Three kinds of reaction task
The choice mode on this site is a recognition task in the strict sense: some signals say tap and some say hold. It is the cleanest version to measure in a browser, because a wrong response is unambiguous.
- Simple reaction. One signal, one response. The panel turns green, you tap. Around 250 ms for an adult on a screen.
- Recognition reaction. Several signals, but you respond to only one of them. The extra work is deciding whether this is the one.
- Choice reaction. Several signals, each with its own response. You must identify the signal and select the matching action, which costs the most.
Hick's law: the cost of options
In 1952 W. E. Hick showed that reaction time increases with the logarithm of the number of equally likely alternatives, a result Ray Hyman confirmed independently the following year. In plain terms: going from one option to two costs a lot, two to four costs the same again, four to eight costs the same again. Each doubling adds a roughly constant amount, not a proportional one.
The practical effect is that the first decision is expensive and additional options are cheap. Cutting a menu from eight items to six barely helps. Cutting it from two to one removes a decision entirely, and that is where the time is.
The law assumes the options are equally likely and equally easy to tell apart. Make one option much more likely and people effectively stop choosing, which is why familiar tasks feel instant.
What it costs you in practice
| Task | Extra time |
|---|---|
| Recognition — respond to one signal, ignore another | +50 to 100 ms |
| Two-choice — two signals, two responses | +100 to 150 ms |
| Four-choice | +150 to 250 ms |
| Unfamiliar signal-to-response mapping | add another 50 to 200 ms until it is learned |
Why this is the trainable part
Simple reaction time barely responds to practice. Choice reaction time responds a great deal, because what improves is the familiarity of the mapping between a signal and its response. A new driver deliberates over which pedal; an experienced one does not. A new player thinks about which key; a veteran does not.
That is the whole of what people mean by experience making someone "faster". Their nerves are unchanged. Their decisions have become automatic, and the 100 to 200 ms that the decision used to cost has quietly disappeared.