cognitive psychology
Hick's law vs Miller's law
What's the difference between Hick's law and Miller's law?
Hick's law predicts how decision time rises as choice or uncertainty increases; Miller's law concerns immediate-memory capacity. Neither gives a universal limit for the number of menu items.
Also known as: hicks law vs millers law, miller's law vs hick's law
Prefer to watch?
Watch the recap 0:39
The demo
One control, two laws. Drag the number of items and watch each panel react - Hick's measures how long it takes to choose, Miller's how much you can hold in mind. The same count, two different limits.
Hick's law - time to choose
…
Choosing gets slower with the log of the count - a smooth curve, no hard ceiling.
Miller's law - working memory
…
Holding maxes out around seven chunks, then overflows.
Drag the slider and watch the two laws diverge.
What this demo shows (text version)
A slider sets a number of items from 2 to 12, feeding two panels. The Hick's law panel shows the time to choose one option, which rises with the logarithm of the count - so going from few to many options slows decisions down along a smooth curve that never becomes impossible.
The Miller's law panel shows working-memory load as a meter filling toward about seven chunks; past seven it tips into "over capacity". The same number drives two different limits - speed of choosing versus capacity of holding - which is why the two laws are often confused. Hick's is for problems of choice; Miller's is for problems of memory.
Both laws are about "how many", but they measure different things: Hick's law is about choosing - decision time grows with the number of options - while Miller's law is about holding - working memory keeps only a handful of chunks at once. Reach for Hick's when you're shaping decisions, and Miller's when you're sizing what people must remember.
Drag the count up and watch them part ways: Hick's time climbs in a gentle curve (deciding gets slower, but never impossible), while Miller's memory hits a wall around seven and tips into overload. Same number feeding two quite different limits - which is exactly why people muddle them.
When to reach for which: invoke Hick's law when the problem is choosing - a bloated menu, a wall of options, a checkout with too many paths. Invoke Miller's law when the problem is remembering - a code to carry between screens, a multi-step form, anything that asks people to hold information in their head.
The common myth muddles them into "seven is the magic number of menu items". It isn't: Hick's law has no magic number (the curve is smooth, and grouping beats a hard cap), and Miller's seven is about memory chunks, not how many links a navbar may have. Keep them straight and you'll apply each where it actually bites - see [Hick's law](/entries/hicks-law/) and [Miller's law](/entries/millers-law/).