Picture a goalkeeper facing a penalty, a gamer peeking a corner or a driver at a busy junction. In each case the brain has to pick one action from several. The more options there are, the longer that pick takes.
That simple idea has a name. Hick’s law says reaction time grows with the number of choices, but in a curve, not a straight line. Doubling your options does not double your time.
You can feel it in about a minute. Try the free VoltReflex choice reaction test with 2 choices, then switch to 4 and compare your averages.
Key takeaways
- Hick’s law links decision time to the number of equally likely options.
- Time grows with log2(n + 1), so each doubling of options adds a similar step.
- W. E. Hick described it in 1952 and Ray Hyman extended it in 1953.
- In a large Scottish study, a 4 choice task took about 539 ms at age 30 versus 290 ms for a simple task.
- Practice, clear signals and fewer options all cut decision time.
What Is Hick’s Law?
Hick’s law, also called the Hick-Hyman law, describes how long it takes to choose between options that are equally likely. More options mean more time, but each extra option costs a little less than the one before.
The reason is that your brain does not check every option one by one. It narrows them down, a bit like splitting a list in half again and again until one answer is left.
This is different from Fitts’ law, which covers how long it takes to move to a target. Hick’s law is about deciding. Fitts’ law is about moving. Real tasks usually need both.
The Hick’s Law Formula
A common way to write it is shown below.
T = b × log2(n + 1)
- T is the time it takes to decide.
- n is the number of equally likely choices.
- b is a constant you measure for each person and task.
The plus one accounts for the extra question of whether to respond at all. The log2 part is what makes the curve bend. The table shows how the decision load grows.
| Choices (n) | log2(n + 1) | Load vs 1 choice |
|---|---|---|
| 1 | 1.00 | 1.0x |
| 2 | 1.58 | 1.6x |
| 4 | 2.32 | 2.3x |
| 8 | 3.17 | 3.2x |
| 16 | 4.09 | 4.1x |
Going from 1 to 16 options makes the choice part about four times heavier, not sixteen times. Real reaction times also include a fixed part for seeing and moving, so the total grows even more gently.
Where Hick’s Law Comes From
British psychologist William Edmund Hick published “On the rate of gain of information” in 1952. He used a set of lamps, each matched to its own key, and timed how fast people pressed the right key as the number of possible lamps changed. Reaction time rose with the logarithm of the number of choices.
A year later, Ray Hyman showed that reaction time rose in a straight line with the amount of information in the signal, measured in bits. That is why the rule is often called the Hick-Hyman law.
Both studies came from early information theory, the same maths behind computer bits. One bit is the information in a choice between two equally likely options.
What Real Data Shows
A study of 2,196 adults in Scotland measured simple and 4 choice reaction times with the same device at three ages. The choice task took much longer at every age.
| Age | Simple | 4 choices | Extra time |
|---|---|---|---|
| 30 | 290 ms | 539 ms | +249 ms |
| 50 | 318 ms | 623 ms | +305 ms |
| 69 | 354 ms | 729 ms | +375 ms |
Adding a four way decision almost doubled the time, and the cost grew with age. We cover this study in more detail in choice vs simple reaction time.
Test yourself Run the choice reaction test with 2 choices and 10 rounds, then repeat with 4 choices. Write down both averages. The gap is your own Hick’s law cost.
When Hick’s Law Does Not Fit
Hick’s law is a useful rule of thumb, not a law of nature. It works best when options are equally likely and you know the layout well. Several things can bend it.
- Clear matches. When the signal and response line up naturally, like pressing the key right under a light, the choice cost shrinks. Researchers call this stimulus-response compatibility.
- Practice. Very familiar choices become almost automatic, so the extra time drops.
- Unequal odds. If one option is far more likely, people expect it and react faster to it.
- Unsorted lists. Searching a random list item by item grows in a straight line, not a curve, so Hick’s law does not apply there.
Hick’s Law in Sport, Gaming and Design
In sport, a defender who reads the attacker’s hips cuts the likely options from many to one or two. Fewer options means a faster response. See reaction time by sport.
In gaming, pre-aiming common angles and learning enemy habits does the same job. Simple crosshair placement and a clean key layout reduce the decision load. Our gamer reaction time tips cover this.
In design, Hick’s law is often quoted to argue for short menus and fewer buttons. A 2020 paper by Liu and colleagues argued this is often a misreading, and that visual search and decision making matter more than the law itself for most screen tasks. So treat it as a guide, not a strict rule.
Frequently Asked Questions
What is Hick’s law in simple terms?
What is the Hick’s law formula?
Who discovered Hick’s law?
Where is Hick’s law used?
How can I test Hick’s law myself?
The Bottom Line
Hick’s law explains why decisions cost time. More options slow you down, but each extra option adds a little less. Practice, clear signals and fewer choices all help.
See it for yourself. Take the free choice reaction test with 2 and then 4 choices, and compare it with your simple reaction time test score.
VoltReflex results are for entertainment and self-benchmarking, not a medical diagnosis.
Sources
- Hick (1952), On the rate of gain of information, Quarterly Journal of Experimental Psychology
- Hyman (1953), Stimulus information as a determinant of reaction time, Journal of Experimental Psychology
- Der and Deary (2017), Reaction time and intelligence in cohorts aged 30, 50 and 69 years
- Liu et al. (2020), How Relevant is Hick’s Law for HCI