Processing Speed
Symbol Coding Test
Measure high-throughput processing speed and visual-motor matching with a browser-native coding task.
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. Try it here first, with no account.
- Papers, 2021 to 2025
- 2,557
- Evidence grade
- A
- Registered clinical studies
- 1,457
What it measures
Measures processing speed and visual-motor mapping by requiring rapid symbol-to-key matching under time pressure.
Constructs
- Processing speed
- Visual-motor mapping
- Sustained task efficiency
- Response consistency under time pressure
Research uses
- General cognitive slowing assessment
- Intervention response monitoring
- Neuropsychiatric profile batteries
- Baseline and follow-up speed tracking
How the paradigm works
Symbol Coding measures cognitive processing speed by presenting a fixed symbol-to-key legend and requiring rapid symbol-key matching across repeated trials. Each response combines visual lookup, short-term mapping retention, and motor execution under time pressure.
More about the paradigm
Because the mapping remains stable during a block, early trials emphasize visual search while later trials increasingly reflect automatization efficiency. The task is therefore sensitive to both pure speed and consistency under sustained pace.
Computerized symbol coding variants are widely used in neuropsychology and clinical-trial settings as practical indices of psychomotor and cognitive speed.
Scores
- Accuracy%
- Proportion of symbol trials answered correctly.
- Higher is better
- Mean Correct RTms
- Average response latency on correct trials.
- Lower is better
- Median Correct RTms
- Median response latency on correct trials.
- Lower is better
- Throughputcorrect/min
- Correct responses per minute of test time, from the first test item to the last. Instructions and practice are not counted.
- Higher is better
- Total Correctcount
- Count of correctly matched symbols.
- Higher is better
- Total Errorscount
- Incorrect or missed symbol responses.
- Lower is better
Use and evidence
2,557 papers from 2021 to 2025 name this task in their title or abstract, up 48% compared with 2016 to 2020. That ranks it 9 of 670 test families in our census. The Symbol Key Game page shows these counts too, as those of the published test the game is compared with. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 626 |
| 2024 | 589 |
| 2023 | 499 |
| 2022 | 428 |
| 2021 | 415 |
| 2020 | 439 |
| 2019 | 362 |
| 2018 | 342 |
| 2017 | 307 |
| 2016 | 280 |
| 2015 | 255 |
| 2014 | 272 |
| 2013 | 209 |
| 2012 | 175 |
| 2011 | 150 |
| 2010 | 148 |
| 2009 | 133 |
| 2008 | 123 |
| 2007 | 100 |
| 2006 | 115 |
| 2005 | 82 |
| 2004 | 69 |
| 2003 | 74 |
| 2002 | 58 |
| 2001 | 50 |
| 2000 | 62 |
Use grade A
1,000 or more papers from 2021 to 2025.
Evidence grade A
At least 25 papers report its test-retest reliability and at least 25 registered clinical studies use it as an outcome.
- Papers on test-retest reliability
- 135
- Papers on reliability or validity
- 860
- Registered clinical studies using it as an outcome
- 1,457
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 0.48.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: symbol-coding_test, four keys (chance 25%, 12 trials per symbol) within 3 s. Below chance invalidates and not above chance is flagged. One key on 90% of answers invalidates when accuracy is not above chance. Missed responses and responses under 100 ms follow the timed-test rule.
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). Missed responses and responses under 100 ms keep the platform's timed-test rule: more than max(3, 25%) missed responses or more than max(2, 20%) responses under 100 ms invalidate, and any is flagged. A response under 100 ms cannot be a reaction to the stimulus.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Number of test trials | 48 | 24 to 96 |
| Trial timeout (ms) | 3,000 | 1,500 to 5,000 |
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.
Included in these batteries
Each battery runs this test with others in a fixed order, with standard settings.
- Older Adult Executive Speed Battery4 tests, 20 minutes per participant
Cite and describe
Participants completed the Symbol Coding task in a web browser (ConductCognition task version 1.0.0, scoring version 2.0.0; Wechsler, 1981; Smith, 1982), with the standard settings (number of test trials: 48; trial timeout (ms): 3,000). The main score was throughput (correct responses per minute of test time, from the first test item to the last).
Paradigm source: Wechsler (1981); Smith (1982).
ConductCognition versions: task version 1.0.0, scoring version 2.0.0. Every export records the versions each session used, for a methods section.
Source papers
- No platform-matched normative source is currently seeded for this task in ConductCognition.Paradigm source, N/A
Questions
How long does the Symbol Coding Test 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?
Accuracy, Mean Correct RT, Median Correct RT, Throughput, Total Correct and Total Errors. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Symbol Coding Test used in research?
2,557 papers from 2021 to 2025 name it in their title or abstract, up 48% compared with 2016 to 2020. That ranks it 9 of 670 test families in the ConductCognition test census (use grade A). Source: ConductCognition test census 0.48.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Symbol Coding Test have?
In the published research, 135 papers report its test-retest reliability and 1,457 registered clinical studies use it as an outcome (evidence grade A in the ConductCognition test census).
Which settings can a researcher change?
Number of test trials (24 to 96) and trial timeout (ms) (1,500 to 5,000). 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.
Run this test in your next study
Start free with 10 free participants on any test, then use participant credits or a yearly plan.