, one item after another, as Andy Cockburn and colleagues² showed in 2007. Hick’s law only takes over once people know where things are, like a regular customer who orders without opening the menu.

Hick’s law is often quoted to argue that every menu should be short. If you’ve been told to trim your list of services for that reason, read on: properly read, it says almost the opposite.

Because the cost grows with the logarithm, each added option costs less than the one before. A 2020 paper³ asking how relevant the law is to design concluded that it “speaks against, not for” the idea that less is better. Splitting one menu into several levels makes people choose, wait and choose again, and broad, shallow menus have long been found faster than narrow, deep ones.

The famous jam study is similar. In 2000, a tasting booth in a California supermarket offered 24 jams on some hours and 6 on others. More people stopped at the big display, but of those who stopped, 3% bought jam, against 30% at the small one. A decade later, a review of 63 studies⁵ found the average effect of too much choice was almost zero. It appears when the options are hard to compare, people are unsure what they want, or time is short.