Attention
Motion Aftereffect Task
Also called: motion after-effect, MAE, waterfall illusion, dynamic motion aftereffect, motion adaptation, MAE nulling
Measure how watching steady motion changes what looks still: people judge which way brief clouds of twinkling dots drift, before and after watching dots drift one way.
9-11 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. Try it here first, with no account.
- Papers, 2021 to 2025
- 58
- Evidence grade
- D
- Registered clinical studies
- 0
What it measures
A measure of how watching steady motion changes what looks still. A cloud of twinkling dots shows for a second, some of them drifting together left or right, and participants press the left or right arrow for the way it drifted. The first part has no adapter; in the second the dots first drift one way for 30 seconds and again before every test. The score is the shift in the share of drifting dots that looks still, compared with the first part.
Constructs
- Motion perception
- Visual adaptation
- Direction-selective adaptation
Research uses
- Visual perception and adaptation research
- Individual differences in perception
- Within-study group comparison
How the paradigm works
The Motion Aftereffect Task measures how watching steady motion changes what looks still. After a person has watched dots drift one way for some seconds, dots that twinkle at random seem to drift the other way, the effect behind the waterfall illusion (Anstis, Verstraten and Mather, 1998). Adding dots that drift the way the adapter drifted cancels the illusion, and the share of drifting dots needed to make the test look still measures the aftereffect (Blake and Hiris, 1993).
More about the paradigm
On a dark panel a red dot stays in the middle of a round window 240 px across. Each test is a cloud of 400 white dots shown for 1 second: on every screen frame some of the dots, a share set by the test's coherence, step together to the left or to the right, and the rest jump to random places. The coherences are 30, 20, 10, 6 and 3% to the left, 0, and 3, 6, 10, 20 and 30% to the right, the levels of Gallagher, Suddendorf and Arnold (2019), each 4 times in each part (standard; 4 to 8), with 4 check tests at 60%. After the cloud has gone, the participant presses the left or right arrow for the way it drifted, with no time limit. The first part has no adapter. In the second, the window first fills for 30 seconds with dots drifting one way at 30% coherence, the way drawn from the session's seed, and again for 5 seconds before every test. That gives 96 tests after 6 practice tests with feedback, about 9 to 11 minutes. Every coherence and display time is set before the session: no answer changes a later trial, and there is no staircase or training mode. Desktop and laptop only.
The main score is the motion aftereffect: the coherence that looks still after the adapter minus the coherence that looks still with no adapter, from a cumulative Gaussian fitted to the answers of each part, in percent of dots drifting the adapter's way. Positive values are the classic effect: after the adapter, dots must drift its way to look still. The still point and the spread of each part are also reported. The dots move at the same speed on any refresh rate and their twinkle follows the screen's own rate; sessions on screens below 50 Hz are flagged. Sizes are CSS pixels, so the dots' size and speed in degrees depend on the screen and the viewing distance: compare groups on similar equipment. Sparse dots can understate the aftereffect (Castet, Keeble and Verstraten, 2002), so values compare within this task, not with laboratory nulling percentages. One person's shift rests on 44 tests a part and is noisy: read it across a group. Answers at the weak coherences are the measure and are never counted as errors; the check tests show whether the keys followed the display. Scores support research and do not diagnose.
Scores
- Motion Aftereffect%
- The coherence that looks still after the adapter minus the coherence that looks still with no adapter, in percent of dots drifting the adapter's way, from a cumulative Gaussian fitted to each part's answers.
- Positive is the usual finding: dots must drift the adapter's way to look still; not better or worse
- Still Point With No Adapter%
- The coherence that looks still in the first part, which has no adapter, positive the way the session's adapter drifts.
- Informational; near 0 for most people
- Still Point After the Adapter%
- The coherence that looks still in the second part, after the adapter, positive the way the adapter drifts.
- Usually above the still point with no adapter
- Spread With No Adapter%
- Half the distance between the coherences answered the adapter's way on 25% and on 75% of tests in the first part, from the fitted curve.
- Smaller means finer judgments of drift
- Spread After the Adapter%
- The same spread in the second part, after the adapter.
- Informational
- Answers the Adapter's Way With No Adapter%
- Share of answers naming the way the session's adapter drifts, at each coherence of the first part, keyed by percent drifting that way (negative: the other way).
- Rises with the coherence
- Answers the Adapter's Way After the Adapter%
- Share of answers naming the adapter's way at each coherence of the second part, keyed the same way.
- Usually lower than with no adapter near 0
- Check Test Accuracy%
- Share of the check tests, with 60% of the dots drifting one way, answered right, when at least 4 were answered.
- Below 0.5 is invalid and below 0.75 is flagged for review
- Median Answer Timems
- Median time from the end of the test to the answer.
- Informational; the answer has no time limit
- Anticipationscount
- Answers under 100 ms from the end of the test, which are not scored.
- Lower is better
- Early Key Pressescount
- Arrow keys pressed before the test ended, which are not taken as answers.
- Informational
- Frame Intervalms
- Median time between screen frames during the trials.
- About 16.7 on a 60 Hz screen
- Refresh RateHz
- Screen frames a second, from the median frame interval.
- Below 50 is flagged for review
- Dropped Frames%
- Share of the frames the browser skipped while the adapter, the blank and the tests were shown.
- Above 0.05 is flagged for review
- Test Durationms
- Median measured time the test dots were on screen.
- About 1,000
- Adapter Timeseconds
- Measured time the drifting adapter was on screen over the second part.
- Informational
- Completed Trialstrials
- Tests answered in the scored run.
- Fewer than planned is flagged for review
- Planned Trialstrials
- Tests the run set out to show.
- Informational
Use and evidence
58 papers from 2021 to 2025 name this task in their title or abstract, down 41% compared with 2016 to 2020. That ranks it 286 of 495 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 19 |
| 2024 | 12 |
| 2023 | 9 |
| 2022 | 6 |
| 2021 | 12 |
| 2020 | 10 |
| 2019 | 21 |
| 2018 | 24 |
| 2017 | 14 |
| 2016 | 30 |
| 2015 | 17 |
| 2014 | 35 |
| 2013 | 27 |
| 2012 | 39 |
| 2011 | 37 |
| 2010 | 120 |
| 2009 | 31 |
| 2008 | 24 |
| 2007 | 26 |
| 2006 | 19 |
| 2005 | 29 |
| 2004 | 36 |
| 2003 | 20 |
| 2002 | 20 |
| 2001 | 20 |
| 2000 | 11 |
Use grade D
30 to 99 papers from 2021 to 2025.
Evidence grade D
Little published measurement evidence found.
- Papers on test-retest reliability
- 0
- Papers on reliability or validity
- 23
- Registered clinical studies using it as an outcome
- 0
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 0.22.0, counted 3 November 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- Display
- A red dot in the middle of a dark panel, and around it a round window 240 px across with 400 white dots. On every screen frame some dots, a share set by the coherence, step together left or right, and the rest jump to random places.
- Test
- A cloud of dots for 1,000 ms, 250 ms after the adapter or the plain panel, at a coherence of 30, 20, 10, 6 or 3% to the left, 0, or 3, 6, 10, 20 or 30% to the right, each 4 times in each part (standard; 4 to 8), and 4 check tests at 60%.
- Adapter
- Dots drifting one way at 30% coherence, the way drawn from the session's seed, for 30 seconds at the start of the second part and 5 seconds before every test.
- Parts
- First a part with no adapter, the red dot alone for 1,000 ms before each test, then the adapting part: 96 tests in all.
- Speed
- 120 px per second, 2 px a frame on a 60 Hz screen: each step is the speed times the time since the last frame, so the speed holds at any refresh rate.
- Answer
- After the cloud has gone, press the left arrow if the dots drifted to the left or the right arrow if they drifted to the right, with no time limit. Keys pressed before the cloud ends are counted and not taken as answers.
- Practice
- 6 tests at 60% coherence with no adapter, with feedback for 1,000 ms.
- Fixed displays
- Every coherence, the adapter and every display time are set before the session, and no answer changes a later trial: there is no staircase and no training mode.
- Score
- The coherence that looks still after the adapter minus the coherence that looks still with no adapter, from a cumulative Gaussian fitted to each part's answers, in percent of dots drifting the adapter's way; positive when dots must drift the adapter's way to look still. Answers under 100 ms leave the score.
The dots keep their speed at any refresh rate, their twinkle follows the screen's own rate, and a screen below 50 Hz is flagged. They are drawn in screen pixels, so their size and speed in degrees of visual angle depend on the screen and the viewing distance: compare groups on similar equipment. One person's shift is noisy, so read the aftereffect across a group. Answers at the weak coherences are never scored as errors.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: motion_aftereffect_test from the scored run, the left arrow when the dots drifted to the left or the right arrow when they drifted to the right, with no time limit. The weak levels, up to 30% of the dots drifting together, are the measure: the adapter makes some of them look as if they drift the other way, so accuracy is not judged on them and no answer to one is ever an error. Only the check tests, with 60% drifting together, have a right answer: with at least 4 answered, under half right invalidates and under three quarters is flagged. Answer times run from the end of the test; responses under 100 ms follow the timed-test rule. No aftereffect, a run short of its planned tests, more than 5% of frames dropped, or a screen under 50 frames a second is flagged for review.
Why these rules
There is no correct option to compare with chance, so accuracy is not judged against chance. After dots drift one way, twinkling dots seem to drift the other way (Blake and Hiris, 1993), so a "wrong" answer at a weak level is the aftereffect itself. A test with 60% of the dots drifting together lies far beyond the shifts the sources report, so wrong answers there mean the keys did not follow the display. The dots are drawn on screen frames, so a display that dropped frames, or ran slower than the dots assume, changed what was shown, and a hidden tab, which stops the adapter, withholds the percentile.
No percentile. Scores and quality flags only.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Tests at each coherence | 4 | 4 to 8 |
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.
- No percentile. Scores and quality flags only. How norms work
- Recruiting online? See the setup guides for Prolific, Sona Systems, CloudResearch Connect and Qualtrics.
Cite and describe
Participants completed the Motion Aftereffect Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Blake and Hiris, 1993), with the standard settings (tests at each coherence: 4). The main score was motion aftereffect (the coherence that looks still after the adapter minus the coherence that looks still with no adapter, in percent of dots drifting the adapter's way, from a cumulative Gaussian fitted to each part's answers).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Anstis, S., Verstraten, F. A. J., & Mather, G. (1998). The motion aftereffect. Trends in Cognitive Sciences, 2(3), 111-117. https://doi.org/10.1016/S1364-6613(98)01142-5The aftereffect after looking at a waterfall, and a test of drifting and randomly twinkling dots in which a just large enough share of dots drifting the adapter's way cancels it.
- Blake, R., & Hiris, E. (1993). Another means for measuring the motion aftereffect. Vision Research, 33(11), 1589-1592. https://doi.org/10.1016/0042-6989(93)90152-MAdaptation to dots moving one way, then tests of dots moving in all directions, cancelled by a share of dots moving the adapter's way and found by the method of constant stimuli.
- Gallagher, R. M., Suddendorf, T., & Arnold, D. H. (2019). Confidence as a diagnostic tool for perceptual aftereffects. Scientific Reports, 9, 7124. https://doi.org/10.1038/s41598-019-43170-1Tests from 30% to the left to 30% to the right for 1 second on a 60 Hz screen, a baseline with no adapter, and an adapter at 30% coherence that moved the still point about 11 percentage points its way.
- Park, M., Blake, R., Kim, Y., & Kim, C.-Y. (2019). Congruent audio-visual stimulation during adaptation modulates the subsequently experienced visual motion aftereffect. Scientific Reports, 9, 19391. https://doi.org/10.1038/s41598-019-54894-550 seconds of adaptation at the start of a block and 5 seconds before each brief test, with the coherence that cancels the aftereffect as its strength.
- Castet, E., Keeble, D. R. T., & Verstraten, F. A. J. (2002). Nulling the motion aftereffect with dynamic random-dot stimuli: Limitations and implications. Journal of Vision, 2(4), 3. https://doi.org/10.1167/2.4.3Tests with few dots underestimate the aftereffect, so values compare within one display, not across displays.
Source papers
- Blake R, Hiris E (1993). Another means for measuring the motion aftereffect. Vision Research, 33(11):1589-1592.Paradigm source, Adults
- Gallagher RM, Suddendorf T, Arnold DH (2019). Confidence as a diagnostic tool for perceptual aftereffects. Scientific Reports, 9:7124.Paradigm source, Adults
Questions
How long does the Motion Aftereffect Task take?
About 9 to 11 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?
Motion Aftereffect, Still Point With No Adapter, Still Point After the Adapter, Spread With No Adapter, Spread After the Adapter, Answers the Adapter's Way With No Adapter, Answers the Adapter's Way After the Adapter, Check Test Accuracy, Median Answer Time, Anticipations, Early Key Presses, Frame Interval, Refresh Rate, Dropped Frames, Test Duration, Adapter Time, Completed Trials and Planned Trials. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Motion Aftereffect Task used in research?
58 papers from 2021 to 2025 name it in their title or abstract, down 41% compared with 2016 to 2020. That ranks it 286 of 495 test families in the ConductCognition test census (use grade D). Source: ConductCognition test census 0.22.0, counted 3 November 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Motion Aftereffect Task have?
In the published research, 0 papers report its test-retest reliability and 0 registered clinical studies use it as an outcome (evidence grade D in the ConductCognition test census).
Does it report a percentile?
No. Scores and quality flags only.
Which settings can a researcher change?
Tests at each coherence (4 to 8). 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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