Reaction time
Measure how long it takes you to respond to a signal, and how much longer it takes when you must first choose which of several responses to make.
Method
Procedure
- There are three short rounds, of 8, 12 and 12 trials.
- Round 1: one circle. Wait until it fills, then respond at once.
- Round 2: two circles; respond to the one that fills. Round 3: four circles.
- A response before the circle fills, or within 100 ms of it, counts as too soon and the trial is repeated.
Responses
- Space
- round 1: respond (or tap anywhere on the screen)
- F, J
- round 2: the left or the right circle
- D, F, J, K
- round 3: circles 1 to 4 from left to right
- Touch
- tap the circle, or the button beneath it
Measures
The reaction time on each trial: the time from the screen update in which the circle fills to your key press or tap. Your result is the median of the correct trials in each round. Comparing the rounds shows how much time choosing between alternatives adds to the time needed to detect the signal and move.
Practice
Six practice trials, three with one circle and three with two, tell you after each trial whether your response was right and how fast it was.
Terms
- Reaction time: The time between the appearance of a signal and the response, here in milliseconds (ms; 1000 ms is one second).
- Simple and choice reaction time: Simple: one signal and one response. Choice: several possible signals, each with its own response.
- Median: The middle value when all values are put in order. An occasional very slow response affects it less than it affects the average.
- Anticipation: A response made too early to be a response to the signal; such responses are not counted.
- Motor cortex: The strip of the frontal lobe that sends the commands for voluntary movements.
Experiment
Responses stay in this browser tab. Nothing is stored or sent, and everything is lost when the page is closed or reloaded.
Results
Interpretation
The three medians show how long a response took with one, two and four possible responses. The round with one circle is usually the fastest, because only detection and movement are needed. By Hick’s law (Hick, 1952), each doubling of the number of alternatives adds a roughly constant amount of time, so four circles should be slower than two. Errors must be considered as well: a fast median obtained with many errors does not indicate better performance.
Limitations
The rounds always come in the same order, so practice or tiredness may add to, or hide, the differences between them. With 8 or 12 trials per round, the medians can change by tens of milliseconds from one run to the next. Keyboards, touch screens and browsers add a delay that differs between devices, so the absolute values are less reliable than the differences between rounds.
The result comes from one person in one session, on a device whose timing and display are not calibrated. It describes this run, not a stable characteristic of the participant, and a second run could differ by chance alone. Research studies test many participants under controlled conditions and report the average with its variability. The experiment is educational; it is not a test of ability or health.
One row per trial: round, number of choices, trial number, the circle that filled (1 = leftmost), the circle you chose, reaction time in ms and outcome (correct, error, no response or too soon). In the file, 1 means yes and 0 means no. The file is created on this device and can be opened in a spreadsheet.
Background
Original findings
Even the simplest response takes a fraction of a second: the eye must detect the signal, the brain must process it and a command must travel to the muscles. When several responses are possible, a decision is added. Hick (1952) found that choice reaction time increases by a roughly constant amount each time the number of equally likely alternatives doubles, a relationship now known as Hick’s law.
Neural basis
The signal is processed first in the visual cortex. Regions of the frontal and parietal lobes then select the response, and the motor cortex sends the command through the spinal cord to the muscles.
References
- Hick, W. E. (1952). On the rate of gain of information. Quarterly Journal of Experimental Psychology, 4(1), 11–26. https://doi.org/10.1080/17470215208416600
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