Reaction Time

About the Reaction Time exercise

Catching a cup as it tips, stepping back at the curb when a car turns, picking up the phone on the second ring: the day is full of moments that ask for a quick, steady reaction, and some that ask for holding one back. Those moments can feel slower or less sure with age, with tiredness or after an illness, and calm practice keeps them familiar.

Reaction Time is a free practice version of the three reactions Franciscus Donders timed in 1868. Simple: tap when the circle appears. Choice: tap the button with the same shape, or the box the circle appears in. Go/no-go: tap for the circle and hold back for the square. A random wait comes before every shape, eight practice shapes come first, the whole board is the button, and the round ends with the typical time, the middle half of the times and a plain picture of every tap.

Donders and the three reactions

In 1868 the Dutch physiologist and eye doctor Franciscus Donders published a simple idea: time how fast someone answers a signal, then add one small thinking step and time it again. The difference is how long that step takes.

He called his three versions methods a, b and c. In the first, a listener repeated a syllable they knew was coming. In the second, any of five syllables could come, and the listener repeated whichever one was called. In the third, the listener answered only one syllable and stayed silent for the rest. On one evening his own times were about 0.20, 0.28 and 0.24 seconds, so recognizing the sound and choosing the reply each took a few hundredths of a second.

Others soon pointed out that deciding whether to answer at all is itself a choice, so the subtraction is not as clean as it looks. The three reactions lasted all the same, and this exercise uses them as Simple, Choice and Go/no-go.

What Reaction Time practices

Noticing and starting

Seeing a signal and starting the movement right away. Simple rounds practice this on its own, with nothing to choose and nothing to hold back.

Choosing between responses

In Choice the shape decides the answer. Each extra button adds a little time, which is why three and four buttons are a graded step.

Holding back

In Go/no-go the circle comes far more often than the square, so tapping becomes a habit, and the square asks the person to stop a tap that is already on its way.

Keeping a steady pace

The wait changes every time, so attention stays on the board between shapes. The picture of the times shows whether the round stayed steady from start to finish.

How the tool works and what it records

Three modes and three free presets: Simple with 20 circles, Choice with 2 buttons and 24 shapes, and Go/no-go with 1 square in 4 and 24 shapes. Choice can be done two ways, matching the shape to its button or tapping the box the circle appears in. The way of doing Choice, the hand used, sound and large print are free at any setting. Pro adds the grading dials: round length (12 to 40 shapes), shorter or longer waits, three or four buttons or boxes, how often to hold back (from 1 in 5 to 1 in 2), shape size and showing each time after a tap. Every round starts with 8 practice shapes that do not count, and Practice again is always offered.

A shape appears after a random wait of 1 to 3 seconds on the steady setting. A tap before it appears, or within a tenth of a second of it, counts as an early tap, and the same shape comes again after a new wait. In Simple and Choice a shape stays up to 5 seconds; in Go/no-go both shapes stay up to 2 seconds. The results show the typical time (the median, the middle of the times), the middle half of the times, early taps, missed shapes and, in Choice and Go/no-go, how many matched or were held back, with a picture of every shape in order. A free account gives 5 rounds a day on the presets and one round a day with every dial; Pro adds every dial, unlimited rounds, a PDF round record, the session log and home practice links.

The go/no-go task

A go/no-go task shows one of two signals at a time: the go signal asks for a tap, and the no-go signal asks for none. It comes straight from Donders' third method, where the listener answered one syllable and stayed silent for the others.

The square is rarer than the circle on purpose. When most shapes ask for a tap, tapping becomes a habit, and holding back for the square means stopping a tap that is already on its way. That moment of holding back is the point of the task. Even in 1868 Donders found that some people answered where they should have stayed silent, so a tap for the square is simply counted.

Screen or paper?

A reaction time needs a screen and a clock: only a screen can show a shape at an unpredictable moment and time the tap to the hundredth of a second. On paper, the nearest practice is the symbol digit sheets, where symbols are matched to a key at a steady pace and timed with a watch.

The printable version is the Symbol Digit Modalities worksheet set on rehabworksheets.com, and there is a free symbol digit worksheet to try first, with no email required.

Using it well

• Start with Simple. Run a Simple round on the steady setting first. It has nothing to choose and nothing to hold back, so it shows how the reaction itself feels before anything is added.
• Keep the setup the same. Times include a delay from the device, which differs between phones, tablets and computers. To compare rounds, use the same device, the same way of responding and the same settings; the list of earlier rounds on this device does exactly that.
• Keep rounds short. Two or three short rounds with a break between them work better than one long one. Stop while it still goes well.
• Let the person begin. Nothing starts on its own: the person presses Begin practice, then Start the round. Sit beside them, point to the middle of the board, and let them choose the moment.
• Use whichever hand is comfortable. Note the hand under Hand used to compare rounds hand by hand. Show each time is off by default; turn it on only if seeing the number helps rather than pressures.

Common questions