Demonstrated experimentally by William Hick and Ray Hyman in 1952. Decision time scales with the logarithm of the number of choices — doubling options doesn't double the time, but it does measurably increase it.
In practice, designers don't just delete options; they **group them into categories and split decisions into steps**. Twelve items on one screen become 3 categories × 4 items, and each individual decision speeds back up.
A has 2 choices, B has 12. Compare how long the cursor takes to settle on one (the bar).
When to use
Use this when deciding how many options a dropdown, filter, or onboarding step should show. If you can't cut options, group them (see progressive-disclosure).