Processing Speed
SNARC Parity Task
Also called: SNARC effect task, spatial-numerical association of response codes, parity judgment task, MARC effect, mental number line task
Measure the SNARC effect: participants say whether digits are odd or even with a left and a right key, and large digits speed the right hand against the left.
9-11 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
- 26
- Evidence grade
- D
- Registered clinical studies
- 0
What it measures
A measure of how number size links to left and right. Digits from 1 to 9 appear one at a time, and participants press F or J to say whether each is odd or even, with the keys swapped between blocks. The main score is the SNARC slope: how much faster the right hand becomes, against the left, as the digits get larger.
Constructs
- Spatial-numerical association
- Number magnitude processing
- Parity judgment
- Processing speed
Research uses
- Numerical cognition research
- Math learning and dyscalculia research
- Studies of reading direction and culture
- Within-study group comparison
How the paradigm works
The SNARC Parity Task measures how number size links to left and right. Dehaene, Bossini and Giraux (1993) asked people whether digits were odd or even, with one key for each hand. Size had nothing to do with the answer, yet small digits were answered faster with the left hand and large digits faster with the right: the spatial-numerical association of response codes, or SNARC effect. It is read as a sign that numbers are laid out on a mental line from left to right, and it faded or reversed in readers of a right-to-left script.
More about the paradigm
Each trial shows a blank for 500 ms and a cross for 300 ms, then one digit from 1 to 9 without 5 until F or J or 2,000 ms. F is pressed with the left hand and J with the right. In two blocks F means odd, and in the other two F means even, in the order A, B, B, A, with the first drawn for each session. Each block shows each digit 10 times (standard; 6 to 12) in a seeded order with no digit twice in a row and at most three odd, even, small or large digits in a row: 320 trials, 20 answers per digit with each hand. Each time the keys change, 8 practice trials with feedback come first. About 9 to 11 minutes. The blank, the cross and the digit switch on screen frames, and response times run from the frame that drew the digit. Desktop and laptop only.
For each digit, the mean right-hand response time minus the mean left-hand response time (dRT) comes from correct answers at or after 100 ms, after answers more than 3 SD from the participant's mean are left out, again until none is. The main score is the slope of dRT on the digit (Fias and colleagues, 1996): negative values are the classic SNARC effect, the larger the digit, the faster the right hand against the left. The MARC effect (Nuerk, Iversen and Willmes, 2004) is the mean dRT of the even digits minus the odd digits; negative values mean even goes with right and odd with left. The dRT for each digit, the mean response time and its spread, and accuracy are also reported. Responses under 100 ms count as anticipations. The split-half reliability of the slope was about 0.70 with 20 answers per digit and hand in the lab (Cipora and Nuerk, 2013) and 0.43 with 10 online (Cipora and colleagues, 2019), so it suits group comparisons best.
Scores
- SNARC Slopescore
- Slope of the right-hand minus left-hand mean response time (dRT) on the digit, in ms per unit, from correct answers after trimming.
- Negative values are the classic effect: the larger the digit, the faster the right hand
- MARC Effectms
- Mean dRT of the even digits minus the odd digits.
- Negative values mean even goes with right and odd with left
- dRT by Digitms
- Right-hand minus left-hand mean response time for each digit.
- Usually falls as the digit grows
- Mean Correct Response Timems
- Mean response time of correct answers after trimming.
- Lower is faster
- Response Time Spreadms
- Standard deviation of the same response times.
- Informational
- Accuracy%
- Share of test trials answered with the key for the digit's parity.
- Higher is better
- Anticipationscount
- Answers under 100 ms from the digit's onset.
- Lower is better
- Missed Responsescount
- Trials with no key press within 2,000 ms.
- Lower is better
- Trimmed Answerscount
- Correct answers left out for lying more than 3 SD from the participant's mean.
- Informational
- Completed Trialstrials
- Trials shown in the scored run.
- Fewer than planned is flagged for review
- Planned Trialstrials
- Trials the run set out to show.
- Informational
Use and evidence
26 papers from 2021 to 2025 name this task in their title or abstract, down 4% compared with 2016 to 2020. That ranks it 313 of 395 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 2 |
| 2024 | 11 |
| 2023 | 5 |
| 2022 | 3 |
| 2021 | 5 |
| 2020 | 4 |
| 2019 | 4 |
| 2018 | 7 |
| 2017 | 6 |
| 2016 | 6 |
| 2015 | 2 |
| 2014 | 6 |
| 2013 | 5 |
| 2012 | 7 |
| 2011 | 2 |
| 2010 | 3 |
| 2009 | 6 |
| 2008 | 4 |
| 2007 | 8 |
| 2006 | 4 |
| 2005 | 1 |
| 2004 | 2 |
| 2003 | 0 |
| 2002 | 1 |
| 2001 | 2 |
| 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
- 1
- Papers on reliability or validity
- 4
- 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 0.14.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- Display
- On a dark panel: a blank for 500 ms and a cross for 300 ms, then one digit until a key or 2,000 ms.
- Digits
- 1, 2, 3, 4, 6, 7, 8 and 9: two odd and two even digits below 5 and above it, so parity and size are unrelated.
- Keys
- F with the left hand and J with the right. In two blocks F means odd and J even; in the other two the keys swap. The keys show under the panel in practice only.
- Blocks
- 4 blocks in the order A, B, B, A of the two key mappings, the first drawn for each session. Each shows each digit 10 times (standard; 6 to 12): 80 trials per block and 320 in all, in a seeded order with no digit twice in a row and at most 3 odd, even, small or large digits in a row.
- Practice
- 8 trials, each digit once, with feedback for 800 ms, before each block whose keys differ from the block before.
- Score
- For each digit, the mean right-hand minus left-hand response time (dRT) of correct answers at or after 100 ms, after answers more than 3 SD from the participant's mean are left out until none is; then the slope of dRT on the digit. Response times run from the screen frame that drew the digit.
As in Dehaene, Bossini and Giraux (1993), the size of a digit does not matter for the answer. The digits, the timing and the trimming follow Cipora and Nuerk (2013), and the order A, B, B, A spreads practice evenly over the two mappings. The slope has modest reliability for one person, so it suits group comparisons best. 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: snarc_test from the scored run, F or J within 2,000 ms (chance 50%; each key is right on half the trials of every block), graded from the saved digit and key mapping. 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. A run short of its planned trials, or too few correct answers to compute the SNARC slope, 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). 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.
No percentile. Scores and quality flags only.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Showings of each digit per block | 10 | 6 to 12 |
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 SNARC Parity Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Dehaene, Bossini and Giraux, 1993; Fias, Brysbaert, Geypens and d'Ydewalle, 1996), with the standard settings (showings of each digit per block: 10). The main score was SNARC slope (slope of the right-hand minus left-hand mean response time (dRT) on the digit, in ms per unit, from correct answers after trimming).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Dehaene, S., Bossini, S., & Giraux, P. (1993). The mental representation of parity and number magnitude. Journal of Experimental Psychology: General, 122(3), 371-396. https://doi.org/10.1037/0096-3445.122.3.371The parity task and the SNARC effect.
- Fias, W., Brysbaert, M., Geypens, F., & d'Ydewalle, G. (1996). The importance of magnitude information in numerical processing: Evidence from the SNARC effect. Mathematical Cognition, 2(1), 95-110. https://doi.org/10.1080/135467996387552The slope of dRT on the digit.
- Nuerk, H.-C., Iversen, W., & Willmes, K. (2004). Notational modulation of the SNARC and the MARC (linguistic markedness of response codes) effect. The Quarterly Journal of Experimental Psychology Section A, 57(5), 835-863. https://doi.org/10.1080/02724980343000512The MARC effect.
- Cipora, K., & Nuerk, H.-C. (2013). Is the SNARC effect related to the level of mathematics? No systematic relationship observed despite more power, more repetitions, and more direct assessment of arithmetic skill. Quarterly Journal of Experimental Psychology, 66(10), 1974-1991. https://doi.org/10.1080/17470218.2013.772215The digits, timing and trimming, and the reliability of the slope with 20 answers per digit and hand.
- Cipora, K., Soltanlou, M., Reips, U.-D., & Nuerk, H.-C. (2019). The SNARC and MARC effects measured online: Large-scale assessment methods in flexible cognitive effects. Behavior Research Methods, 51(4), 1676-1692. https://doi.org/10.3758/s13428-019-01213-5The run limits on the order, and both effects measured online.
Source papers
- Cipora K, Soltanlou M, Reips UD, Nuerk HC (2019). The SNARC and MARC effects measured online: large-scale assessment methods in flexible cognitive effects. Behavior Research Methods, 51(4):1676-1692.Paradigm source, Adults
Questions
How long does the SNARC Parity Task take?
About 9 to 11 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?
SNARC Slope, MARC Effect, dRT by Digit, Mean Correct Response Time, Response Time Spread, Accuracy, Anticipations, Missed Responses, Trimmed Answers, Completed Trials and Planned Trials. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the SNARC Parity Task used in research?
26 papers from 2021 to 2025 name it in their title or abstract, down 4% compared with 2016 to 2020. That ranks it 313 of 395 test families in the ConductCognition test census (use grade E). Source: ConductCognition test census 0.14.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the SNARC Parity Task have?
In the published research, 1 paper reports 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?
Showings of each digit per block (6 to 12). 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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