Attention
Random Dot Motion Task
Also called: random dot kinematogram, RDK, motion coherence task, dot motion discrimination
Measure the motion coherence threshold and response times with moving dots at six coherence levels, redrawn on every screen frame.
7-9 minTimed: desktop or laptop with a mouse or trackpad
Free to start: 10 free participants per account, then $0.99 per participant for academic research, or any yearly plan. Preview any test free after you sign up.
- Papers, 2021 to 2025
- 291
- Evidence grade
- B
- Registered clinical studies
- 11
What it measures
Measures how much coherent motion a person needs to judge its direction. In a field of moving dots, a share of the dots drifts left or right while the rest move at random. Participants press an arrow key for the direction as soon as they have decided.
Constructs
- Motion perception
- Perceptual decision making
- Visual sensitivity
Research uses
- Perception and decision research
- Within-study group comparison
- Individual differences in motion sensitivity
How the paradigm works
The random dot motion task measures how much coherent motion a person needs to see its direction. A cloud of white dots moves around a red point. On each trial a share of the dots, the motion coherence, moves together to the left or to the right, and the other dots jump to random places. Participants press the left or right arrow key for the direction as soon as they have decided.
More about the paradigm
The display follows Palmer, Huk and Shadlen (2005): white dots of 0.1 degree on black in a 5 degree circle around a 0.4 degree red disk, 16.7 dots per square degree per second, drawn as three interleaved sets so that each coherent dot moves 5 degrees per second. Sizes are set in screen pixels without calibration, at 40 pixels per nominal degree, so the visual angle depends on the screen and the viewing distance. Each trial starts with the red disk alone for 500 to 1000 ms, and the dots move until a response or 3000 ms. Six coherence levels (0, 3.2, 6.4, 12.8, 25.6 and 51.2%) are mixed in one random order, 30 trials each by default, with each direction on half of the trials at every level, after 8 practice trials with feedback. The dots are redrawn on every screen frame at the measured refresh rate, and each trial records its frame timing. Every session runs a recorded random order.
The coherence threshold is the coherence at which a Weibull function fitted to proportion correct by coherence reaches 81.6% correct, the threshold criterion of Britten et al. (1992). Lower values mean weaker motion was enough. Accuracy and median correct response time are also reported at each moving coherence level. At 0% coherence no direction is correct, so that level reports only the median response time.
Scores
- Coherence Threshold%
- Motion coherence at which the fitted Weibull function reaches 81.6% correct.
- Lower means weaker motion was enough
- Psychometric Slopescore
- Slope of the fitted Weibull function.
- Higher means accuracy rose more steeply with coherence
- Lapse Rate%
- Fitted share of errors on displays easy enough to answer correctly.
- Lower means fewer lapses
- Accuracy%
- Share of trials at the moving coherence levels answered with the direction of the moving dots.
- Higher is better
- Median Correct RTms
- Median response time of correct answers at the moving coherence levels, from the onset of the dots.
- Lower is faster
- Accuracy at 3.2%%
- Share correct at 3.2% coherence.
- Higher is better
- Accuracy at 6.4%%
- Share correct at 6.4% coherence.
- Higher is better
- Accuracy at 12.8%%
- Share correct at 12.8% coherence.
- Higher is better
- Accuracy at 25.6%%
- Share correct at 25.6% coherence.
- Higher is better
- Accuracy at 51.2%%
- Share correct at 51.2% coherence.
- Higher is better
- Median RT at 0%ms
- Median response time at 0% coherence, where no direction is correct.
- Lower is faster
- Median Correct RT at 3.2%ms
- Median correct response time at 3.2% coherence.
- Lower is faster
- Median Correct RT at 6.4%ms
- Median correct response time at 6.4% coherence.
- Lower is faster
- Median Correct RT at 12.8%ms
- Median correct response time at 12.8% coherence.
- Lower is faster
- Median Correct RT at 25.6%ms
- Median correct response time at 25.6% coherence.
- Lower is faster
- Median Correct RT at 51.2%ms
- Median correct response time at 51.2% coherence.
- Lower is faster
- Dropped Frame Rate%
- Share of display frames the browser dropped while the dots moved.
- Above 0.05 is flagged for review
Use and evidence
291 papers from 2021 to 2025 name this task in their title or abstract, down 7% compared with 2016 to 2020. That ranks it 87 of 395 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 82 |
| 2024 | 77 |
| 2023 | 51 |
| 2022 | 42 |
| 2021 | 39 |
| 2020 | 53 |
| 2019 | 66 |
| 2018 | 64 |
| 2017 | 59 |
| 2016 | 71 |
| 2015 | 44 |
| 2014 | 77 |
| 2013 | 82 |
| 2012 | 88 |
| 2011 | 78 |
| 2010 | 169 |
| 2009 | 34 |
| 2008 | 30 |
| 2007 | 35 |
| 2006 | 32 |
| 2005 | 36 |
| 2004 | 40 |
| 2003 | 26 |
| 2002 | 25 |
| 2001 | 24 |
| 2000 | 19 |
Use grade C
100 to 299 papers from 2021 to 2025.
Evidence grade B
At least 8 test-retest papers, and either 5 registered clinical studies or 150 reliability or validity papers.
- Papers on test-retest reliability
- 8
- Papers on reliability or validity
- 119
- Registered clinical studies using it as an outcome
- 11
Published reliability
- Test-retest ICC .60 for motion coherence thresholds. (Clark et al. 2022) https://doi.org/10.1167/jov.22.8.18
How the grades work
Use: A is 1,000 or more papers from 2021 to 2025, B 300 to 999, C 100 to 299, D 30 to 99 and E fewer than 30. Evidence: A means at least 25 papers report its test-retest reliability and at least 25 registered clinical studies use it as an outcome; B, at least 8 test-retest papers, and either 5 registered clinical studies or 150 reliability or validity papers; C, at least 2 test-retest papers, 30 reliability or validity papers or 3 registered clinical studies; D, little published measurement evidence found. The counts measure use. They include every paper that names the task in its title or abstract. Grades describe the published research on this task, not ConductCognition's version of it.
Source: ConductCognition test census 0.14.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- Display
- White dots in a 5 degree circle around a red disk on black, 16.7 dots per square degree per second, drawn as three interleaved sets.
- Motion
- A share of the dots, the coherence, moves left or right at 5 degrees per second; the others jump to random places.
- Sizes
- Screen pixels without calibration, 40 pixels per nominal degree, so the visual angle depends on the screen and the viewing distance.
- Fixation
- 500 to 1,000 ms, drawn at random for each trial.
- Dots
- Move until a response or 3,000 ms.
- Keys
- Left and right arrows for the direction of the drift.
- Coherence
- 0, 3.2, 6.4, 12.8, 25.6 and 51.2%, mixed in one random order, each direction on half of the trials at every level.
- Length
- 30 trials per coherence level (10 to 60), with a break after every 60.
- Practice
- 8 trials with feedback at 51.2% and 25.6% coherence.
- Timing
- The dots are redrawn on every screen frame at the measured refresh rate; more than 5% dropped frames is flagged for review.
This version uses the display and coherence levels of Palmer, Huk and Shadlen (2005), with key presses in place of eye movements and a 3,000 ms response limit. The threshold comes from a fitted Weibull function, as in Britten et al. (1992), in place of the staircase of Newsome and Paré (1988).
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: random_dot_motion_test from the scored run, left or right arrow for the direction of the moving dots (chance 50%, each direction on half the trials at every coherence) within 3,000 ms. Below chance invalidates and not above chance is flagged. One key on 90% of answers invalidates when accuracy is not above chance. Missed responses and responses under 100 ms follow the timed-test rule. More than 5% of display frames dropped, or no threshold within the coherence levels tested, is flagged for review.
Why these rules
Accuracy significantly below chance (one-sided exact test, p < .05) cannot come from guessing; it means the response mapping was reversed or the task was not followed (Slick, Sherman and Iverson 1999 treat below-chance forced-choice performance as definite response bias). Chance-level accuracy can be a real result in impaired participants, so it is only flagged. One option on at least 90% of answered trials, when the correct options are balanced and accuracy is not above chance, means the answers did not depend on the items (the task counterpart of long-string responding in surveys; Curran 2016). Missed responses and responses under 100 ms keep the platform's timed-test rule: more than max(3, 25%) missed responses or more than max(2, 20%) responses under 100 ms invalidate, and any is flagged. A response under 100 ms cannot be a reaction to the stimulus. The threshold depends on dots that move a set distance on every screen frame, so a display that drops frames changes the motion, and a threshold above the strongest coherence tested cannot be estimated.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Trials per coherence level | 30 | 10 to 60 |
Yearly plans can change settings within these limits. Free and pay-as-you-go studies use the standard settings.
Need a setting this test does not have?
Devices and languages
- Timed test: participants need a desktop or laptop with a mouse or trackpad. Participant devices
- Languages: English, Spanish, French, German, Italian, Portuguese (Brazil), Chinese (Simplified) and Japanese.
- Available on: Every plan, including the free plan.
- Recruiting online? See the setup guides for Prolific, Sona Systems, CloudResearch Connect and Qualtrics.
Cite and describe
Participants completed the Random Dot Motion Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Newsome and Paré, 1988; Palmer, Huk and Shadlen, 2005), with the standard settings (trials per coherence level: 30). The main score was coherence threshold (motion coherence at which the fitted Weibull function reaches 81.6% correct).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Newsome, W. T., & Paré, E. B. (1988). A selective impairment of motion perception following lesions of the middle temporal visual area (MT). Journal of Neuroscience, 8(6), 2201-2211. https://doi.org/10.1523/JNEUROSCI.08-06-02201.1988
- Palmer, J., Huk, A. C., & Shadlen, M. N. (2005). The effect of stimulus strength on the speed and accuracy of a perceptual decision. Journal of Vision, 5(5), 376-404. https://doi.org/10.1167/5.5.1Display, coherence levels and response-time procedure.
- Britten, K. H., Shadlen, M. N., Newsome, W. T., & Movshon, J. A. (1992). The analysis of visual motion: A comparison of neuronal and psychophysical performance. Journal of Neuroscience, 12(12), 4745-4765. https://doi.org/10.1523/JNEUROSCI.12-12-04745.1992Weibull function and the 82% threshold criterion.
Source papers
- Newsome WT, Paré EB (1988). A selective impairment of motion perception following lesions of the middle temporal visual area (MT). Journal of Neuroscience, 8(6):2201-2211.Paradigm source, Monkeys
- Palmer J, Huk AC, Shadlen MN (2005). The effect of stimulus strength on the speed and accuracy of a perceptual decision. Journal of Vision, 5(5):376-404.Paradigm source, Adults
- Britten KH, Shadlen MN, Newsome WT, Movshon JA (1992). The analysis of visual motion: a comparison of neuronal and psychophysical performance. Journal of Neuroscience, 12(12):4745-4765.Paradigm source, Monkeys
Questions
How long does the Random Dot Motion Task take?
About 7 to 9 minutes, as listed in the test library.
What device does a participant need?
Timed test: participants need a desktop or laptop with a mouse or trackpad. The browser must be Chrome, Edge, Firefox or Safari.
What scores does it produce?
Coherence Threshold, Psychometric Slope, Lapse Rate, Accuracy, Median Correct RT, Accuracy at 3.2%, Accuracy at 6.4%, Accuracy at 12.8%, Accuracy at 25.6%, Accuracy at 51.2%, Median RT at 0%, Median Correct RT at 3.2%, Median Correct RT at 6.4%, Median Correct RT at 12.8%, Median Correct RT at 25.6%, Median Correct RT at 51.2% and Dropped Frame Rate. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Random Dot Motion Task used in research?
291 papers from 2021 to 2025 name it in their title or abstract, down 7% compared with 2016 to 2020. That ranks it 87 of 395 test families in the ConductCognition test census (use grade C). Source: ConductCognition test census 0.14.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Random Dot Motion Task have?
In the published research, 8 papers report its test-retest reliability and 11 registered clinical studies use it as an outcome (evidence grade B in the ConductCognition test census). Test-retest ICC .60 for motion coherence thresholds. (Clark et al. 2022)
Which settings can a researcher change?
Trials per coherence level (10 to 60). Settings can be changed on yearly plans; free and pay-as-you-go studies use the standard settings.
Which languages can participants use?
Participants can take this test in English, Spanish, French, German, Italian, Portuguese (Brazil), Chinese (Simplified) and Japanese. English is on every plan, and the other languages come with yearly plans. Have a native speaker read the machine-translated text before launch.
Is this a clinical test?
No. ConductCognition is for research use only. It runs, scores and exports the test; clinical interpretation is outside the platform.
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