When a shape lights up, press its matching key as fast as you can.
01
Choice reaction time measures how quickly you can identify a stimulus and choose the correct response, rather than just reacting to a single signal. Your brain has to do two things at once: recognise which stimulus appeared, and pick the matching response. That extra decision-making step is almost always slower than a simple reaction, often by 100ms or more.
02
In 1952, psychologist William Edmund Hick showed that reaction time increases as a logarithmic function of the number of choices. Double the options and your reaction time goes up by a roughly fixed amount, about 150ms per "bit" of information. This relationship, known as Hick's Law, has been confirmed in hundreds of studies since. A 2018 review by Proctor and Schneider in the Quarterly Journal of Experimental Psychology summarised the evidence: with four choices, most people average around 350ms.
The relationship is logarithmic, not linear: going from 2 to 4 choices adds more time than going from 4 to 8. Practice also makes a big difference: in one study, the gap between 2-choice and 8-choice reaction times shrank from 500ms to 300ms after just five sessions.
03
Choice reaction time is closer to real-world decision making than a simple reaction test. Driving, sports, and gaming all require you to recognise a situation and pick the right response under time pressure. A goalkeeper facing a penalty kick, a driver deciding whether to brake or swerve, a gamer choosing which ability to use: all of these are choice reaction tasks.
Research in cognitive neuroscience shows that the brain handles more alternatives by activating larger networks in the prefrontal cortex. The more options you have, the more neural resources you need to pick the right one. Training and familiarity with the task can reduce this overhead significantly.
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