Episodic Memory
Spacing Effect Task
Also called: distributed practice effect, massed versus spaced repetition, lag effect
Words shown twice in a row or spread apart in one list, then free recall: repetitions spread apart are remembered better.
6-9 minUntimed
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
- 26
- Evidence grade
- D
- Registered clinical studies
- 0
What it measures
Measures the memory benefit of spacing. In one list, some words are shown once, some twice in a row and some twice with other words between; participants then type the words they remember.
Constructs
- Distributed practice
- Repetition
- Free recall
- Episodic memory
Research uses
- Learning and memory research on distributed practice
- Aging and memory research
- Education research
How the paradigm works
The Spacing Effect Task measures the memory benefit of spacing: a word studied twice is remembered better when its two showings are spread apart than when they come one right after the other. It is the mixed-list free recall procedure of Madigan (1969) and Glenberg (1977). One list of 30 words is shown one word every 2 seconds: 10 words once, 10 twice in a row (massed) and 10 twice with 6 to 15 other words between the two showings (spaced), in an order drawn for each session. Two buffer words open the list and two close it, shown once and not scored. After 30 seconds of true-or-false arithmetic, participants type every word they remember, in any order, on a visible timer. A practice list of 4 words comes first.
More about the paradigm
The main score is the spacing benefit: the share of spaced words recalled minus the share of massed words recalled. Recall in each condition and the difference between massed words and words shown once are also reported. Across 271 comparisons in the review of Cepeda and colleagues (2006), spaced study led to better recall than massed study (47.3% against 36.7%), and the benefit held at retention intervals under a minute. The words are concrete nouns written for this task in each of the eight app languages; each session deals them to the conditions at random, so across sessions every word serves in every condition. With 10 words in each condition, one person's difference is noisy and is best used to compare groups. Scores support research and do not diagnose.
Scores
- Spacing Benefit%
- Share of spaced words recalled minus share of massed words recalled.
- Higher means more benefit from spacing
- Spaced Words Recalled%
- Share of the 10 words shown twice with other words between that were recalled.
- Higher is better
- Massed Words Recalled%
- Share of the 10 words shown twice in a row that were recalled.
- Higher is better
- Once Words Recalled%
- Share of the 10 words shown once that were recalled.
- Higher is better
- Massed Minus Once%
- Share of massed words recalled minus share of words shown once recalled.
- The benefit of a second showing in a row
- Words Recalledcount
- List words recalled, of 30; buffer words are left out.
- Higher is better
- Intrusionscount
- Typed entries that name no word shown.
- Lower is better
- Mean Spaced Lagitems
- Mean number of other showings between the two showings of a spaced word.
- Informational
- Delay Arithmetic Accuracy%
- Share of the true-or-false arithmetic answered correctly in the delay.
- Shows the delay task was done
Use and evidence
26 papers from 2021 to 2025 name this task in their title or abstract, up 8% compared with 2016 to 2020. That ranks it 381 of 495 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 7 |
| 2024 | 3 |
| 2023 | 2 |
| 2022 | 6 |
| 2021 | 8 |
| 2020 | 4 |
| 2019 | 4 |
| 2018 | 4 |
| 2017 | 7 |
| 2016 | 5 |
| 2015 | 7 |
| 2014 | 11 |
| 2013 | 4 |
| 2012 | 3 |
| 2011 | 2 |
| 2010 | 2 |
| 2009 | 2 |
| 2008 | 4 |
| 2007 | 0 |
| 2006 | 1 |
| 2005 | 0 |
| 2004 | 0 |
| 2003 | 1 |
| 2002 | 0 |
| 2001 | 0 |
| 2000 | 1 |
Use grade E
Fewer than 30 papers from 2021 to 2025.
Evidence grade D
Little published measurement evidence found.
- Papers on test-retest reliability
- 0
- Papers on reliability or validity
- 2
- Registered clinical studies using it as an outcome
- 0
Note on the counts: counted with specific phrases, since 'spacing effect' also names plant and row spacing; undercounts.
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 0.22.0, counted 2 November 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- List
- 30 concrete nouns: 10 shown once, 10 twice in a row (massed) and 10 twice with 6 to 15 other words between the two showings (spaced), in an order drawn for each session. 2 buffer words open the list and 2 close it, shown once and not scored.
- Timing
- One showing every 2 seconds: each word for 1,750 ms and then a 250 ms blank, switched on animation frames; 54 showings in all.
- Delay
- 30 seconds (standard; 0 to 120) of true-or-false arithmetic.
- Recall
- Typed one word at a time, in any order, for up to 180 seconds (standard; 60 to 300) on a visible timer, with a Done button. A word shown twice is typed once.
- Spelling
- Case, accents and punctuation are ignored, and plurals and other spellings count. In languages written in letters, one wrong, missing, extra or swapped letter is accepted in words of 4 or more letters unless the answer is another word of the language. In Japanese, kanji, hiragana and katakana count; in Chinese, simplified and traditional characters.
- Scores
- The spacing benefit: the share of spaced words recalled minus the share of massed words recalled (Madigan 1969; Cepeda et al. 2006). Recall in each condition and massed minus once are also reported.
- Practice
- A list of 4 words (one spaced, one massed, two shown once) with untimed recall, then the number typed.
The words were written for this task in eight languages; no published word list is used.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: the spacing_effect_recall row of the scored run (practice excluded), typed recall of the list, with the delay arithmetic of the same run. Typed recall has no chance level and no response is required, so accuracy is not judged against chance. Recalling no list word is flagged. Typing more words from outside the list than list words, with at least 6 of them, is flagged. Blocked paste attempts are flagged. No arithmetic answered in the delay, or delay arithmetic at or below chance over at least 10 answers, is flagged. A hidden tab withholds the percentile.
Why these rules
Recall has no options to guess between, and recalling nothing can be a real result, so it is flagged for review rather than invalidated. Many words from outside the list suggest the instructions were not followed, and pasting could bring in words from elsewhere. The arithmetic fills the delay so the last words are not rehearsed. A hidden tab lets the study, delay or response timers run without the participant, so a percentile is withheld after one.
No percentile. Scores and quality flags only.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Arithmetic before the recall (seconds) | 30 | 0 to 120 |
| Recall time (seconds) | 180 | 60 to 300 |
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
- Untimed test: runs on desktops, laptops, tablets and phones. 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 Spacing Effect Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Madigan, 1969; Cepeda, Pashler, Vul, Wixted & Rohrer, 2006), with the standard settings (arithmetic before the recall (seconds): 30; recall time (seconds): 180). The main score was spacing benefit (share of spaced words recalled minus share of massed words recalled).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Madigan, S. A. (1969). Intraserial repetition and coding processes in free recall. Journal of Verbal Learning and Verbal Behavior, 8(6), 828-835. https://doi.org/10.1016/S0022-5371(69)80050-2The mixed list of words shown once and twice at different lags.
- Glenberg, A. M. (1977). Influences of retrieval processes on the spacing effect in free recall. Journal of Experimental Psychology: Human Learning and Memory, 3(3), 282-294. https://doi.org/10.1037/0278-7393.3.3.282
- Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin, 132(3), 354-380. https://doi.org/10.1037/0033-2909.132.3.354Spacing and lag effects across 317 experiments.
- Kahana, M. J., & Howard, M. W. (2005). Spacing and lag effects in free recall of pure lists. Psychonomic Bulletin & Review, 12(1), 159-164. https://doi.org/10.3758/BF03196362
Source papers
- Cepeda NJ, Pashler H, Vul E, Wixted JT, Rohrer D (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin, 132(3):354-380.Paradigm source
- Madigan SA (1969). Intraserial repetition and coding processes in free recall. Journal of Verbal Learning and Verbal Behavior, 8(6):828-835.Paradigm source
Questions
How long does the Spacing Effect Task take?
About 6 to 9 minutes, as listed in the test library.
What device does a participant need?
Untimed test: runs on desktops, laptops, tablets and phones. The browser must be Chrome, Edge, Firefox or Safari.
What scores does it produce?
Spacing Benefit, Spaced Words Recalled, Massed Words Recalled, Once Words Recalled, Massed Minus Once, Words Recalled, Intrusions, Mean Spaced Lag and Delay Arithmetic Accuracy. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Spacing Effect Task used in research?
26 papers from 2021 to 2025 name it in their title or abstract, up 8% compared with 2016 to 2020. That ranks it 381 of 495 test families in the ConductCognition test census (use grade E). Source: ConductCognition test census 0.22.0, counted 2 November 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Spacing Effect 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?
Arithmetic before the recall (seconds) (0 to 120) and recall time (seconds) (60 to 300). 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, with its words in the same language. 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.