[playful page] A toy, not a test. It runs in your browser; nothing you do here is sent anywhere, and the only thing kept is a "played" tick in your own browser so the toy shelf can show it.

TOY #4 OF 6 works with a mouse, a finger or a keyboard

hen the box turns purple, click it, tap it, or press the space bar, as fast as you can. Part one is five goes where anything counts. In part two the box sometimes turns green instead; leave that one alone.

This toy needs JavaScript. The notes below still say what it would have shown.

What it shows. The time between something happening and your response to it. In 1868 the Dutch physiologist F. C. Donders compared a simple reaction (one signal, one response) with reactions where people first had to tell signals apart, and took the difference as the time needed for the extra mental step (Donders, 1969) [paraphrase, not a quotation]. Part two here is close to his "c" reaction: respond to one signal and not the other. Later work found that choice reaction time grows with the number of alternatives, in proportion to the information involved (Hick, 1952) [paraphrase, not a quotation]. What it cannot show. Your number includes your screen, your mouse or touchscreen, and your browser, all of which add delays of their own. Woods and colleagues found that simple reaction times rise with age and with a shorter wait before the signal, and that computer hardware and software can add delays of their own (Woods et al., 2015) [paraphrase, not a quotation], so do not compare your score with someone else's on a different machine. Donders' subtraction also assumes the extra step just slots in without changing the rest, which later researchers questioned.

Sources

1. Donders (1969). On the speed of mental processes. Acta Psychologica. doi:10.1016/0001-6918(69)90065-1
2. Hick (1952). On the Rate of Gain of Information. Quarterly Journal of Experimental Psychology. doi:10.1080/17470215208416600
3. Woods et al. (2015). Factors influencing the latency of simple reaction time. Frontiers in Human Neuroscience. doi:10.3389/fnhum.2015.00131

see also

	William James — who wrote about reaction-time work in the Principles
	reaction time — in the glossary
	timeline: psychophysics — Donders is on it