Mind Forge All tools
Reaction time

4-Choice Reaction Time (Hick's Law)

An arrow appears in one of four directions. Press the matching arrow key. We log per-choice histograms and estimate your Hick rate constant.

What makes this one different

Hick's law predicts RT = a + b × log2(n). We vary the number of choices and fit your personal slope (the b). Most adults are in the 100–150 ms/doubling range.

Choices
Trial 0 / 40
Mean RT —
·

Press ← ↑ ↓ →

Ad slot.

RT distribution

History

No sessions yet.

What problem does it solve?

Hick's law is one of the foundational laws of human factors: reaction time scales logarithmically with the number of choices. Each doubling of choices adds a roughly constant cost. The slope of this line (Hick rate constant) varies between individuals and contexts.

Who is this for

How to interpret your results

Mean RT for 4 choices is typically 400–600 ms. Above 700 ms suggests you can speed up; below 350 ms is excellent.

Limitations

  • Keyboard latency varies by device. We can't measure this directly.
  • Practice reduces Hick's slope. Run several sessions to see your plateau.

FAQ

Does 2-choice vs 4-choice really differ?

Yes — by Hick's law, 4 choices should be ~100ms slower than 2 (because log2(4) − log2(2) = 1, times the slope). That's a clean, measurable effect.

Why don't you test 8 or 16 choices?

Because keyboard choice counts are limited. We could add more, but the cognitive demand gets dominated by motor mapping rather than choice complexity.

How do I use 4-Choice Reaction Time (Hick's Law) step by step without mistakes?Follow the order given in the usage section: Press the matching arrow key. Per-choice histograms and Hick's rate constant estimation. The step-by-step part matters less than the unit check that sits inside it. Confirm every unit matches the thing you are actually trying to measure before you press calculate - that single check catches more wrong answers than any other habit, and it costs about ten seconds.
What are the common mistakes when using 4-Choice Reaction Time (Hick's Law)?Most common mistakes come down to four habits: entering 20 when the field expects 0.2 because the field is a percentage; leaving a field blank and accepting the default without checking what it stands for; changing one input and reading a result that was calculated before the change; and quoting the output as an exact figure when the page describes it as a reference estimate. Press calculate again after any edit, and treat the number as a reference point rather than a final answer.
How do I read the result from 4-Choice Reaction Time (Hick's Law)?Read the final figure first, then come back to this section for the conditions behind it: Mean RT for 4 choices is typically 400–600 ms. Above 700 ms suggests you can speed up; below 350 ms is excellent. Keep two things apart: the number itself, which comes from the values you typed, and the assumptions it depends on, which decide whether that number is meaningful. The page sets out what a higher or lower result means for your case, so check that direction as well as the magnitude.
Can I act on the 4-Choice Reaction Time (Hick's Law) result directly?Treat it as one reference sheet before you decide, rather than as the answer itself: Keyboard latency varies by device. We can't measure this directly. Practice reduces Hick's slope. Run several sessions to see your plateau. The output describes a magnitude under the conditions you entered. It does not include what it actually costs to act, what might change while you act, or how the other side behaves. Before you commit, compare the result against reality and note which assumptions do not hold where you are.
What inputs does 4-Choice Reaction Time (Hick's Law) need?The inputs for this tool sit in the form area of the page - fill them in one at a time as prompted. Before you start, check that each one uses the unit you actually measured: mismatched units are the most common source of a wrong answer here.
What should I check before I run 4-Choice Reaction Time (Hick's Law)?Three checks pay for themselves. First, confirm the question you need answered is really inside the scope of this tool rather than a neighbouring one. Second, confirm that the figures you have are drawn from the same source and the same period - mixing monthly and annual numbers, or two different definitions of the same quantity, quietly distorts the result. Third, keep the key inputs written down, so that later you can tell which set of numbers produced a figure you are about to quote.