Attention
Occluded Shapes Task
Also called: amodal completion, primed matching, occlusion priming, mosaic interpretation
Measure visual completion by comparing matching times after complete, partly hidden and cut-out shapes.
5-7 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
- 69
- Evidence grade
- D
- Registered clinical studies
- 0
What it measures
Measure how vision completes partly hidden shapes. A complete, partly hidden or cut-out shape flashes before two shapes appear. Participants judge whether the pair is the same or different. Response times show whether a partly hidden shape primes its complete or cut-out form.
Constructs
- Amodal completion
- Visual object representation
- Perceptual priming
Research uses
- Visual perception research
- Object recognition research
How the paradigm works
The Occluded Shapes Task measures amodal completion: how vision represents a shape that is partly hidden. Participants see a complete shape, the same shape behind a blue rectangle, or just its visible fragment. They then judge whether two shapes are identical. Probe pairs show either the complete form or the cut-out form. Faster matching of complete probes after an occluded prime supports a completed representation.
More about the paradigm
The seeded plan crosses three prime types, two prime durations (100 and 300 ms), two probe forms and same or different answers. Six repetitions give 144 test trials, after 12 practice trials with feedback. Each trial has a 500 ms fixation, the prime, a 50 ms blank and up to 3000 ms to answer with the arrow keys. All conditions are set before the session. Shapes are original code drawings.
Scores
- Completion Biasms
- Complete-probe preference after an occluded prime minus that after a mosaic prime, equally averaged across 100 and 300 ms primes. Each cell needs three correct same-pair responses.
- Positive values indicate a shift toward the complete interpretation
- Complete-Probe Preference, Occluded Primems
- Median same-pair time for mosaic probes minus complete probes after occluded primes, equally averaged across durations.
- Positive values mean complete probes were matched faster
- Complete-Probe Preference, Complete Primems
- The same complete-probe preference after complete primes.
- Control for the complete interpretation
- Complete-Probe Preference, Mosaic Primems
- The same complete-probe preference after mosaic primes.
- Control for the visible fragment
- Completion Bias by Prime Durationms
- Completion bias keyed by prime duration in milliseconds.
- Compare effects across prime durations
- Matching Times by Conditionms
- Correct same-pair medians keyed by prime, duration and probe form; cells with fewer than three usable responses are omitted.
- Compare the occluded prime with both controls
- Accuracy%
- Share correct among trials whose displays ran on time; omissions and anticipations count as errors.
- Higher is better
- Accuracy by Prime%
- Accuracy in each of the three prime conditions.
- Check accuracy beside response time
- Median Correct Response Timems
- Median correct response time from probe onset, excluding responses under 100 ms and late displays.
- Shorter means faster matching
- Anticipationscount
- Responses under 100 ms after probe onset.
- Excluded from matching times
- Missed Responsescount
- Pairs without an arrow-key answer within 3000 ms.
- Fewer is better
- Early Key Pressescount
- Arrow presses before the probe pair appeared.
- Not taken as answers
- Displays on Time%
- Share of trials with prime and gap durations within one screen frame of plan.
- Below 0.9 is flagged
- Completed Trialstrials
- Test trials recorded in the selected run, including timed-out trials.
- Compare with planned trials
- Planned Trialstrials
- Number of test trials planned.
- Informational
Use and evidence
69 papers from 2021 to 2025 name this task in their title or abstract, down 7% compared with 2016 to 2020. That ranks it 307 of 582 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 20 |
| 2024 | 11 |
| 2023 | 10 |
| 2022 | 12 |
| 2021 | 16 |
| 2020 | 15 |
| 2019 | 14 |
| 2018 | 15 |
| 2017 | 16 |
| 2016 | 14 |
| 2015 | 9 |
| 2014 | 9 |
| 2013 | 11 |
| 2012 | 19 |
| 2011 | 12 |
| 2010 | 46 |
| 2009 | 11 |
| 2008 | 13 |
| 2007 | 14 |
| 2006 | 16 |
| 2005 | 6 |
| 2004 | 10 |
| 2003 | 10 |
| 2002 | 9 |
| 2001 | 14 |
| 2000 | 10 |
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
- 7
- Registered clinical studies using it as an outcome
- 0
Measured on ConductCognition
Pooled across the studies that feed our platform norms, by device group. A figure needs 50 or more people.
No pooled figure yet.
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 0.39.0, counted 8 November 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- Sequence
- 500 ms fixation, a prime for 100 or 300 ms, a 50 ms blank, then a pair for up to 3000 ms. The left arrow means same; the right arrow means different.
- Shapes
- Four original polygons. A blue rectangle hides the right portion in occluded primes. Mosaic primes retain the identical visible fragment without the rectangle. Probes show complete or mosaic shapes.
- Trials
- 3 prime types × 2 durations × 2 probe forms × 2 answers × 6 repeats = 144 test trials. Repeats range from 4 to 10, giving 96 to 240 trials. Every condition has balanced same and different answers. A break comes halfway.
- Practice
- 12 trials with 800 ms feedback, followed by the main trials without feedback.
- Score
- Completion bias is the complete-probe preference after occluded primes minus that after mosaic primes. Preference is median correct same-pair time for mosaic probes minus complete probes. Durations have equal weight. Each cell needs 3 usable responses.
- Timing
- Frame-based displays save measured prime and gap durations. Trials more than one frame off plan leave the scores. Responses under 100 ms leave the matching-time contrast. Fewer than 90% of displays on time is flagged.
- Interpretation
- Compare the complete, occluded and mosaic conditions across groups. Small differences in one person are not an ability rank. No percentile is computed.
A primed-matching adaptation of Sekuler and Palmer, with original polygons, fixed 100 and 300 ms primes, a 50 ms gap, a 3000 ms response limit and median-based contrasts. These settings and quality limits are ConductScience choices. It does not reproduce the paper's items or norms.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scores test pairs from the run with the most trials, ties going to the latest run. Chance is 1 in 2. Each contrast needs three correct same-pair responses per prime, duration and probe form. A short run, missing contrast or fewer than 90% of displays on time is flagged. Omissions and responses under 100 ms follow the timed-test rule.
Why these rules
Priming is a contrast between matching times, so errors, anticipations and late displays leave it. Minimum cell counts and timing checks are ConductScience quality rules.
No percentile. Scores and quality flags only.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Trials per condition | 6 | 4 to 10 |
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 Occluded Shapes Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Sekuler and Palmer, 1992), with the standard settings (trials per condition: 6). The main score was completion bias (complete-probe preference after an occluded prime minus that after a mosaic prime, equally averaged across 100 and 300 ms primes).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Sekuler, A. B., & Palmer, S. E. (1992). Perception of partly occluded objects: A microgenetic analysis. Journal of Experimental Psychology: General, 121(1), 95-111. https://doi.org/10.1037/0096-3445.121.1.95Primed matching to compare complete and mosaic interpretations of an occluded shape.
Source papers
- Sekuler AB, Palmer SE (1992). Perception of partly occluded objects: A microgenetic analysis. Journal of Experimental Psychology: General, 121(1), 95-111.Paradigm source, Adults
Questions
How long does the Occluded Shapes Task take?
About 5 to 7 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?
Completion Bias, Complete-Probe Preference, Occluded Prime, Complete-Probe Preference, Complete Prime, Complete-Probe Preference, Mosaic Prime, Completion Bias by Prime Duration, Matching Times by Condition, Accuracy, Accuracy by Prime, Median Correct Response Time, Anticipations, Missed Responses, Early Key Presses, 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 Occluded Shapes Task used in research?
69 papers from 2021 to 2025 name it in their title or abstract, down 7% compared with 2016 to 2020. That ranks it 307 of 582 test families in the ConductCognition test census (use grade D). Source: ConductCognition test census 0.39.0, counted 8 November 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Occluded Shapes 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 (4 to 10). 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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