Episodic Memory
Word Stem Completion Task
Also called: word stem completion test, implicit memory test
Measure implicit memory: participants complete three-letter word stems with the first word that comes to mind, and words rated earlier come to mind more often than unshown words.
7-10 minUntimed
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
- 40
- Evidence grade
- C
- Registered clinical studies
- 4
What it measures
Measures implicit memory. Participants rate words for how much they like them, then complete three-letter word beginnings with the first word that comes to mind. The main score is priming: stems completed with a rated word minus stems completed with a word never shown. The words are in English.
Constructs
- Implicit memory
- Repetition priming
- Word retrieval
Research uses
- Implicit and explicit memory research
- Amnesia, aging and dementia research
- Within-study comparison of encoding conditions
How the paradigm works
Word stem completion measures implicit memory: a word seen earlier comes to mind more readily, even when the person is not trying to remember it. Amnesic patients who cannot recall a word list still complete its stems with the list words about as often as healthy people do (Graf, Squire and Mandler 1984). Participants first rate 24 English words for how much they like them, with nothing said about memory, and three fillers come before them and two after. A minute of true-or-false arithmetic follows by default (0 to 180 seconds as a setting).
More about the paradigm
Then a word task presented as a new one shows 48 three-letter stems, each followed by a line of the same length, and the participant types the first word that comes to mind that starts with those letters, as in Graf and Schacter (1985). Any word except a name is allowed, and a stem may be passed. Half the stems belong to the rated words and half to words never shown, which give the baseline. At least 10 common English words start with each stem, the task's word is not the most frequent of them, and no two words of the task share a stem. The session's seed decides which words are rated and orders both phases. Each stem has 15 seconds by default (10 to 30 as a setting), with a bar showing the time left. Three practice stems come first, with feedback on the form of the answer only. Two questions at the end ask whether the participant noticed, or tried to use, the rated words (Bowers and Schacter 1990).
The main score is priming: the share of rated words' stems completed with the rated word minus the share of baseline stems completed with their word. A plural counts as the word, and one spelling slip is accepted unless the typed word is another English word. The words are English; sessions run in other languages are flagged for review. Scores support research and do not diagnose.
Scores
- Priming Effect%
- Share of rated words' stems completed with the rated word minus the share of baseline stems completed with their word.
- Positive means rated words came to mind more often than unshown words
- Rated-Word Completions%
- Share of rated words' stems completed with the rated word.
- Compare with the baseline rate
- Baseline Completions%
- Share of stems of words never shown that were completed with that word.
- How often the words come to mind without study
- Stems Completed%
- Share of stems answered with a word that starts with the stem.
- Below 50% is invalid
- Answers Off the Stemcount
- Typed answers that do not start with the stem.
- Context for the completion rate
- Stems Passedcount
- Stems passed with nothing typed.
- Context for the completion rate
- Time-outscount
- Stems with no answer when the time ran out.
- Context for the completion rate
- Median Completion Timems
- Median time from a stem's appearance to the answer on completed stems, leaving out answers under 100 ms.
- Context for the completions
- Noticed Rated Words0/1
- 1 when the participant says they noticed that some stems fit rated words.
- Describes test awareness
- Tried Rated Words0/1
- 1 when the participant says they tried to complete stems with rated words.
- 1 is flagged for review
- Words Ratedcount
- Liking ratings given, fillers included.
- Context for the study phase
- Median Rating Timems
- Median time to rate a word.
- Under 200 ms is flagged for review
- Stems Presenteditems
- Stems shown in the scored run.
- Fewer than 90% of those planned is invalid
- Stems Planneditems
- Stems the session set out to show.
- 40, 48 or 60
- Answers Under 100 mscount
- Answers submitted within 100 ms of the stem.
- Expected to be 0
- Paste Attemptscount
- Blocked attempts to paste or drop text into the answer box.
- Any is flagged for review
- Delayseconds
- Seconds of arithmetic between the ratings and the stems.
- Setting context
Use and evidence
40 papers from 2021 to 2025 name this task in their title or abstract, down 27% compared with 2016 to 2020. That ranks it 271 of 395 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 12 |
| 2024 | 7 |
| 2023 | 3 |
| 2022 | 7 |
| 2021 | 11 |
| 2020 | 13 |
| 2019 | 9 |
| 2018 | 10 |
| 2017 | 14 |
| 2016 | 9 |
| 2015 | 19 |
| 2014 | 18 |
| 2013 | 13 |
| 2012 | 15 |
| 2011 | 16 |
| 2010 | 25 |
| 2009 | 22 |
| 2008 | 20 |
| 2007 | 20 |
| 2006 | 15 |
| 2005 | 28 |
| 2004 | 24 |
| 2003 | 26 |
| 2002 | 27 |
| 2001 | 26 |
| 2000 | 28 |
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
- 1
- Papers on reliability or validity
- 26
- Registered clinical studies using it as an outcome
- 4
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.
- Words
- 60 English words chosen by rule. At least 10 common English words start with each word's first three letters (its stem), the word is not the most frequent of them, and no two words of the task share a stem.
- Ratings
- 24 words by default, or 20 or 30 as a setting, each rated from 1 to 5 for how much the participant likes it, without a time limit. 3 fillers come first and 2 last. Nothing is said about memory.
- Delay
- 60 seconds of true-or-false arithmetic by default, 0 to 180 as a setting.
- Stems
- Presented as a new word task: the stems of the rated words and of as many words never shown, in the session's seeded order with no more than 3 of one kind in a row, 15 seconds each by default (10 to 30 as a setting), with a bar showing the time left.
- Answer
- The first word that comes to mind, typed with autocorrect off and submitted with Enter or a button; an empty answer passes. A plural counts as the word, and one spelling slip is accepted in a word of 4 or more letters unless the typed word is another English word.
- Practice
- 3 stems outside the set, each followed by feedback on the form of the answer only.
- Questions
- Two questions at the end ask whether the participant noticed, or tried to use, the rated words.
The words were chosen for this task by rule from open word lists; no published word or stem list is used. The words are English; sessions run in other languages are flagged for review.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: stem_completion_test from the scored run, one typed word per stem within its time limit, with the liking ratings and the two closing questions from the same run. Any word that starts with the stem is a valid answer, so there is no chance level and accuracy is not judged. Fewer than 90% of the planned stems presented invalidates, and so do valid completions on fewer than half the stems. Typed answers under 200 ms on at least half of 4 or more answers invalidate. A participant who says they tried to use the rated words is flagged and the percentile withheld. Ratings with a median time under 200 ms, a blocked paste, or a session run in another language are flagged for review. A hidden tab withholds the percentile.
Why these rules
There is no correct option to compare with chance, so accuracy is not judged against chance. A score over a much shorter session cannot be compared with a full one, and with few stems completed the priming score has no base. The measure is implicit memory: a participant who deliberately recalls the rated words turns the test into cued recall (Graf, Squire and Mandler 1984; Bowers and Schacter 1990), so that answer is flagged. Words rated faster than a visual reaction were probably not read. A blocked paste can mean answers were being looked up. An answer under 200 ms is faster than a simple visual reaction, so it cannot reflect the item. Following response-time effort screening for untimed tests (Wise and Kong 2005), the session is invalid only when at least half the answers are that fast. The word lists are English. A session run in another language shows English words to a participant who may not read English fluently, so it is flagged for review. 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 |
|---|---|---|
| Words rated | 24 words (48 stems, standard) | 20 words (40 stems), 24 words (48 stems, standard), 30 words (60 stems) |
| Time per stem (seconds) | 15 | 10 to 30 |
| Delay before the stems (seconds) | 60 | 0 to 180 |
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
- Instructions and screens: English, Spanish, French, German, Italian, Portuguese (Brazil), Chinese (Simplified) and Japanese. Words and sentences: English.
- 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 Word Stem Completion Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Graf, Squire & Mandler, 1984; Graf & Schacter, 1985), with the standard settings (words rated: 24 words (48 stems, standard); time per stem (seconds): 15; delay before the stems (seconds): 60). The main score was priming effect (share of rated words' stems completed with the rated word minus the share of baseline stems completed with their word).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Graf, P., & Schacter, D. L. (1985). Implicit and explicit memory for new associations in normal and amnesic subjects. Journal of Experimental Psychology: Learning, Memory, and Cognition, 11(3), 501-518. https://doi.org/10.1037/0278-7393.11.3.501
- Graf, P., Squire, L. R., & Mandler, G. (1984). The information that amnesic patients do not forget. Journal of Experimental Psychology: Learning, Memory, and Cognition, 10(1), 164-178. https://doi.org/10.1037/0278-7393.10.1.164
- Graf, P., Mandler, G., & Haden, P. E. (1982). Simulating amnesic symptoms in normal subjects. Science, 218(4578), 1243-1244. https://doi.org/10.1126/science.7146909
- Bowers, J. S., & Schacter, D. L. (1990). Implicit memory and test awareness. Journal of Experimental Psychology: Learning, Memory, and Cognition, 16(3), 404-416. https://doi.org/10.1037/0278-7393.16.3.404
Source papers
- Graf P, Schacter DL (1985). Implicit and explicit memory for new associations in normal and amnesic subjects. Journal of Experimental Psychology: Learning, Memory, and Cognition, 11(3):501-518.Paradigm source, Young adults and amnesic patients
- Graf P, Squire LR, Mandler G (1984). The information that amnesic patients do not forget. Journal of Experimental Psychology: Learning, Memory, and Cognition, 10(1):164-178.Paradigm source, Adults and amnesic patients
Questions
How long does the Word Stem Completion Task take?
About 7 to 10 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?
Priming Effect, Rated-Word Completions, Baseline Completions, Stems Completed, Answers Off the Stem, Stems Passed, Time-outs, Median Completion Time, Noticed Rated Words, Tried Rated Words, Words Rated, Median Rating Time, Stems Presented, Stems Planned, Answers Under 100 ms, Paste Attempts and Delay. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Word Stem Completion Task used in research?
40 papers from 2021 to 2025 name it in their title or abstract, down 27% compared with 2016 to 2020. That ranks it 271 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 Word Stem Completion Task have?
In the published research, 1 paper reports its test-retest reliability and 4 registered clinical studies use it as an outcome (evidence grade C in the ConductCognition test census).
Does it report a percentile?
No. Scores and quality flags only.
Which settings can a researcher change?
Words rated (20 words (40 stems), 24 words (48 stems, standard), 30 words (60 stems)), time per stem (seconds) (10 to 30) and delay before the stems (seconds) (0 to 180). Settings can be changed on yearly plans; free and pay-as-you-go studies use the standard settings.
Which languages can participants use?
The instructions and screens are in English, Spanish, French, German, Italian, Portuguese (Brazil), Chinese (Simplified) and Japanese. The words and sentences stay in English, so sessions in other languages are flagged for review. 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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