Attention
Glass Pattern Task
Also called: Glass patterns, form coherence task, global form coherence, concentric Glass pattern, dipole pattern, form coherence threshold
Measure global form perception: how many dot pairs must line up along circles before people see the circular pattern among pairs at random angles.
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. Preview any test free after you sign up.
- Papers, 2021 to 2025
- 38
- Evidence grade
- C
- Registered clinical studies
- 1
What it measures
Measures global form perception: how many dot pairs must line up along circles before a person sees the circular pattern. Two displays of 150 dot pairs flash one after the other; in one, a share of the pairs (the coherence) lies along circles around the center. Participants press 1 or 2 for the display with the circles. The coherence comes from six fixed levels, and the score is the coherence at which 75 percent of answers are right.
Constructs
- Global form perception
- Orientation pooling
- Visual integration
Research uses
- Form perception research
- Within-study group comparison
- Individual differences in global form sensitivity
How the paradigm works
The Glass Pattern Task measures global form perception: how many dot pairs must line up along circles before a person sees the circular pattern. Each trial flashes two displays of 150 white dot pairs on black, for 167 ms each with a cross for 500 ms between them. In one display a share of the pairs, the coherence, lies along circles around the center (a concentric Glass pattern); every other pair, and every pair of the other display, is turned at random. The participant then presses 1 or 2 for the display with the circles, with no time limit.
More about the paradigm
The displays follow Glass (1969) and Wilson and Wilkinson (1998), detected in two intervals as in Mandelli and Kiper (2005) and Badcock, Almeida and Dickinson (2013): dots 4 px across, the two dots of a pair 8 px apart, in a circle 400 px across, so each dot's partner is plain to see. 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; the window size and pixel ratio are saved on every trial. Six coherence levels (6, 10, 16, 24, 40 and 64%) each appear 24 times (standard; 12 to 40) with the pattern in each display on half the trials, for 144 trials in a seeded order with a break halfway, after 6 practice trials with feedback. Nothing a participant answers changes a coherence: there is no staircase. The displays switch on screen frames, and their measured durations are saved on every trial. Desktop and laptop only; about 6 to 8 minutes.
The main score is the coherence threshold: the coherence at which a two-choice Weibull, fitted by maximum likelihood to the share right at each level as in the random dot motion task, reaches 75 percent right. Lower means a weaker pattern was enough. Accuracy at each coherence, any lean toward the first or the second display and the screen's timing are also reported. Scores support research and do not diagnose.
Scores
- Coherence Threshold%
- Share of dot pairs along the circles at which the fitted Weibull function reaches 75 percent right.
- Lower means a weaker pattern 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 patterns strong enough to see.
- Lower means fewer lapses
- Accuracy%
- Share of usable answers that named the display with the circles.
- Higher is better; guessing gives 0.5
- Accuracy by Coherence%
- Share right at each coherence level, keyed by the coherence in percent.
- Rises with coherence
- First Display Answers%
- Share of usable answers that named the first display.
- 0.5 means no lean toward either display
- Accuracy, Circles in the First Display%
- Share right when the circles were in the first display.
- Informational
- Accuracy, Circles in the Second Display%
- Share right when the circles were in the second display.
- Informational
- Median Answer Timems
- Median time from the question to the answer.
- Informational; the answer has no time limit
- Anticipationscount
- Answers given within 100 ms of the question, which leave the score.
- More than max(2, 20%) is invalid
- Early Key Pressescount
- 1 or 2 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 two displays each ran 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
38 papers from 2021 to 2025 name this task in their title or abstract, up 15% compared with 2016 to 2020. That ranks it 274 of 395 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 12 |
| 2024 | 7 |
| 2023 | 4 |
| 2022 | 8 |
| 2021 | 7 |
| 2020 | 4 |
| 2019 | 8 |
| 2018 | 8 |
| 2017 | 6 |
| 2016 | 7 |
| 2015 | 3 |
| 2014 | 9 |
| 2013 | 12 |
| 2012 | 13 |
| 2011 | 5 |
| 2010 | 33 |
| 2009 | 5 |
| 2008 | 0 |
| 2007 | 2 |
| 2006 | 7 |
| 2005 | 8 |
| 2004 | 4 |
| 2003 | 2 |
| 2002 | 5 |
| 2001 | 6 |
| 2000 | 4 |
Use grade D
30 to 99 papers from 2021 to 2025.
Evidence grade C
At least 2 test-retest papers, 30 reliability or validity papers or 3 registered clinical studies.
- Papers on test-retest reliability
- 2
- Papers on reliability or validity
- 6
- Registered clinical studies using it as an outcome
- 1
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 2 November 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- Display
- On a black panel 480 px square: a cross for 500 ms, then 150 white dot pairs in a circle 400 px across for 167 ms, the cross for 500 ms, then a second display of 150 pairs for 167 ms. Dots are 4 px across, and the two dots of a pair are 8 px apart.
- Pattern
- In one of the two displays a share of the pairs, the coherence, lies along circles around the center: each such pair is turned at right angles to the line from the center. Every other pair, and every pair of the other display, is turned at random, and the pattern's pairs are placed like the others.
- Coherence
- 6, 10, 16, 24, 40 or 64% of the pairs, 9 to 96 of the 150.
- Answer
- Press 1 or 2 for the display with the circles, with no time limit. Keys pressed before the question are counted and not taken as answers.
- Trials
- 24 at each coherence (standard; 12 to 40): 144 trials in a seeded order, with the pattern in each display on half the trials at every level, and a break after every 72 trials.
- Practice
- 6 trials, 2 with every pair on the circles and 2 at each of the two strongest levels, with feedback for 1,000 ms.
- Fixed levels
- Every coherence and display time is set before the session, and no answer changes it: there is no staircase. Each display shows for 10 frames of a 60 Hz screen, in whole frames of the screen's own rate.
- Screen
- Sizes are CSS pixels with no screen calibration. A dot is 4 px on every desktop or laptop the test runs on, drawn at the screen's own pixel ratio, so its visual angle depends on the screen's pixel pitch and the viewing distance. The window size and pixel ratio are saved on every trial.
- Score
- The coherence at which 75 percent of answers are right, from the random dot motion task's two-choice Weibull, fitted by maximum likelihood to the share right at each level. Answers under 100 ms and trials whose displays ran more than one frame off plan leave the score.
Glass pattern studies differ in the structure (concentric, radial or parallel), the number of pairs and the display time, and many set the coherence with a staircase. This version uses concentric patterns, six fixed coherence levels (the method of constant stimuli) and two displays one after the other, so its threshold is compared within this version.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: form_coherence_test from the scored run, 1 or 2 for the display with the circles, after both displays, with no time limit (chance 50%; the pattern is in each display on half the trials at every level), graded from the saved key and pattern display. Below chance invalidates and not above chance is flagged; one key 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. No fitted coherence threshold, a run short of its planned trials, or fewer than 90% of trials with both displays 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. The displays flash for a set time, so trials whose displays ran off plan leave the score, and a threshold above the strongest level shown cannot be estimated.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Trials per coherence level | 24 | 12 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.
- Recruiting online? See the setup guides for Prolific, Sona Systems, CloudResearch Connect and Qualtrics.
Cite and describe
Participants completed the Glass Pattern Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Glass, 1969; Wilson and Wilkinson, 1998), with the standard settings (trials per coherence level: 24). The main score was coherence threshold (share of dot pairs along the circles at which the fitted Weibull function reaches 75 percent right).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Glass, L. (1969). Moiré effect from random dots. Nature, 223(5206), 578-580. https://doi.org/10.1038/223578a0Random dots laid over a turned copy of themselves show circles: the Glass pattern.
- Wilson, H. R., & Wilkinson, F. (1998). Detection of global structure in Glass patterns: Implications for form vision. Vision Research, 38(19), 2933-2947. https://doi.org/10.1016/S0042-6989(98)00109-6Concentric patterns, detected among random pairs, give the lowest thresholds of the structures tested.
- Mandelli, M.-J. F., & Kiper, D. C. (2005). The local and global processing of chromatic Glass patterns. Journal of Vision, 5(5), 2. https://doi.org/10.1167/5.5.2Coherence as the share of pairs along the circles, with a pattern and a random display in two intervals.
- Badcock, D. R., Almeida, R. A., & Dickinson, J. E. (2013). Detecting global form: Separate processes required for Glass and radial frequency patterns. Frontiers in Computational Neuroscience, 7, 53. https://doi.org/10.3389/fncom.2013.00053Fixed coherence levels in two intervals of 160 ms, and the coherence for 75 percent right.
Source papers
- Wilson HR, Wilkinson F (1998). Detection of global structure in Glass patterns: implications for form vision. Vision Research, 38(19):2933-2947.Paradigm source, Adults
Questions
How long does the Glass Pattern 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?
Coherence Threshold, Psychometric Slope, Lapse Rate, Accuracy, Accuracy by Coherence, First Display Answers, Accuracy, Circles in the First Display, Accuracy, Circles in the Second Display, 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 Glass Pattern Task used in research?
38 papers from 2021 to 2025 name it in their title or abstract, up 15% compared with 2016 to 2020. That ranks it 274 of 395 test families in the ConductCognition test census (use grade D). Source: ConductCognition test census 0.14.0, counted 2 November 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Glass Pattern Task have?
In the published research, 2 papers report its test-retest reliability and 1 registered clinical study uses it as an outcome (evidence grade C in the ConductCognition test census).
Which settings can a researcher change?
Trials per coherence level (12 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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