ConductCognition

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    Evidence

    1. Verbal Fluency TestGradeA
    2. Stroop Color-Word TestGradeA
    3. Trail Making TestGradeA
    4. N-Back TaskGradeA
    5. Go/No-Go TaskGradeA
    6. Digit Span TestGradeA
    7. Symbol Coding TestGradeA
    8. Verbal Learning TestGradeA
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    • Older Adult Executive SpeedGradeA20 min
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    • Motor and AttentionGradeA−29 min
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    • Food Choice and Self-ControlGradeA−29 min
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    16,361Registered studies name a cognitive test in an outcome measure11,688 name a test you can run hereExplore the studies
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  1. Home
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  5. /N-Back Task

Clinical trials data

N-Back Task in clinical trials: 790 registered studies

Every registered study on ClinicalTrials.gov that names the N-Back Task in an outcome measure: the conditions it is used in, how often it is a primary outcome, the tests it is named with, and how large the studies are.

Registered studies name it in an outcome measure
790
Name it in a primary outcome, 48%
381 of 790
Against similar tests
Of studies started 2021 to 2025 name it, against 5.0% in 2016 to 2020
4.8%
By year
Median participants per study
60
By phase
Try the 1-Back TaskTry the 2-Back Task

The conditions it is used in

Each study counted once in each condition group it falls in.

  1. Depression and bipolar disorder79 studies, 28 as a primary outcome

  2. Aging, frailty and exercise68 studies, 39 as a primary outcome

  3. Substance use and addiction68 studies, 37 as a primary outcome

  4. Schizophrenia and psychosis66 studies, 32 as a primary outcome

  5. Healthy volunteers51 studies, 26 as a primary outcome

  6. Sleep and sleep disorders51 studies, 20 as a primary outcome

  7. Dementia and Alzheimer's44 studies, 21 as a primary outcome

  8. Mild cognitive impairment42 studies, 18 as a primary outcome

  9. Obesity and diabetes33 studies, 14 as a primary outcome

  10. Anxiety, PTSD and OCD31 studies, 12 as a primary outcome

  11. Pain and fatigue31 studies, 12 as a primary outcome

  12. ADHD30 studies, 19 as a primary outcome

  13. Brain injury and concussion26 studies, 14 as a primary outcome

  14. Stroke22 studies, 13 as a primary outcome

  15. Cardiovascular disease20 studies, 12 as a primary outcome

  16. Cancer19 studies, 9 as a primary outcome

  17. Cognitive impairment and decline16 studies, 10 as a primary outcome

  18. Parkinson's disease13 studies, 4 as a primary outcome

  19. Multiple sclerosis6 studies, 2 as a primary outcome

  20. Autism5 studies, 4 as a primary outcome

  21. Delirium, surgery and intensive care5 studies, 1 as a primary outcome

  22. COVID-19 and long COVID4 studies, 2 as a primary outcome

  23. Hearing loss3 studies, 2 as a primary outcome

  24. Epilepsy3 studies, 1 as a primary outcome

  25. Lung disease3 studies, 2 as a primary outcome

  26. Huntington's disease1 study, 1 as a primary outcome

  27. Other conditions172 studies, 84 as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

How often it is a primary outcome

The N-Back Task is a primary outcome in 48% of its studies. Across the 10 working memory tests with a page here, the median is 45%.

  1. Sternberg Memory Scanning50% of 38 studies

  2. Operation Span50% of 24 studies

  3. Mental Rotation48% of 64 studies

  4. N-Back Task48% of 790 studies

  5. Spatial Working Memory46% of 78 studies

  6. Letter-Number Sequencing Task43% of 184 studies

  7. Corsi Block-Tapping Test43% of 181 studies

  8. Digit Span Test37% of 1,629 studies

  9. Reading Span Task36% of 22 studies

  10. Size Order Memory Test35% of 162 studies

Studies by start year

4.8% of the registered studies that started in 2021 to 2025 name it, against 5.0% of those that started in 2016 to 2020. 2026 is partly planned starts.
02000: 0 studies, 0 with a test as a primary outcome20002001: 0 studies, 0 with a test as a primary outcome2002: 2 studies, 1 with a test as a primary outcome2003: 2 studies, 1 with a test as a primary outcome2004: 0 studies, 0 with a test as a primary outcome2005: 4 studies, 3 with a test as a primary outcome20052006: 3 studies, 1 with a test as a primary outcome2007: 10 studies, 7 with a test as a primary outcome2008: 10 studies, 2 with a test as a primary outcome2009: 5 studies, 4 with a test as a primary outcome2010: 11 studies, 4 with a test as a primary outcome20102011: 20 studies, 8 with a test as a primary outcome2012: 14 studies, 6 with a test as a primary outcome2013: 23 studies, 13 with a test as a primary outcome2014: 25 studies, 14 with a test as a primary outcome2015: 25 studies, 13 with a test as a primary outcome20152016: 32 studies, 19 with a test as a primary outcome2017: 51 studies, 24 with a test as a primary outcome2018: 54 studies, 30 with a test as a primary outcome2019: 59 studies, 24 with a test as a primary outcome2020: 30 studies, 14 with a test as a primary outcome20202021: 70 studies, 35 with a test as a primary outcome2022: 62 studies, 34 with a test as a primary outcome2023: 71 studies, 32 with a test as a primary outcome2024: 69 studies, 35 with a test as a primary outcome2025: 67 studies, 29 with a test as a primary outcome20252026: 68 studies, 25 with a test as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

Show as a table
Registered studies by start year
Start yearStudiesA test as a primary outcome
200000
200100
200221
200321
200400
200543
200631
2007107
2008102
200954
2010114
2011208
2012146
20132313
20142514
20152513
20163219
20175124
20185430
20195924
20203014
20217035
20226234
20237132
20246935
20256729
20266825

Phases and study sizes

By phase

  • Early phase 110 studies, 8 as a primary outcome
  • Phase 140 studies, 15 as a primary outcome
  • Phase 1/212 studies, 6 as a primary outcome
  • Phase 259 studies, 27 as a primary outcome
  • Phase 2/36 studies, 4 as a primary outcome
  • Phase 312 studies, 5 as a primary outcome
  • Phase 428 studies, 13 as a primary outcome
  • Not applicable557 studies, 263 as a primary outcome
  • Observational66 studies, 40 as a primary outcome

Participants per study

102050100200500
  • Early phase 146 median, 27 to 68
  • Phase 136 median, 24 to 75
  • Phase 1/227 median, 19 to 66
  • Phase 255 median, 20 to 97
  • Phase 3158 median, 77 to 365
  • Phase 463 median, 40 to 100
  • Not applicable60 median, 32 to 100
  • Observational100 median, 47 to 207
Participants per study. The bar spans the middle half of the studies in each phase, the mark is the median, and the axis is logarithmic. Phases with fewer than 10 studies that give a size are left out.
Show as a table
Participants per study that names the N-Back Task, by phase
PhaseStudies with a sizeMedianMiddle half
Early phase 1104627 to 68
Phase 1383624 to 75
Phase 1/2122719 to 66
Phase 2565520 to 97
Phase 31215877 to 365
Phase 4286340 to 100
Not applicable5486032 to 100
Observational6410047 to 207

When trials measure it

Half of the primary outcomes that name the N-Back Task are measured within 4 weeks of the start, and the middle half from the first day to 12 weeks. 350 primary outcomes give a duration.

Latest time point of each outcome

  • Within a day178 outcomes, 102 as a primary outcome
  • Up to 4 weeks196 outcomes, 97 as a primary outcome
  • 1 to 3 months192 outcomes, 81 as a primary outcome
  • 3 to 6 months84 outcomes, 31 as a primary outcome
  • 6 to 12 months57 outcomes, 24 as a primary outcome
  • 1 to 2 years13 outcomes, 7 as a primary outcome
  • Over 2 years12 outcomes, 8 as a primary outcome
  • No duration given57 outcomes, 31 as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

732 of the 789 outcome measures give a duration. A single visit counts as within a day.

Status, results, interventions and countries

Status

  • Recruiting134 studies, 48 as a primary outcome
  • Not yet recruiting44 studies, 20 as a primary outcome
  • Active, not recruiting20 studies, 16 as a primary outcome
  • Completed435 studies, 229 as a primary outcome
  • Stopped early50 studies, 22 as a primary outcome
  • Status unknown107 studies, 46 as a primary outcome

What they test

  • Behavioral212 studies, 108 as a primary outcome
  • Drug179 studies, 82 as a primary outcome
  • Device189 studies, 85 as a primary outcome
  • Dietary supplement64 studies, 25 as a primary outcome
  • Procedure18 studies, 9 as a primary outcome
  • Diagnostic test6 studies, 2 as a primary outcome
  • Biological6 studies, 3 as a primary outcome
  • Radiation6 studies, 4 as a primary outcome
  • Combination product5 studies, 2 as a primary outcome
  • Other199 studies, 96 as a primary outcome
  • None given33 studies, 20 as a primary outcome

Intervention types as registered. A study can list several; observational studies often list none.

Where their sites are

  • United States288 studies, 161 as a primary outcome
  • Canada71 studies, 29 as a primary outcome
  • United Kingdom55 studies, 18 as a primary outcome
  • China54 studies, 22 as a primary outcome
  • Germany37 studies, 19 as a primary outcome
  • France28 studies, 11 as a primary outcome
  • Hong Kong27 studies, 8 as a primary outcome
  • Spain25 studies, 8 as a primary outcome
  • Switzerland24 studies, 7 as a primary outcome
  • Netherlands22 studies, 9 as a primary outcome
  • Türkiye22 studies, 14 as a primary outcome
  • Taiwan18 studies, 6 as a primary outcome

42 countries in all. A study with sites in several counts in each; 39 list no site.

Reported results

Completed studies with results posted on ClinicalTrials.gov, a results paper the registry links to the study, or both.

Completed studies that name the N-Back Task: 212 of 435, 49%

Every completed study with a cognitive outcome: 3,626 of 7,953, 46%

Completed studies that name the N-Back Task and every completed study, by how they reported results
ResultsCompleted studies that name the N-Back TaskEvery completed study
Results on ClinicalTrials.gov and a paper32, 7%776, 10%
Results on ClinicalTrials.gov only61, 14%1,139, 14%
A results paper only119, 27%1,711, 22%
Neither223, 51%4,327, 54%

Tests named in the same studies

The library tests that studies naming the N-Back Task name most often beside it.
  1. 1

    Stroop Color-Word Test128 studies, 56 as a primary outcome

  2. 2

    Trail Making Test109 studies, 34 as a primary outcome

  3. 3

    Digit Span Test94 studies, 32 as a primary outcome

  4. 4

    Go/No-Go Task87 studies, 32 as a primary outcome

  5. 5

    Verbal Fluency83 studies, 36 as a primary outcome

  6. 6

    Verbal Learning82 studies, 40 as a primary outcome

  7. 7

    Symbol Coding77 studies, 29 as a primary outcome

  8. 8

    Continuous Performance Test65 studies, 25 as a primary outcome

  9. 9

    Eriksen Flanker Task55 studies, 32 as a primary outcome

  10. 10

    Psychomotor Vigilance Task46 studies, 26 as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

Compared over time

Studies per start year for the N-Back Task and the tests named with it most. Add or remove tests to compare.
N-Back Task787 studies, 2000 to 2026
01252502000201020202026
Stroop Color-Word Test1,922 studies, 2000 to 2026
01252502000201020202026
Trail Making Test2,281 studies, 2000 to 2026
01252502000201020202026
Digit Span Test1,619 studies, 2000 to 2026
01252502000201020202026

The panel's testThe other tests chosenEvery panel has the same scale. 2026 is partly planned starts.

Show as a table
Registered studies per start year that name each test
Start yearN-Back TaskStroop Color-Word TestTrail Making TestDigit Span Test
20000323
20010302
20022531
20032284
200408104
2005411147
200636144
200710132114
200810151719
20095162922
201011293237
201120314726
201214324436
201323426044
201425646649
201525678579
2016328510369
2017517912282
20185410311785
201959119155110
2020309912290
202170151172122
202262168188121
202371198228164
202469182211141
202567198210147
202668193201137

Explore the 790 studies

Filter by condition, phase, sponsor, status, country, intervention, outcome list, size and start year. Each study links to its record on ClinicalTrials.gov.
TestThe N-Back Task

790 studies match. 381 name the N-Back Task in a primary outcome. Median size 60 participants. Median time to the primary outcome: 4 weeks.

Loading 790 studies; the filters turn on when they arrive.

By start year
0204060802000: 0 studies, 0 naming the N-Back Task in a primary outcome20002001: 0 studies, 0 naming the N-Back Task in a primary outcome2002: 2 studies, 1 naming the N-Back Task in a primary outcome2003: 2 studies, 1 naming the N-Back Task in a primary outcome2004: 0 studies, 0 naming the N-Back Task in a primary outcome2005: 4 studies, 3 naming the N-Back Task in a primary outcome20052006: 3 studies, 1 naming the N-Back Task in a primary outcome2007: 10 studies, 7 naming the N-Back Task in a primary outcome2008: 10 studies, 2 naming the N-Back Task in a primary outcome2009: 5 studies, 4 naming the N-Back Task in a primary outcome2010: 11 studies, 4 naming the N-Back Task in a primary outcome20102011: 20 studies, 8 naming the N-Back Task in a primary outcome2012: 14 studies, 6 naming the N-Back Task in a primary outcome2013: 23 studies, 13 naming the N-Back Task in a primary outcome2014: 25 studies, 14 naming the N-Back Task in a primary outcome2015: 25 studies, 13 naming the N-Back Task in a primary outcome20152016: 32 studies, 19 naming the N-Back Task in a primary outcome2017: 51 studies, 24 naming the N-Back Task in a primary outcome2018: 54 studies, 30 naming the N-Back Task in a primary outcome2019: 59 studies, 24 naming the N-Back Task in a primary outcome2020: 30 studies, 14 naming the N-Back Task in a primary outcome20202021: 70 studies, 35 naming the N-Back Task in a primary outcome2022: 62 studies, 34 naming the N-Back Task in a primary outcome2023: 71 studies, 32 naming the N-Back Task in a primary outcome2024: 69 studies, 35 naming the N-Back Task in a primary outcome2025: 67 studies, 29 naming the N-Back Task in a primary outcome20252026: 68 studies, 25 naming the N-Back Task in a primary outcome

2026 is partly planned starts. Not shown: 3 planned to start after 2026.

Show as a table
Matching studies by start year
Start yearStudiesAs a primary outcome
200000
200100
200221
200321
200400
200543
200631
2007107
2008102
200954
2010114
2011208
2012146
20132313
20142514
20152513
20163219
20175124
20185430
20195924
20203014
20217035
20226234
20237132
20246935
20256729
20266825

Library tests named most

  • N-Back Task790 studies, 381 as a primary outcome
  • Stroop Color-Word Test128 studies, 56 as a primary outcome
  • Trail Making Test109 studies, 34 as a primary outcome
  • Digit Span Test94 studies, 32 as a primary outcome
  • Go/No-Go Task87 studies, 32 as a primary outcome
  • Verbal Fluency83 studies, 36 as a primary outcome
  • Verbal Learning82 studies, 40 as a primary outcome
  • Symbol Coding77 studies, 29 as a primary outcome
  • Continuous Performance Test65 studies, 25 as a primary outcome
  • Eriksen Flanker Task55 studies, 32 as a primary outcome

Largest condition groups

Phases

Participants

Lead sponsor: industry 51, NIH 5, other 734. Interventional 724, observational 66.

As a primary outcomeSecondary or other outcomeThe N-Back Task

The studies, newest registration first

Each number opens the study's record on ClinicalTrials.gov.

Registered studies that match the filters, newest registration first, with the library tests each one names and the outcome list that names them.
StudyStartPhaseConditionsParticipantsLead sponsorStatusLibrary tests named, with the latest time point
NCT07903896Start2026PhaseNot applicableConditionsDepression and bipolar disorder, Sleep and sleep disorders, Anxiety, PTSD and OCDParticipants75Lead sponsorOtherStatusRecruitingLibrary tests named
  • N-Back TaskSecondary
  • Eriksen Flanker TaskSecondary
NCT07897214Start2026PhaseNot applicableConditionsOther conditionsParticipants15Lead sponsorOtherStatusRecruitingLibrary tests named
  • N-Back TaskSecondarysame day
NCT07884643Start2026PhaseNot applicableConditionsOther conditionsParticipants70Lead sponsorIndustryStatusRecruitingLibrary tests named
  • Stroop Color-Word TestOther outcome12 weeks
  • Symbol CodingOther outcome12 weeks
  • N-Back TaskOther outcome12 weeks
NCT07873060Start2026PhaseNot applicableConditionsDepression and bipolar disorderParticipants80Lead sponsorOtherStatusRecruitingLibrary tests named
  • N-Back TaskSecondary2 weeks
  • Card Sorting Test (Berg)Secondary2 weeks
  • Balloon RiskSecondary2 weeks
  • Spatial N-Back TaskSecondary2 weeks
NCT07861867Start2027PhasePhase 2ConditionsStroke, Aging, frailty and exerciseParticipants60Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • N-Back TaskPrimary6 months
  • Dimensional Change Card SortSecondary6 months
  • Vocabulary TestSecondary6 months
  • Size Order Memory TestSecondary6 months
  • Pattern and Letter ComparisonSecondary6 months
  • Picture Order Memory TestSecondary6 months
NCT07857239Start2026PhaseNot applicableConditionsOther conditionsParticipants60Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • N-Back TaskSecondarysame day
  • Delay DiscountingSecondarysame day
NCT07848477Start2026PhaseNot applicableConditionsDepression and bipolar disorderParticipants60Lead sponsorOtherStatusRecruitingLibrary tests named
  • Verbal LearningPrimary2 weeks
  • Digit Span TestSecondary2 weeks
  • Symbol CodingSecondary2 weeks
  • N-Back TaskSecondary2 weeks
  • Go/No-Go TaskSecondary2 weeks
  • Paired Associate LearningSecondary2 weeks
  • Probabilistic Reversal LearningSecondary2 weeks
  • Mnemonic Similarity TaskSecondary2 weeks
  • Affective Go/No-GoSecondary2 weeks
  • Grid Pattern Span TaskSecondary2 weeks
NCT07837661Start2026PhaseNot applicableConditionsHealthy volunteersParticipants22Lead sponsorOtherStatusCompletedLibrary tests named
  • N-Back TaskPrimarysame day
NCT07834775Start2026PhaseNot applicableConditionsOther conditionsParticipants70Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Trail Making TestPrimary4 weeks
  • Stroop Color-Word TestSecondary4 weeks
  • N-Back TaskSecondary4 weeks
NCT07833787Start2025PhaseObservationalConditionsOther conditionsParticipants1,500Lead sponsorOtherStatusRecruitingLibrary tests named
  • Digit Span TestSecondary5 years
  • N-Back TaskSecondarysame day
  • Go/No-Go TaskSecondary5 years
  • Attention Network TestSecondarysame day
NCT07831499Start2026PhasePhase 4ConditionsHealthy volunteersParticipants40Lead sponsorOtherStatusRecruitingLibrary tests named
  • N-Back TaskPrimary12 weeks
NCT07830134Start2026PhaseNot applicableConditionsOther conditionsParticipants40Lead sponsorOtherStatusRecruitingLibrary tests named
  • Digit Span TestSecondary3 years
  • N-Back TaskPrimary3 years
  • Letter-Number Sequencing TaskSecondary3 years
NCT07830056Start2025PhasePhase 4ConditionsSleep and sleep disordersParticipants33Lead sponsorOtherStatusRecruitingLibrary tests named
  • N-Back TaskPrimary1 week
  • Go/No-Go TaskPrimary1 week
  • Psychomotor Vigilance TaskPrimary1 week
  • Task Switching TestPrimary1 week
  • Finger Tapping TaskPrimary1 week
  • Balloon RiskSecondary1 week
NCT07809750Start2026PhaseNot applicableConditionsAging, frailty and exerciseParticipants700Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Stroop Color-Word TestPrimarysame day
  • N-Back TaskPrimarysame day
NCT07807631Start2026PhaseNot applicableConditionsOther conditionsParticipants36Lead sponsorOtherStatusCompletedLibrary tests named
  • N-Back TaskPrimary4 weeks
  • Spatial N-Back TaskPrimary4 weeks
NCT07806877Start2026PhaseNot applicableConditionsSchizophrenia and psychosisParticipants60Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Stroop Color-Word TestPrimary6 weeks
  • N-Back TaskSecondary6 weeks
  • Card Sorting Test (Berg)Primary6 weeks
  • Paced Visual Serial Addition TestPrimary6 weeks
  • Oddball Target DetectionSecondary6 weeks
NCT07802990Start2026PhasePhase 1/2ConditionsSubstance use and addictionParticipants28Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • N-Back TaskSecondary3 weeks
  • Tower PlanningSecondary3 weeks
NCT07802860Start2026PhaseNot applicableConditionsPain and fatigueParticipants30Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • N-Back TaskSecondary6 months
NCT07799584Start2026PhaseNot applicableConditionsMild cognitive impairmentParticipants120Lead sponsorOtherStatusRecruitingLibrary tests named
  • Verbal LearningPrimary6 months
  • Digit Span TestPrimary8 weeks
  • N-Back TaskPrimary8 weeks
  • Go/No-Go TaskPrimary8 weeks
  • Mnemonic Similarity TaskPrimary6 months
NCT07793604Start2026PhaseNot applicableConditionsOther conditionsParticipants180Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Trail Making TestPrimary9 weeks
  • Verbal FluencyPrimary9 weeks
  • N-Back TaskSecondary9 weeks
  • Delayed Match-to-SampleSecondary9 weeks
NCT07772947Start2024PhaseNot applicableConditionsStrokeParticipants50Lead sponsorOtherStatusCompletedLibrary tests named
  • N-Back TaskPrimary2 weeks
NCT07772765Start2026PhaseNot applicableConditionsOther conditionsParticipants216Lead sponsorOtherStatusRecruitingLibrary tests named
  • Trail Making TestOther outcome4 months
  • Verbal LearningOther outcome4 months
  • N-Back TaskSecondary4 months
  • Picture Naming TestOther outcome4 months
  • Matrix ReasoningOther outcome4 months
  • Letter-Number Sequencing TaskSecondary4 months
  • Digits-in-Noise TaskPrimary4 months
  • Gap Detection TaskSecondary10 weeks
NCT07759648Start2025PhaseObservationalConditionsHealthy volunteersParticipants47Lead sponsorOtherStatusCompletedLibrary tests named
  • N-Back TaskPrimarysame day
NCT07749144Start2026PhaseNot applicableConditionsAging, frailty and exerciseParticipants120Lead sponsorOtherStatusCompletedLibrary tests named
  • N-Back TaskPrimary8 weeks
  • Eriksen Flanker TaskPrimary8 weeks
  • Task Switching TestPrimary8 weeks
NCT07734623Start2025PhaseNot applicableConditionsSubstance use and addictionParticipants60Lead sponsorOtherStatusRecruitingLibrary tests named
  • N-Back TaskSecondary2 years
  • Betting Choice TaskSecondary2 years

Page 1 of 32

Questions, answered from the data

How many clinical trials use the N-Back Task?

790 registered studies on ClinicalTrials.gov name it in an outcome measure, 381 of them in a primary outcome.

In which conditions do trials use the N-Back Task?

Most often in depression and bipolar disorder (79), aging, frailty and exercise (68) and substance use and addiction (68).

Do new trials use the N-Back Task more or less?

4.8% of the studies that started in 2021 to 2025 name it, against 5.0% of those that started in 2016 to 2020: a share 5% smaller.

Which tests do trials use with the N-Back Task?

The Stroop Color-Word Test (128 studies), the Trail Making Test (109 studies) and the Digit Span Test (94 studies).

How many participants do phase 2 trials that use the N-Back Task enroll?

Half of the phase 2 studies that name it enroll 55 participants or fewer, and the middle half enroll 20 to 97. 56 of them give a size.

When do trials measure the N-Back Task?

Half of the primary outcomes that name the N-Back Task are measured within 4 weeks of the start, and the middle half from the first day to 12 weeks. 350 primary outcomes give a duration.

How many completed trials that use the N-Back Task have reported results?

212 of the 435 completed studies that name it, 49%, have reported results: 93 posted them on ClinicalTrials.gov, 151 have a results paper linked to the registry record, and 32 did both. The other 223 show neither. Of all completed studies with a cognitive outcome, 46% have reported results.

More on tests in clinical trials

  • 1-Back Task: what it measures, its scores, and a version to try
  • 2-Back Task: what it measures, its scores, and a version to try
  • All 101 tests in clinical trials
  • Cognitive tests by condition
  • Every registered study, by test, condition, phase and year

How the studies are counted

For each test family, the census runs ClinicalTrials.gov's own outcome search for the family's names and reads every study first posted by the day the family was counted. These studies were read on 10 November 2026. A study counts once on a page, however many tests it names. Counts for a test cover every version of the task under any of its names, so a page can count studies that used a commercial version.

The census adds two things to each record and changes nothing in it: which outcome list names the test (primary, then secondary, then other), and the condition groups, matched on the study's condition names and MeSH terms. A study can fall in several groups; one whose only condition is cognitive impairment or decline falls in “Cognitive impairment and decline”. Studies that name only instruments outside the library count in every total and share but are not listed.

A second read on 10 November 2026 added each study's overall status, whether results are posted, its intervention types, the countries of its sites and the time frame of the outcome that names each test. A time frame counts by the latest time point it names: “Baseline, 12 and 24 weeks” is 24 weeks, a single visit is within a day, and one that names no duration, such as “end of treatment”, is left out of the timings.

A third read on 10 November 2026 added the papers the registry links to each study: those its sponsor lists as reporting results, and those PubMed links to it through the study's NCT number. A study has a results paper when one of them came out in or after the month of its primary completion and PubMed does not class it as a protocol, review or comment. A paper that never gives the NCT number is not linked, so some studies counted as reporting neither did publish.

Source: ClinicalTrials.gov, a database of the U.S. National Library of Medicine, which does not endorse these pages. Every study line is in the data release 2.1.0, and the explorer's own file is clinical-trials-studies.json.

The census counts 1-Back Task and 2-Back Task as one test family, so this page counts their studies together: 790 studies.

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