Reaction times

23 measured reaction and reflex times, each labelled as one of three things that normally get printed in the same column: a reflex, which turns round in the spinal cord in about 20 milliseconds and never reaches the brain; a reaction, which is a decision and takes about 250; and a design value, which is not a measurement of anyone at all.

• A reflex is not a reaction Why one is 20 ms and the other 250, and why training does not close the gap
• Stopping distance at every speed Reaction distance plus braking distance, on four surfaces, with the maths shown
• Measure your own reaction time Five attempts, median reported, entirely in your browser

Everything, fastest first

If an event gives you less than about 150 milliseconds, reacting is not available and only anticipation is. That is the line that separates the sport entries below into the ones you can respond to and the ones you have to predict.

The basic senses

• Simple tactile reaction time 155 ms — Respond as soon as the skin is touched or vibrated.
• Simple auditory reaction time 170 ms — Press a button as soon as a tone sounds.
• Simple visual reaction time 250 ms — Press a button as soon as a light appears. One stimulus, one response, no choice to make.
• Recognition reaction time 340 ms — Respond to some stimuli and withhold on others — a go/no-go task.
• Choice reaction time 380 ms — Two or more stimuli, each with its own response. Press left for a red light, right for a green one.
• All 5 in the basic senses

Reflexes

• Vestibulo-ocular reflex 10 ms — Head turns; time until the eyes counter-rotate to hold the image still.
• Knee-jerk (patellar) reflex 22 ms — Tap the patellar tendon; time to the quadriceps contracting.
• Blink reflex 40 ms — Air puff or loud sound; time to the eyelid muscle firing.
• Withdrawal reflex 90 ms — Touching something painfully hot or sharp; time to the limb starting to move away.

Driving

• Driver reaction to an expected event 850 ms — Alert driver, anticipating the need to brake; time from stimulus to the brake pedal moving.
• Driver reaction to a surprise 1.35 s — Unanticipated hazard — a car pulling out, an obstacle appearing; time to the brake pedal.
• The 2.5-second road design figure 2.50 s — The perception-reaction time assumed when calculating stopping sight distance for road geometry.

Sport

• Time a jab takes to land 110 ms — Time from the punch starting to contact, at close range.
• Sprint start reaction 140 ms — Time from the gun to measurable force change in the starting blocks.
• Formula One start reaction 200 ms — Time from the five red lights going out to the car moving.
• Time to hit a 95 mph fastball 400 ms — Flight time from the pitcher's release to the plate, about 55 feet at 95 mph.
• Time a goalkeeper has on a penalty 450 ms — Ball flight time from 12 yards at a typical struck-penalty speed.
• Time to play a 90 mph delivery 500 ms — Ball flight from release to the batter over roughly 18 metres of effective distance.
• All 6 in sport

Screens and input

• Latency added by your screen and mouse 35 ms — End-to-end delay between a frame being drawn and an input being registered by software.
• Professional gamer reaction time 190 ms — Simple visual reaction in a game context, on low-latency hardware.

How it varies between people

• How reaction time changes with age 250 ms — Simple visual reaction across the lifespan, from childhood to old age.
• What sleep loss does to reaction time 300 ms — Simple visual reaction after extended wakefulness or restricted sleep.
• What alcohol does to reaction time 320 ms — Simple and choice reaction at blood alcohol concentrations around the common legal driving limits.