PIXEL REFLEX
REACTION TIME GUIDE EN

QUICK DEFINITION

SIMPLE VS CHOICE REACTION TIME

Simple reaction time measures how fast you make one known response to one expected signal. Choice reaction time adds a decision: identify which signal appeared, then select its matching response.

Choice responses are usually slower because the task includes stimulus identification and response selection—not because the movement itself must be slower.

SIDE-BY-SIDE

The difference is the number of possible stimulus–response mappings

Both tasks measure the interval from a signal to a response. A simple task lets you prepare the response in advance; a choice task requires you to use the current signal to decide which prepared response is correct.

FACTOR SIMPLE REACTION TIME CHOICE REACTION TIME
Rule Detect the signal and make the one known response. Identify the signal and select its assigned response.
Example Press Space when the screen turns green. Press A for a left arrow and L for a right arrow.
Alternatives One response is valid whenever the signal appears. Two or more responses are possible before the signal appears.
Primary result Latency for valid responses, plus false starts. Latency for correct responses, plus accuracy and error types.
Especially sensitive to Cue detection, readiness, anticipation, and input delay. All simple-task factors, plus mapping, compatibility, uncertainty, and accuracy strategy.

STIMULUS → RESPONSE

Choice reaction time depends on the map you must follow

A stimulus–response mapping is the rule connecting each possible cue to an action. The clearest browser example is spatial: a left arrow maps to the left key and a right arrow maps to the right key.

Compatible mappings feel natural and are easier to learn. Arbitrary or conflicting mappings—such as pressing right for a left-pointing arrow—can add selection difficulty even when the number of choices stays the same.

Try the Choice Reaction Test
SIMPLE

Start-light response

One light appears. Press the same key every time.

2-CHOICE

Direction match

A left or right arrow appears. Press its matching key.

GO / NO-GO

Respond or withhold

Press for a green cue, but make no response to a red cue.

RT a b · log₂(N)

WHY MORE CHOICES TAKE TIME

The Hick–Hyman law describes a logarithmic pattern

In classic choice-reaction experiments, average response time tended to increase roughly with the logarithm of the number of possible stimulus–response alternatives. Doubling an equally likely set adds one bit of uncertainty, rather than simply doubling reaction time.

One common equal-probability form is RT = a + b · log₂(N). Here, N is the number of alternatives; a and b are fitted for a particular task and group. Hick's original form used log(N + 1) to include a no-signal state, and Hyman showed that actual signal probabilities and recent sequence information matter. The formula is therefore a model of defined conditions, not just a count of buttons.

DO NOT TREAT IT AS A UNIVERSAL TIMER. The pattern and fitted values change with practice, stimulus–response compatibility, discriminability, errors, and the tested choice range. It predicts task averages under defined conditions, not an exact delay for every person or trial.

FAIR COMPARISON

Keep everything except the decision demand as similar as possible

A browser test is useful for comparing tasks on one setup. It is not a clinical assessment, and scores from different sites or devices may include different display, audio, input, and software delays.

  1. 01

    Match the setup

    Use the same device, browser, screen, input method, posture, and hand. Close distractions and keep the page in focus.

  2. 02

    Match the cues

    Use equally visible signals, the same random wait range, and similar key locations. Avoid making one condition easier to see.

  3. 03

    Learn the mapping

    Practice each response rule before recording. Confusion during early trials measures rule learning as well as reaction.

  4. 04

    Use repeated trials

    Compare equal-size blocks and switch which task comes first. A single fastest response is too sensitive to anticipation and chance.

READ THE RESULTS

Speed and accuracy belong together

Median correct RT
A useful typical score that is less pulled by a few very slow trials.
Accuracy
The share of choice trials answered with the correct mapped response.
Errors
Track wrong choices, missed signals, and responses made before the cue separately.
Consistency
The spread across trials shows whether a typical result is stable or highly variable.

WHICH TEST SHOULD YOU USE?

Choose the task that matches the question

Use a simple test for detection and initiation

It is useful when you want one clear cue and one prepared action: a start signal, a basic alertness check, or a same-device comparison of cue types.

Use a choice test for selection under a rule

It is useful when the task involves identifying a cue and choosing an action: direction matching, color–key rules, game controls, or interface alternatives.

Use go/no-go for response versus restraint

A go/no-go task asks for one action to a target and no action to another cue. It is related to choice tasks, but withholding is not the same as choosing between two key presses.

Try the Go / No-Go Test

QUICK QUESTIONS

Simple vs choice reaction time FAQ

What is the main difference between simple and choice reaction time?

A simple task has one expected signal and one known response. A choice task has multiple possible signals, and each signal maps to a particular response. The choice task therefore includes identifying the signal and selecting the correct action.

What are examples of choice reaction time?

Pressing a left or right key for matching arrows, pressing different keys for different colors, choosing a brake or steering response to a road event, and selecting a game action from an on-screen cue are choice reaction examples.

Why is choice reaction time usually longer?

Before moving, you must identify which stimulus occurred and select its mapped response. More uncertainty, an unfamiliar mapping, or incompatible cue and key positions can lengthen this selection stage.

Does twice as many choices mean twice the reaction time?

No. Under the classic Hick–Hyman conditions, average reaction time rises approximately with the logarithm of the number of equally likely alternatives. The exact relationship depends on the task and must be fitted from data.

Should I compare only my fastest score?

No. A fastest trial may reflect anticipation or luck. Compare a typical correct response, such as the median, alongside accuracy, false starts, wrong choices, and trial-to-trial consistency.

SOURCES

Research behind this guide