Reaction Time vs Response Time: What's the Difference?

Reaction time is the delay between a signal and the start of your response. Response time is the whole thing: your reaction time plus the time it takes to complete the movement. In short:

In everyday speech people often use the two words to mean the same thing. In sports science, psychology and road safety, the difference matters.

The three parts explained

Movement time depends on how far you need to move and how precise the movement must be. Fitts's law describes this: longer movements and smaller targets take more time.

Example: braking in a car

Road safety research shows how much the situation changes response time. In a review of driver braking studies, Marc Green estimated:

• About 0.7 to 0.75 seconds to brake when a driver fully expects the signal.
• About 1.25 seconds for a common but unexpected signal, like the brake lights of the car in front.
• About 1.5 seconds for a real surprise, such as something suddenly entering the road.

These are response times: they include noticing the signal, deciding to brake and moving your foot. They are far longer than a click on a reaction test, mostly because the situation is less predictable and the movement is bigger.

Example: online tests

On our reaction time test, you click or tap the moment the screen turns green. The movement is tiny, so the result is close to your pure reaction time, plus the delay of your device. A large lab study measured simple visual reactions at about 213 ms on average with equipment delays removed.

The aim test is different. Each target appears in a new place, so every result includes a real mouse or finger movement. That makes it closer to a response time test for aiming.

Example: gaming

In a shooter, your response time is everything from an enemy appearing to your shot landing: spotting them, starting to move, and the flick onto the target. You can shorten it in two ways:

• Faster reactions: be rested and focused. See how to improve reaction time.
• Shorter movements: good crosshair placement means less distance to cover. See how to improve your aim.

Other meanings of "response time"

• Monitor response time: how quickly a screen's pixels change colour, in milliseconds. It isn't your reaction time, and it's different from input lag.
• Website or server response time: how long a computer system takes to reply to a request.
• Customer service response time: how long a business takes to reply to a message.

If you came here to test your own speed, take the reaction time test, then read what is reaction time to understand what your result means.