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.
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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.
Mean RT for 4 choices is typically 400–600 ms. Above 700 ms suggests you can speed up; below 350 ms is excellent.
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.
Because keyboard choice counts are limited. We could add more, but the cognitive demand gets dominated by motor mapping rather than choice complexity.