Guide · Reaction basics

What Is Reaction Time?

Learn the definition, compare task types and understand what a cue-to-click score includes.

Reaction time is the interval between a stimulus appearing and the response specified by a task. The stimulus is your cue, such as a light or sound. The response might be the start of a movement or a recorded button press. This follows the APA Dictionary of Psychology definition.

From seeing a signal to starting an action

1Notice the signalYou see a light or a change on the screen.
2Recognize and decideYou identify the cue and apply the response rule.
3Initiate the actionYou begin the instructed movement, such as pressing a button.

A simplified explanation of a voluntary response. These are conceptual steps, not three separately measured timers.

In a laboratory, timing may stop when movement begins. A browser usually stops when it receives the click or key event, which can include some movement and device delay. Always check the endpoint. Intervals are normally expressed in milliseconds (ms).

Simple, choice and go/no-go: three different tasks

Task	What you decide	Example
Simple reaction time	The action is already known. Respond when the cue appears.	Press the same button whenever the panel turns green.
Choice reaction time	Choose which response matches the cue.	Press left for a circle and right for a square.
Go/no-go	Decide whether to respond at all.	Press for a circle; withhold the press for a square.

Choice and go/no-go tasks also require checking wrong responses or missed cues. Speed alone does not describe their performance. AimTests currently offers the simple visual task; the other rows explain concepts rather than selectable test modes.

Reaction time, movement time and reflex

Term	Meaning	Example
Reaction time	The delay from a cue to the response defined in the task.	A signal appears, then your instructed response begins.
Movement time	The time spent carrying out a movement after it starts.	Your hand travels from its starting position to a button.
Reflex	An automatic response that does not require conscious effort.	Your pupil changes size in response to light.

The reflex definition and pupil example come from the APA Dictionary. A deliberate click after a cue is not a clinical reflex examination.

Response time is sometimes a synonym for reaction time. In other contexts, it includes completing the movement. Anticipation means acting on a prediction of when the cue will arrive; a quick guess does not necessarily show a quick response to the signal.

Examples in everyday life and games

A notification sound: noticing the sound and starting to reach for your phone illustrates an auditory cue followed by an action. The reach adds movement time.
A color-change drill: seeing green and pressing a known button illustrates a simple visual response. A touchscreen tap is still a response to a visual cue.
Recognizing a teammate: deciding to withhold a shot resembles the response rule in a go/no-go task, although an actual game involves much more information.
Selecting an ability: choosing different keys for different situations resembles a choice task. Moving the crosshair and aiming add further demands.

Visual, auditory and tactile describe the cue: seeing, hearing or feeling it. They do not specify whether the task is simple or involves a choice. Scores from those different tasks cannot be converted by subtracting a fixed number of milliseconds.

Connect the concept to a measurement

A browser reading includes the screen and input path as well as your response. That brief limitation matters when interpreting the concept; equipment calibration and published values are covered in the Average data reference. For organized practice, use Reaction Time Training.

Definition sources

American Psychological Association. Reaction time, APA Dictionary of Psychology.
American Psychological Association. Reflex, APA Dictionary of Psychology.

Frequently asked

What is reaction time in simple terms?

It is the interval between a cue appearing and the response specified by the task. The cue might be a light or sound; the response might be the start of a movement or a recorded button press.

What unit is used?

Usually milliseconds, written as ms. One millisecond is one thousandth of a second. A task must define which events start and stop its clock.

Is reaction time the same as a reflex?

No. A reflex is an automatic response that does not require conscious effort, such as the pupil changing size in response to light. Pressing a button after a signal follows an instruction, even if the action feels automatic after practice.

How is choice reaction different from a simple response?

In a simple task, the response is known before the cue appears. In a choice task, the cue tells you which response to select. A go/no-go task instead asks you to respond to one cue and withhold a response to another.

Is tapping a screen a tactile task?

Not necessarily. The stimulus determines the sensory label. Seeing a color change and tapping the screen is a visual task. A tactile task would use a touch or vibration as its cue.

Are reaction time and response time interchangeable?

Sometimes. The APA Dictionary lists response time as another name for reaction time. Other tasks use total response time for the interval through completion of an action. Check the stated endpoint before comparing terms.

Experience the simple visual example.

Try the Reaction Time Test