Processing Speed
Symbol Scan Task
Also called: symbol search task, symbol search paradigm, target symbol search
Measure processing speed in the symbol search format: two target symbols above a row of five, answered yes or no against the clock, scored by right minus wrong answers.
4-5 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
- 143
- Evidence grade
- B
- Registered clinical studies
- 129
What it measures
A timed measure of processing speed. Two target symbols sit above a row of five, and the person answers whether either target is in the row, as fast as they can without many errors. The symbols are drawn for this test. The score is right answers minus wrong answers over two timed rounds.
Constructs
- Processing speed
- Visual scanning
- Perceptual speed
Research uses
- Processing speed research
- Aging and cognition research
- Within-study group comparison
How the paradigm works
The Symbol Scan Task measures processing speed in the symbol search format: two target symbols and a row of five, and the person decides, as fast as they can, whether either target is in the row. Intelligence scales use this format as a speed subtest, two targets and a group of five, answered for 2 minutes and scored as right answers minus wrong answers (Droit-Volet and Zelanti, 2013; Kanmogne and colleagues, 2020). Liebel and colleagues (2015) built a computer version with the targets above the group and two answer buttons, a new item after each answer and symbols of their own; it agreed with the paper subtest and between two sessions.
More about the paradigm
In this test the targets sit in a frame above the row. The person presses F if one of them is in the row and J if neither is, and the next item follows at once. Half the items hold one target, at a place spread evenly over the row. Every row also holds a near miss, a target's mirror image, so the answer needs a careful look. The symbols are 40 figures of four strokes drawn by ConductScience code; none comes from a published test. Six practice items with feedback come first, then two timed rounds of 60 seconds as standard, each with a time bar.
The primary score is net correct, right answers minus wrong answers, so guessing faster gains nothing. The test also reports right and wrong answers, accuracy, the median time of right answers and the same split by rows with and without a target: a row with no target has to be checked to the end. Answers under 100 ms count as neither right nor wrong. The score is not on the scale of any published subtest, and no published norms apply. Scores support research and do not diagnose.
Scores
- Net Correctscore
- Right answers minus wrong answers across all rounds.
- Higher means faster accurate scanning
- Right Answersitems
- Right answers at or after 100 ms.
- Higher is better
- Wrong Answersitems
- Wrong answers at or after 100 ms.
- Lower is better
- Answered Itemsitems
- Items answered with a key, anticipations included.
- Under 10 a minute invalidates the session
- Accuracy%
- Right answers as a share of right and wrong answers.
- Under 70% invalidates the session
- Median Correct Response Timems
- Median time from the item to the key, over right answers.
- Lower is faster
- Median Time, Target in Rowms
- Median time of right answers on rows that hold a target.
- Lower is faster
- Median Time, No Targetms
- Median time of right answers on rows with no target.
- Usually slower than with a target: the whole row is checked
- Accuracy, Target in Row%
- Share right on rows that hold a target.
- Higher is better
- Accuracy, No Target%
- Share right on rows with no target.
- Higher is better
- Anticipationscount
- Answers under 100 ms, which count as neither right nor wrong.
- Lower is better
- Completed Roundscount
- Rounds with at least one item shown.
- Fewer than planned invalidates the session
- Planned Roundscount
- Rounds in the session's plan.
- Set by the settings
- Test Timeseconds
- The time limits of the rounds shown, added together.
- Set by the settings
Use and evidence
143 papers from 2021 to 2025 name this task in their title or abstract, up 8% compared with 2016 to 2020. That ranks it 157 of 395 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 41 |
| 2024 | 28 |
| 2023 | 32 |
| 2022 | 16 |
| 2021 | 26 |
| 2020 | 28 |
| 2019 | 41 |
| 2018 | 18 |
| 2017 | 22 |
| 2016 | 24 |
| 2015 | 11 |
| 2014 | 21 |
| 2013 | 20 |
| 2012 | 19 |
| 2011 | 13 |
| 2010 | 10 |
| 2009 | 7 |
| 2008 | 9 |
| 2007 | 8 |
| 2006 | 6 |
| 2005 | 5 |
| 2004 | 3 |
| 2003 | 5 |
| 2002 | 6 |
| 2001 | 6 |
| 2000 | 7 |
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
- 12
- Papers on reliability or validity
- 84
- Registered clinical studies using it as an outcome
- 129
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.
- Item
- Two target symbols in a frame above a row of five, until a key is pressed or the round's time runs out. The next item follows at once.
- Rows
- Half the rows hold one target, at a place spread evenly over the row, and every 4 items hold 2 of each answer. Every row also holds a near miss: a target's mirror image.
- Symbols
- 40 figures of 4 strokes on a grid of 3 by 3 points, drawn by code and checked by eye so none looks like a letter, digit or common sign. None comes from a published test.
- Rounds
- 2 rounds of 60 seconds (standard; 2, 3 or 4 rounds of 30 to 120 seconds), each with a time bar.
- Keys
- F for yes and J for no, shown on screen and read without case.
- Practice
- 6 items with feedback and no time limit.
- Score
- Right answers minus wrong answers. Answers under 100 ms count as neither, and an item cut off by the time limit counts for nothing.
Intelligence scales give this format on paper, with their own symbols, layout and norms. This test shows one item at a time with its own symbols, so its scores are not on the scale of any published subtest.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: symbol_search_test from the scored run, yes or no key presses in timed rounds. Chance is 1 in 2, and the correct keys are balanced. An item cut off when a round's time runs out is not a missed response. Below-chance accuracy, one key on 90% of answers when accuracy is not above chance, or more than max(2, 20%) answers under 100 ms invalidate. Fewer rounds than planned, fewer than 10 answers a minute, or accuracy under 70% over at least 12 answers invalidate.
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 cannot be a reaction to the item. The answer is always clear with time, so accuracy is not what this test measures: errors are few in a person who is scanning, and a person pressing one key gets half right. Net correct also grows with speed, so a fast guesser at 70% could score well; that is why low accuracy invalidates here rather than being flagged. Fewer than 10 answers a minute is too few to show speed, and net correct is only comparable when every planned round ran. These limits are ConductScience choices, the ones Pattern and Letter Comparison uses.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Round length (seconds) | 60 | 30 to 120 |
| Rounds | 2 | 2, 3, 4 |
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 Symbol Scan Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Liebel et al., 2015), with the standard settings (round length (seconds): 60; rounds: 2). The main score was net correct (right answers minus wrong answers across all rounds).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Liebel, S. W., Clark, U. S., Xu, X., Riskin-Jones, H. H., Hawkshead, B. E., Schwarz, N. F., Labbe, D., Jerskey, B. A., & Sweet, L. H. (2015). An FMRI-compatible Symbol Search task. Journal of the International Neuropsychological Society, 21(3), 231-238. https://doi.org/10.1017/S1355617715000144A computer version with the targets above the group, two answer buttons, a new item after each answer and symbols of its own.
- Droit-Volet, S., & Zélanti, P. S. (2013). Development of time sensitivity and information processing speed. PLoS ONE, 8(8), e71424. https://doi.org/10.1371/journal.pone.0071424The format: two targets, rows of five, 2 minutes, and right minus wrong answers.
Source papers
- Liebel SW, Clark US, Xu X, Riskin-Jones HH, Hawkshead BE, Schwarz NF, Labbe D, Jerskey BA, Sweet LH (2015). An FMRI-compatible Symbol Search task. Journal of the International Neuropsychological Society, 21(3):231-238.Paradigm source, Adults
Questions
How long does the Symbol Scan Task take?
About 4 to 5 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?
Net Correct, Right Answers, Wrong Answers, Answered Items, Accuracy, Median Correct Response Time, Median Time, Target in Row, Median Time, No Target, Accuracy, Target in Row, Accuracy, No Target, Anticipations, Completed Rounds, Planned Rounds and Test Time. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Symbol Scan Task used in research?
143 papers from 2021 to 2025 name it in their title or abstract, up 8% compared with 2016 to 2020. That ranks it 157 of 395 test families in the ConductCognition test census (use grade C). Source: ConductCognition test census 0.14.0, counted 2 November 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Symbol Scan Task have?
In the published research, 12 papers report its test-retest reliability and 129 registered clinical studies use it as an outcome (evidence grade B in the ConductCognition test census).
Which settings can a researcher change?
Round length (seconds) (30 to 120) and rounds (2, 3, 4). 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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