Processing Speed
Pattern and Letter Comparison
Also called: pattern comparison task, letter comparison task, perceptual comparison task
Measure perceptual speed: how many pairs of line patterns and letter strings a person can judge same or different against the clock.
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
- 70
- Evidence grade
- C
- Registered clinical studies
- 146
What it measures
A timed measure of perceptual speed. Two line patterns or two strings of consonants appear side by side, and the person answers same or different as fast as they can without many errors. Timed blocks of patterns and letters take turns. The score is right answers minus wrong answers.
Constructs
- Perceptual speed
- Processing speed
Research uses
- Aging and cognition research
- Processing speed research
- Within-study group comparison
How the paradigm works
Pattern and Letter Comparison measures perceptual speed: how fast a person can compare two simple things. Salthouse and Babcock (1991) used pairs of line patterns and pairs of letter strings, judged same or different against the clock, to study why working memory changes across adulthood, and Salthouse (1996) placed speed of this kind at the center of a theory of cognitive aging. In this version two patterns of connected line segments, or two strings of consonants, stand side by side, 3, 6 or 9 segments or letters long. Half the pairs are the same, and a different pair changes one segment or one letter. The person presses F for same or J for different as fast as they can without many errors, and the next pair follows at once. Blocks of patterns and letters take turns, each with a time bar, 30 seconds each as standard. The primary score is net correct, right answers minus wrong answers, so guessing faster gains nothing. Answers under 100 ms count as neither right nor wrong. Scores support research and do not diagnose.
Scores
- Net Correctscore
- Right answers minus wrong answers across all blocks.
- Higher means faster accurate comparing
- Net Correct, Patternsscore
- Right minus wrong answers in the pattern blocks.
- Higher means faster accurate comparing
- Net Correct, Lettersscore
- Right minus wrong answers in the letter blocks.
- Higher means faster accurate comparing
- Net Correct at Length 3score
- Right minus wrong answers on pairs of 3 segments or letters.
- Higher means faster accurate comparing
- Net Correct at Length 6score
- Right minus wrong answers on pairs of 6 segments or letters.
- Higher means faster accurate comparing
- Net Correct at Length 9score
- Right minus wrong answers on pairs of 9 segments or letters.
- Higher means faster accurate comparing
- Median Correct Response Timems
- Median time from the pair to the key, over right answers.
- Lower is faster
- Accuracy%
- Right answers as a share of right and wrong answers.
- Under 70% invalidates the session
- 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 Pairsitems
- Pairs answered with a key, anticipations included.
- Under 10 a minute invalidates the session
- Anticipationscount
- Answers under 100 ms, which count as neither right nor wrong.
- Lower is better
- Completed Blockscount
- Blocks with at least one pair shown.
- Fewer than planned invalidates the session
- Planned Blockscount
- Blocks in the session's plan.
- Set by the settings
- Test Timeseconds
- The time limits of the blocks shown, added together.
- Set by the settings
Use and evidence
70 papers from 2021 to 2025 name this task in their title or abstract, up 119% compared with 2016 to 2020. That ranks it 223 of 395 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 18 |
| 2024 | 17 |
| 2023 | 18 |
| 2022 | 9 |
| 2021 | 8 |
| 2020 | 10 |
| 2019 | 9 |
| 2018 | 6 |
| 2017 | 3 |
| 2016 | 4 |
| 2015 | 3 |
| 2014 | 6 |
| 2013 | 2 |
| 2012 | 1 |
| 2011 | 0 |
| 2010 | 0 |
| 2009 | 1 |
| 2008 | 1 |
| 2007 | 2 |
| 2006 | 0 |
| 2005 | 1 |
| 2004 | 2 |
| 2003 | 0 |
| 2002 | 0 |
| 2001 | 0 |
| 2000 | 1 |
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
- 7
- Papers on reliability or validity
- 23
- Registered clinical studies using it as an outcome
- 146
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.
- Trial
- Two line patterns or two strings of consonants side by side, until a key is pressed or the block's time runs out. The next pair follows at once.
- Pairs
- Half the pairs are the same. A different pair changes one segment or one letter, at any place.
- Lengths
- 3, 6 or 9 segments or letters. Every 6 pairs hold each length with each answer once.
- Line patterns
- Connected line segments on a grid of 4 by 4 dots, drawn for each session from its seed.
- Letters
- 20 consonants without repeats, filtered so a string spells nothing. Letters are drawn as shapes in every language.
- Blocks
- 4 blocks of 30 seconds (standard; 2, 4 or 6 blocks of 20 to 60 seconds). Patterns and letters take turns, and each block shows a time bar.
- Keys
- F for same and J for different, shown on screen and read without case.
- Practice
- 6 pairs of each kind with feedback and no time limit.
- Score
- Right answers minus wrong answers. Answers under 100 ms count as neither, and a pair cut off by the time limit counts for nothing.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: pattern_comparison_test from the scored run, same or different key presses in timed blocks. Chance is 1 in 2, and the correct keys are balanced. A pair cut off when a block'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 blocks 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 pair. The two sides are always easy to tell apart with time, so accuracy is not what this test measures: errors are few in a person who is comparing, 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 about a third of the rate in a study of adults (Draheim, Tshukara and Engle 2024), too few to show speed, and net correct is only comparable when every planned block ran.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Block length (seconds) | 30 | 20 to 60 |
| Blocks | 4 | 2, 4, 6 |
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 Pattern and Letter Comparison task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Salthouse & Babcock, 1991), with the standard settings (block length (seconds): 30; blocks: 4). The main score was net correct (right answers minus wrong answers across all blocks).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Salthouse, T. A., & Babcock, R. L. (1991). Decomposing adult age differences in working memory. Developmental Psychology, 27(5), 763-776. https://doi.org/10.1037/0012-1649.27.5.763The pattern and letter comparison measures of perceptual speed.
- Salthouse, T. A. (1996). The processing-speed theory of adult age differences in cognition. Psychological Review, 103(3), 403-428. https://doi.org/10.1037/0033-295X.103.3.403Why speed of simple comparing matters for cognition across adulthood.
- Salthouse, T. A. (2004). What and when of cognitive aging. Current Directions in Psychological Science, 13(4), 140-144. https://doi.org/10.1111/j.0963-7214.2004.00293.x
- Draheim, C., Tshukara, J. S., & Engle, R. W. (2024). Behavior Research Methods, 56(3), 2135-2157. https://doi.org/10.3758/s13428-023-02140-2Computer versions with 3, 6 or 9 letters or segments, 30 second blocks, and right minus wrong scoring.
Source papers
- Salthouse TA, Babcock RL (1991). Decomposing adult age differences in working memory. Developmental Psychology, 27(5):763-776.Paradigm source, Adults
Questions
How long does the Pattern and Letter Comparison 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, Net Correct, Patterns, Net Correct, Letters, Net Correct at Length 3, Net Correct at Length 6, Net Correct at Length 9, Median Correct Response Time, Accuracy, Right Answers, Wrong Answers, Answered Pairs, Anticipations, Completed Blocks, Planned Blocks and Test Time. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Pattern and Letter Comparison used in research?
70 papers from 2021 to 2025 name it in their title or abstract, up 119% compared with 2016 to 2020. That ranks it 223 of 395 test families in the ConductCognition test census (use grade D). Source: ConductCognition test census 0.14.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Pattern and Letter Comparison have?
In the published research, 7 papers report its test-retest reliability and 146 registered clinical studies use it as an outcome (evidence grade C in the ConductCognition test census).
Which settings can a researcher change?
Block length (seconds) (20 to 60) and blocks (2, 4, 6). 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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