Response Time

Three times, one chain

A performer in a game does not react instantly. Between the moment the stimulus appears and the moment the movement finishes, three separate things happen in order, and Cambridge gives each of them its own name.

Reaction time is the time from the presentation of a stimulus to the start of the movement. It covers the sensing, perceiving, deciding and initiating, and nothing else.

Movement time is the time from the start of the movement to the completion of the movement. It is how long the action itself takes once it has begun.

Response time is the total of the two: the whole process from stimulus to the end of the movement.

The equation that links them

The syllabus asks you to state and use the equation, so learn it as a formula you can rearrange, not a sentence you can recite.

reaction time + movement time → response time

Rearrange it and you can find any one of the three: response time − reaction time → movement time, and response time − movement time → reaction time.

The relationship works because the two parts happen in sequence. A performer's response time is therefore always longer than their reaction time and always longer than their movement time, never shorter.

• Sprinter, gun to first push → reaction time
• Sprinter, first push to end of the drive → movement time
• Sprinter, gun to end of the drive → response time

Simple and choice reaction time: the number of stimuli

Reaction time is not fixed. It depends on how many stimuli the performer has to deal with and how many responses are available. Cambridge names the two extremes.

In simple reaction time there is one stimulus and one known response. The performer knows exactly what is coming and does not have to decide anything. This is the fastest kind of reaction time and it is what a sprinter uses in the blocks: one stimulus, one response, no decision.

In choice reaction time there is more than one possible stimulus and more than one possible response, so the performer must perceive, decide, and then act. Every extra option adds decision time, so choice reaction time is always slower than simple reaction time.

Hick's law

Hick's law (also called the Hick–Hyman law) describes what happens to reaction time as the number of choices increases. Reaction time increases as the number of stimulus–response alternatives increases.

The increase is not straight-line with the number of options. Reaction time rises in step with the logarithm of the number of alternatives, which means each time the number of choices doubles, reaction time goes up by roughly the same extra amount. Two options cost more than one; four options cost more than two; eight options cost more than four, by a similar amount each time.

In practice the message for a performer is simple: the more options a player has to weigh up, the slower their reaction. This is why coaches of novice players reduce the number of options early on, and why an experienced performer who can narrow the choices down quickly reacts faster.

• One choice: quickest reaction time (simple reaction time)
• Two choices: slower, and the performer must discard one option
• Four or more choices: slower again, and the size of the penalty for each doubling of options gets large in real game time
• Application: a beginner netball player who does not know where to pass takes longer to release the ball, so the defender closes the space

The single-channel hypothesis and the psychological refractory period

The single-channel hypothesis says that information is processed through one channel at a time, and that a second stimulus cannot be processed until the first one has been processed. The channel is single, so the processing of the second stimulus has to wait its turn.

The psychological refractory period (PRP) is the brief delay that follows this. It is the period of time during which a performer is still processing the first stimulus and cannot yet fully respond to a second one. Their reaction to the second stimulus is slower than it would normally be.

This matters in sport because a defender or a batter can be made to wait. If an opponent shows one action and then produces a different one shortly afterwards, the defender starts to respond to the first, and by the time the second appears their processing channel is still busy. Their reaction to the real action is delayed.

Deceiving opponents: anticipation and disguise

Because reaction time costs a defender valuable time, skilled performers in attacking positions try to make the defender's reaction as slow and as wrong as possible. There are two sides to this, and a good answer covers both.

Anticipation is where a defender reads the situation early and starts to respond before the stimulus actually happens. It shortens their effective reaction time, but it is a gamble. If they anticipate a pass to the left and the ball goes right, they are committed in the wrong direction and cannot recover in time.

Attackers exploit this deliberately. They use disguise (concealing the real action until the last possible moment, for example a body shape or arm position that hides where the ball is going) and deception (showing a fake action first, then doing something different). A fake forces the defender to start processing the first stimulus, which triggers the psychological refractory period; when the real action follows immediately, the defender's response is delayed and they are beaten.

• Disguise the intended action so the defender has nothing to read
• Fake to one side, then go the other, to exploit the psychological refractory period
• Change the pace or direction late so the defender's anticipation becomes a disadvantage
• Use a defender's anticipation against them: encourage the early move, then punish it

Why a short response time wins matches, and how to get one

A shorter response time gives a performer more time in the remaining phase of play. It is not the whole of skilled performance, but it buys the time that everything else depends on.

A performer with a short response time can begin their movement earlier, so they are already accelerating, already in position and already in balance while a slower opponent is still deciding. They can beat an opponent to the ball, block a shot before it clears the hand, or adjust to a late bounce or a deflection, because they still have spare time. Under pressure they have room to rethink, which is why they appear calm.

Response time can be improved by training the two components separately and then together.

• Practise in realistic conditions so the stimuli are the ones the performer will actually face: live opponents, noisy courts, real ball speeds
• Reduce the number of options early on, then add them back as the performer becomes accurate, so the choices are learned rather than guessed
• Use varied practice with unpredictable feeds or deliveries so the performer is forced to read the stimulus rather than repeat a routine
• Train anticipation and cue reading: watch the opponent's hips, hips and shoulder position, or the server's racket face, and learn the cues that predict what comes next
• Increase the speed of the stimulus (faster feeds, faster bowling machine, faster serving) so the performer must process information more quickly
• Improve technique so that movement time falls, since response time includes the movement itself
• Develop physical qualities that support fast movement: reaction drills, short sprints, plyometrics and agility work for the legs, plus rest so the nervous system is not fatigued