Attention
Object Substitution Masking Task
Also called: OSM, four-dot masking, common onset masking, masking by object substitution
Measure masking by four dots that stay after a brief display: how much less often people name a target ring's gap when the dots around it linger.
6-8 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
- 17
- Evidence grade
- D
- Registered clinical studies
- 0
What it measures
A measure of masking by four dots that stay after a brief display. Rings with a gap flash for about 50 ms in a circle around the cross, 1, 8 or 16 at a time, and four dots mark one of them. The dots either go with the rings or stay alone for about 200 ms more. Participants press the arrow key for the side of the marked ring's gap, with no time limit. The score is the accuracy lost when the dots stay, at each number of rings.
Constructs
- Visual masking
- Object substitution
- Spatial attention
- Visual awareness
Research uses
- Visual attention and awareness research
- Research on reentrant and object-updating accounts of masking
- Within-study comparison of masking across conditions or groups
How the paradigm works
The Object Substitution Masking Task measures how a briefly shown target is lost when the four dots that mark it stay on after it has gone (Enns and Di Lollo, 1997; Di Lollo, Enns and Rensink, 2000). The dots never touch or cover the target. When they go with the display, the target is seen; when they stay, fewer targets are reported, and the space inside the dots can look empty. Di Lollo and colleagues found this masking grew with the number of items on the screen and with the time the dots stayed. Later studies found the number of items changes it little once accuracy is kept off its ceiling (Argyropoulos, Gellatly, Pilling and Carter, 2013; Filmer, Mattingley and Dux, 2014).
More about the paradigm
On each trial a cross shows for 500 ms, then 1, 8 or 16 rings for about 50 ms (3 frames of a 60 Hz screen) at places on a circle around it. Each ring has a gap at the top, bottom, left or right, and four small dots surround one ring, the target. The dots then either go with the rings (the common offset, the control) or stay alone for about 200 ms (12 frames). After a common offset the screen stays blank as long, so the question comes at the same moment in both. Participants press the arrow key for the side of the target's gap, with no time limit; keys pressed earlier are not taken. Each number of rings runs 24 times with each kind of dots (standard; 16 to 40), for 144 trials in a seeded order with two short breaks, after 6 practice trials with feedback, the first two slower. Every display time is set before the session: no answer changes a later display, and there is no training mode. Displays switch on screen frames, the measured durations are saved on every trial, and trials more than one frame off plan leave the score. Desktop and laptop only; about 6 to 8 minutes.
The main score is the masking effect: accuracy with a common offset minus accuracy with trailing dots, averaged over the three numbers of rings. The same difference at 1, 8 and 16 rings, its change from 1 to 16 rings, each condition's accuracy and the screen's timing are also reported. Scores support research and do not diagnose.
Scores
- Masking Effect%
- Accuracy when the dots went with the rings minus accuracy when they stayed, averaged over 1, 8 and 16 rings.
- Above 0 means the staying dots masked the target; a difference between conditions
- Masking Effect, 1 Ring%
- Accuracy with a common offset minus accuracy with trailing dots, when the target was the only ring.
- Informational; often near 0 or held down by a ceiling
- Masking Effect, 8 Rings%
- The same difference with 8 rings on the screen.
- Informational
- Masking Effect, 16 Rings%
- The same difference with 16 rings on the screen.
- Informational
- Masking Change from 1 to 16 Rings%
- The masking effect with 16 rings minus the masking effect with 1 ring.
- Above 0 means more masking with more rings; read with the ceiling at 1 ring in mind
- Accuracy, Dots Gone%
- Share right when the dots went with the rings, over all numbers of rings.
- Higher is better; chance is 0.25
- Accuracy, Dots Staying%
- Share right when the dots stayed alone for about 200 ms, over all numbers of rings.
- Chance is 0.25
- Accuracy, Dots Gone, by Rings%
- Share right with a common offset at 1, 8 and 16 rings, keyed by the number of rings.
- Falls as rings are added
- Accuracy, Dots Staying, by Rings%
- Share right with trailing dots at 1, 8 and 16 rings, keyed by the number of rings.
- Informational
- Accuracy%
- Share right over all scored trials.
- Chance is 0.25
- Median Answer Timems
- Median time from the question to the answer.
- Informational; the answer has no time limit
- Anticipationscount
- Answers under 100 ms from the question, which are not scored.
- Lower is better
- Early Key Pressescount
- Arrow keys pressed before the question appeared, 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 refresh rate from the frame interval.
- Informational
- Displays on Time%
- Share of answered trials whose rings and the screen after them each showed within one frame of plan; only these are scored.
- Under 0.9 is flagged for review
- Completed Trialstrials
- Trials answered in the scored run.
- Fewer than planned is flagged for review
- Planned Trialstrials
- Trials the run set out to show.
- Informational
Use and evidence
17 papers from 2021 to 2025 name this task in their title or abstract, down 41% compared with 2016 to 2020. That ranks it 418 of 495 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 0 |
| 2024 | 5 |
| 2023 | 1 |
| 2022 | 7 |
| 2021 | 4 |
| 2020 | 2 |
| 2019 | 4 |
| 2018 | 4 |
| 2017 | 9 |
| 2016 | 10 |
| 2015 | 15 |
| 2014 | 19 |
| 2013 | 16 |
| 2012 | 14 |
| 2011 | 11 |
| 2010 | 26 |
| 2009 | 7 |
| 2008 | 8 |
| 2007 | 5 |
| 2006 | 10 |
| 2005 | 5 |
| 2004 | 8 |
| 2003 | 3 |
| 2002 | 2 |
| 2001 | 1 |
| 2000 | 0 |
Use grade E
Fewer than 30 papers from 2021 to 2025.
Evidence grade D
Little published measurement evidence found.
- Papers on test-retest reliability
- 0
- Papers on reliability or validity
- 2
- 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 2 November 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- Display
- On a dark panel: a cross for 500 ms, then 1, 8 or 16 rings 28 px across at 16 places on a circle 150 px from the cross, each with a gap at the top, bottom, left or right, and four 4 px dots around one ring, the target.
- Durations
- The rings and dots show for 3 frames of a 60 Hz screen, about 50 ms. The dots then go with the rings (common offset) or stay alone for 12 frames, about 200 ms; after a common offset the screen stays blank as long. Durations are whole frames of the screen's own rate.
- Answer
- Press the arrow key for the side of the target's gap, with no time limit. Keys pressed before the question are counted and not taken as answers.
- Trials
- 24 for each number of rings with each kind of dots (standard; 16 to 40): 144 trials in a seeded order, with the target's gap on each side equally often in each condition and a short break after every 48.
- Practice
- 6 trials with feedback for 1,000 ms; the first two show the rings for 12 frames, about 200 ms.
- Fixed times
- Every display time is set before the session, and no answer changes it: there is no staircase and no training mode.
- Score
- The masking effect: accuracy with a common offset minus accuracy with trailing dots, averaged over 1, 8 and 16 rings. Trials whose rings or following screen ran more than one frame off plan, and answers under 100 ms, leave the score.
The display is drawn in screen pixels with no calibration, on a circle so every ring is the same distance from the cross. The rings show for whole frames of a 60 Hz screen, about 50 ms, where the founding experiments used 10 and 45 ms. The scores support research and do not diagnose.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: object_substitution_masking_test from the scored run, an arrow key for the side of the target's gap after the display, with no time limit (chance 25%; the target's gap is on each of the four sides equally often in every cell), graded from the saved gap. Below chance invalidates and not above chance is flagged; one arrow on 90% of answers invalidates when accuracy is not above chance. Answer times run from the question. Responses under 100 ms follow the timed-test rule. Under 50% right with one ring and a common offset, no masking effect, a run short of its planned trials, or fewer than 90% of trials with the rings and the screen after them within one frame of plan 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). An answer under 100 ms from the question was pressed before the question could be read. One ring with dots that go with it is the easiest display, so accuracy under 50% there means the rings could not be seen at this display time or the task was not followed. The display time and the time the dots linger carry the score, so trials that ran late leave it.
No percentile. Scores and quality flags only.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Trials per condition | 24 | 16 to 40 |
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 Object Substitution Masking Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Di Lollo, Enns and Rensink, 2000; Enns and Di Lollo, 1997), with the standard settings (trials per condition: 24). The main score was masking effect (accuracy when the dots went with the rings minus accuracy when they stayed, averaged over 1, 8 and 16 rings).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Di Lollo, V., Enns, J. T., & Rensink, R. A. (2000). Competition for consciousness among visual events: The psychophysics of reentrant visual processes. Journal of Experimental Psychology: General, 129(4), 481-507. https://doi.org/10.1037/0096-3445.129.4.481The task: rings with a gap on one of four sides, the target marked by four dots that also mask it, up to 16 rings, and masking that grew with the number of rings and the time the dots stayed.
- Enns, J. T., & Di Lollo, V. (1997). Object substitution: A new form of masking in unattended visual locations. Psychological Science, 8(2), 135-139. https://doi.org/10.1111/j.1467-9280.1997.tb00696.x
- Argyropoulos, I., Gellatly, A., Pilling, M., & Carter, W. (2013). Set size and mask duration do not interact in object-substitution masking. Journal of Experimental Psychology: Human Perception and Performance, 39(3), 646-661. https://doi.org/10.1037/a0030240The rings on a circle, the common offset as the control, and no interaction of set size with the dots' duration once accuracy is kept off its ceiling.
- Filmer, H. L., Mattingley, J. B., & Dux, P. E. (2014). Size (mostly) doesn't matter: The role of set size in object substitution masking. Attention, Perception, & Psychophysics, 76(6), 1620-1629. https://doi.org/10.3758/s13414-014-0692-5Set sizes of 1, 8 and 16, a blank that keeps the question at the same moment after every mask, and similar masking with 8 and 16 items.
- Goodhew, S. C., Pratt, J., Dux, P. E., & Ferber, S. (2013). Substituting objects from consciousness: A review of object substitution masking. Psychonomic Bulletin & Review, 20(5), 859-877. https://doi.org/10.3758/s13423-013-0400-9
Source papers
- Di Lollo V, Enns JT, Rensink RA (2000). Competition for consciousness among visual events: The psychophysics of reentrant visual processes. Journal of Experimental Psychology: General, 129(4):481-507.Paradigm source, Adults
- No normative data for this task.Paradigm source, N/A
Questions
How long does the Object Substitution Masking Task take?
About 6 to 8 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?
Masking Effect, Masking Effect, 1 Ring, Masking Effect, 8 Rings, Masking Effect, 16 Rings, Masking Change from 1 to 16 Rings, Accuracy, Dots Gone, Accuracy, Dots Staying, Accuracy, Dots Gone, by Rings, Accuracy, Dots Staying, by Rings, Accuracy, Median Answer Time, Anticipations, Early Key Presses, Frame Interval, Refresh Rate, Displays on Time, Completed Trials and Planned Trials. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Object Substitution Masking Task used in research?
17 papers from 2021 to 2025 name it in their title or abstract, down 41% compared with 2016 to 2020. That ranks it 418 of 495 test families in the ConductCognition test census (use grade E). Source: ConductCognition test census 0.22.0, counted 2 November 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Object Substitution Masking 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?
Trials per condition (16 to 40). 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.
Every test: the full test list.
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