Clinical trials data
Cognitive tests in healthy volunteer trials: 656 registered studies
Every registered healthy volunteers study on ClinicalTrials.gov that names a cognitive test in an outcome measure: the tests used most, how often as a primary outcome, which tests go together, how large the studies are and when they measure the outcome.
- Registered healthy volunteers studies name a cognitive test in an outcome
- 656
- Led by industry
- 98
The tests healthy volunteer trials use most
The Stroop Color-Word Test leads: 98 of the 656 studies name it, 15%. Next comes the Trail Making Test (68). As a primary outcome, the Stroop Color-Word Test leads with 48 studies.
- 1
Stroop Color-Word Test98 studies, 48 as a primary outcome
- 2
Trail Making Test68 studies, 31 as a primary outcome
- 3
Digit Span Test64 studies, 31 as a primary outcome
- 4
Verbal Learning56 studies, 26 as a primary outcome
- 5
Symbol Coding56 studies, 18 as a primary outcome
- 6
N-Back Task51 studies, 26 as a primary outcome
- 7
Go/No-Go Task42 studies, 22 as a primary outcome
- 8
Verbal Fluency39 studies, 13 as a primary outcome
- 9
Psychomotor Vigilance Task31 studies, 11 as a primary outcome
- 10
Eriksen Flanker Task30 studies, 18 as a primary outcome
- 11
Paired Associate Learning30 studies, 12 as a primary outcome
- 12
Emoji Emotion Recognition22 studies, 7 as a primary outcome
- 13
Choice Reaction Time20 studies, 8 as a primary outcome
- 14
Simple Reaction Time20 studies, 8 as a primary outcome
- 15
Card Sorting Test (Berg)18 studies, 8 as a primary outcome
- 16
Continuous Performance Test18 studies, 7 as a primary outcome
- 17
Rapid Visual Information Processing18 studies, 4 as a primary outcome
- 18
Task Switching Test16 studies, 12 as a primary outcome
- 19
Corsi Block-Tapping Test16 studies, 7 as a primary outcome
- 20
Matrix Reasoning16 studies, 7 as a primary outcome
- 21
Probabilistic Reversal Learning14 studies, 10 as a primary outcome
- 22
Hidden Path Learning13 studies, 6 as a primary outcome
- 23
Antisaccade Task12 studies, 12 as a primary outcome
- 24
Letter-Number Sequencing Task12 studies, 5 as a primary outcome
- 25
Dimensional Change Card Sort12 studies, 4 as a primary outcome
A test as a primary outcomeOnly in secondary or other outcomes
10% of healthy volunteers studies name only instruments outside the library, such as clinician-administered screening scales. They count in every figure on this page and are not listed. The explorer below holds all 160 tests.
Tests used together
- Stroop Color-Word Test and Trail Making Test31 studies name both
- Digit Span Test and Stroop Color-Word Test20 studies name both
- Digit Span Test and Trail Making Test19 studies name both
- Trail Making Test and Verbal Learning13 studies name both
- Card Sorting Test (Berg) and Stroop Color-Word Test12 studies name both
- Digit Span Test and Verbal Fluency11 studies name both
- Trail Making Test and Verbal Fluency11 studies name both
- Card Sorting Test (Berg) and Digit Span Test10 studies name both
- Digit Span Test and Verbal Learning10 studies name both
- Choice Reaction Time and Simple Reaction Time9 studies name both
Studies by start year
A test as a primary outcomeOnly in secondary or other outcomes
Show as a table
| Start year | Studies | A test as a primary outcome |
|---|---|---|
| 2000 | 0 | 0 |
| 2001 | 1 | 1 |
| 2002 | 1 | 0 |
| 2003 | 1 | 1 |
| 2004 | 2 | 0 |
| 2005 | 1 | 1 |
| 2006 | 3 | 3 |
| 2007 | 4 | 2 |
| 2008 | 3 | 1 |
| 2009 | 1 | 1 |
| 2010 | 11 | 9 |
| 2011 | 20 | 10 |
| 2012 | 10 | 7 |
| 2013 | 19 | 11 |
| 2014 | 20 | 15 |
| 2015 | 27 | 14 |
| 2016 | 23 | 11 |
| 2017 | 34 | 17 |
| 2018 | 31 | 14 |
| 2019 | 40 | 24 |
| 2020 | 42 | 24 |
| 2021 | 52 | 21 |
| 2022 | 54 | 30 |
| 2023 | 43 | 27 |
| 2024 | 62 | 30 |
| 2025 | 77 | 37 |
| 2026 | 69 | 39 |
Phases and sponsors
By phase
- Early phase 118 studies, 8 as a primary outcome
- Phase 175 studies, 29 as a primary outcome
- Phase 1/28 studies, 4 as a primary outcome
- Phase 214 studies, 6 as a primary outcome
- Phase 2/31 studies, 1 as a primary outcome
- Phase 38 studies, 5 as a primary outcome
- Phase 420 studies, 10 as a primary outcome
- Not applicable437 studies, 250 as a primary outcome
- Observational74 studies, 41 as a primary outcome
- Not given1 studies, 0 as a primary outcome
Sponsors and study types
Lead sponsor: industry 98, NIH 9, universities, hospitals and others 549. Interventional 582, observational 74.
Status, results, interventions and countries
Status
- Recruiting108 studies, 53 as a primary outcome
- Not yet recruiting30 studies, 17 as a primary outcome
- Active, not recruiting22 studies, 9 as a primary outcome
- Completed384 studies, 214 as a primary outcome
- Stopped early34 studies, 19 as a primary outcome
- Status unknown78 studies, 42 as a primary outcome
What they test
- Behavioral140 studies, 88 as a primary outcome
- Drug170 studies, 78 as a primary outcome
- Device101 studies, 55 as a primary outcome
- Dietary supplement77 studies, 46 as a primary outcome
- Procedure11 studies, 3 as a primary outcome
- Diagnostic test15 studies, 7 as a primary outcome
- Biological2 studies, 2 as a primary outcome
- Combination product3 studies, 2 as a primary outcome
- Genetic6 studies, 2 as a primary outcome
- Other177 studies, 93 as a primary outcome
- None given33 studies, 18 as a primary outcome
Intervention types as registered. A study can list several; observational studies often list none.
Where their sites are
- United States191 studies, 114 as a primary outcome
- France46 studies, 23 as a primary outcome
- United Kingdom42 studies, 13 as a primary outcome
- Türkiye37 studies, 23 as a primary outcome
- China36 studies, 27 as a primary outcome
- Switzerland31 studies, 11 as a primary outcome
- Germany26 studies, 8 as a primary outcome
- Spain26 studies, 13 as a primary outcome
- Belgium24 studies, 13 as a primary outcome
- Canada22 studies, 14 as a primary outcome
- Italy16 studies, 10 as a primary outcome
- Taiwan16 studies, 10 as a primary outcome
48 countries in all. A study with sites in several counts in each; 36 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 healthy volunteers studies: 122 of 384, 32%
Every completed study with a cognitive outcome: 3,626 of 7,953, 46%
| Results | Completed healthy volunteers studies | Every completed study |
|---|---|---|
| Results on ClinicalTrials.gov and a paper | 11, 3% | 776, 10% |
| Results on ClinicalTrials.gov only | 38, 10% | 1,139, 14% |
| A results paper only | 73, 19% | 1,711, 22% |
| Neither | 262, 68% | 4,327, 54% |
How many participants they enroll
- Early phase 161 median, 24 to 141
- Phase 130 median, 20 to 45
- Phase 264 median, 41 to 91
- Phase 444 median, 30 to 70
- Not applicable60 median, 35 to 104
- Observational121 median, 60 to 355
Show as a table
| Phase | Studies with a size | Median | Middle half |
|---|---|---|---|
| Early phase 1 | 17 | 61 | 24 to 141 |
| Phase 1 | 73 | 30 | 20 to 45 |
| Phase 2 | 13 | 64 | 41 to 91 |
| Phase 4 | 20 | 44 | 30 to 70 |
| Not applicable | 432 | 60 | 35 to 104 |
| Observational | 72 | 121 | 60 to 355 |
When the cognitive outcome is measured
Latest time point of each outcome
- Within a day364 outcomes, 204 as a primary outcome
- Up to 4 weeks284 outcomes, 126 as a primary outcome
- 1 to 3 months263 outcomes, 114 as a primary outcome
- 3 to 6 months84 outcomes, 45 as a primary outcome
- 6 to 12 months64 outcomes, 33 as a primary outcome
- 1 to 2 years28 outcomes, 11 as a primary outcome
- Over 2 years32 outcomes, 20 as a primary outcome
- No duration given107 outcomes, 53 as a primary outcome
A test as a primary outcomeOnly in secondary or other outcomes
1,119 of the 1,226 outcome measures give a duration. A single visit counts as within a day.
Median time to the primary outcome, by test
| Test | Primary outcomes | Median |
|---|---|---|
| Stroop Color-Word Test | 42 | 4 weeks |
| Trail Making Test | 29 | 5 weeks |
| Digit Span Test | 28 | 6 weeks |
| N-Back Task | 24 | 1 day |
| Verbal Learning | 23 | 3 weeks |
| Go/No-Go Task | 21 | same day |
| Symbol Coding | 18 | 5 weeks |
| Eriksen Flanker Task | 16 | 5 weeks |
| Antisaccade Task | 12 | same day |
| Paired Associate Learning | 12 | 6 days |
Explore the healthy volunteers studies
590 studies match. 319 name a library test in a primary outcome. Median size 60 participants. Median time to the primary outcome: 2 weeks.
Loading 590 studies; the filters turn on when they arrive.
2026 is partly planned starts. Not shown: 2 that started before 2000 and 3 planned to start after 2026.
Show as a table
| Start year | Studies | As a primary outcome |
|---|---|---|
| 2000 | 0 | 0 |
| 2001 | 1 | 1 |
| 2002 | 1 | 0 |
| 2003 | 1 | 1 |
| 2004 | 1 | 0 |
| 2005 | 0 | 0 |
| 2006 | 3 | 3 |
| 2007 | 3 | 2 |
| 2008 | 3 | 1 |
| 2009 | 1 | 1 |
| 2010 | 11 | 9 |
| 2011 | 20 | 9 |
| 2012 | 9 | 6 |
| 2013 | 19 | 11 |
| 2014 | 19 | 15 |
| 2015 | 24 | 11 |
| 2016 | 21 | 10 |
| 2017 | 32 | 16 |
| 2018 | 31 | 14 |
| 2019 | 37 | 22 |
| 2020 | 37 | 21 |
| 2021 | 40 | 19 |
| 2022 | 51 | 28 |
| 2023 | 38 | 25 |
| 2024 | 57 | 26 |
| 2025 | 67 | 28 |
| 2026 | 58 | 36 |
Library tests named most
Largest condition groups
Phases
Participants
Lead sponsor: industry 89, NIH 9, other 492. Interventional 535, observational 55.
As a primary outcomeSecondary or other outcome
The studies, newest registration first
Each number opens the study's record on ClinicalTrials.gov.
| Study | Start | Phase | Conditions | Participants | Lead sponsor | Status | Library tests named, with the latest time point |
|---|---|---|---|---|---|---|---|
| NCT07900893 | Start2026 | PhaseNot applicable | ConditionsSchizophrenia and psychosis, Healthy volunteers | Participants10,000 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07897175 | Start2026 | PhaseNot applicable | ConditionsHealthy volunteers | Participants54 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07879703 | Start2018 | PhaseNot applicable | ConditionsHealthy volunteers | Participants120 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07876193 | Start2025 | PhaseNot applicable | ConditionsHealthy volunteers, Aging, frailty and exercise | Participants15 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07875790 | Start2028 | PhaseNot applicable | ConditionsSchizophrenia and psychosis, Healthy volunteers | Participants325 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07856381 | Start2026 | PhaseObservational | ConditionsSchizophrenia and psychosis, Healthy volunteers | Participants180 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07853807 | Start2026 | PhaseNot applicable | ConditionsSchizophrenia and psychosis, Healthy volunteers | Participants325 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07841457 | Start2027 | PhaseNot applicable | ConditionsHealthy volunteers | Participants20 | Lead sponsorIndustry | StatusNot yet recruiting | Library tests named
|
| NCT07837661 | Start2026 | PhaseNot applicable | ConditionsHealthy volunteers | Participants22 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07831499 | Start2026 | PhasePhase 4 | ConditionsHealthy volunteers | Participants40 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07827651 | Start2025 | PhaseNot applicable | ConditionsHealthy volunteers, Aging, frailty and exercise, Sleep and sleep disorders | Participants64 | Lead sponsorIndustry | StatusActive, not recruiting | Library tests named
|
| NCT07810595 | Start2025 | PhaseNot applicable | ConditionsHealthy volunteers, Aging, frailty and exercise, Anxiety, PTSD and OCD | Participants48 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07809412 | Start2025 | PhaseNot applicable | ConditionsHealthy volunteers | Participants20 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07798349 | Start2026 | PhaseNot applicable | ConditionsHealthy volunteers | Participants120 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07794228 | Start2026 | PhaseNot applicable | ConditionsHealthy volunteers, Anxiety, PTSD and OCD | Participants30 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07792876 | Start2025 | PhaseNot applicable | ConditionsHealthy volunteers, Aging, frailty and exercise | Participants12 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07783074 | Start2026 | PhaseObservational | ConditionsMultiple sclerosis, Healthy volunteers, COVID-19 and long COVID, Pain and fatigue | Participants122 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07759648 | Start2025 | PhaseObservational | ConditionsHealthy volunteers | Participants47 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07755332 | Start2026 | PhaseObservational | ConditionsHealthy volunteers | Participants45 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07752342 | Start2026 | PhaseNot applicable | ConditionsHealthy volunteers, Anxiety, PTSD and OCD | Participants150 | Lead sponsorIndustry | StatusNot yet recruiting | Library tests named
|
| NCT07751614 | Start2026 | PhaseNot applicable | ConditionsHealthy volunteers | Participants60 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07750925 | Start2026 | PhaseNot applicable | ConditionsDepression and bipolar disorder, Healthy volunteers, Anxiety, PTSD and OCD | Participants45 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07732166 | Start2026 | PhaseEarly phase 1 | ConditionsHealthy volunteers | Participants100 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07727577 | Start2026 | PhaseNot applicable | ConditionsHealthy volunteers, Aging, frailty and exercise | Participants50 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07710027 | Start2021 | PhasePhase 1 | ConditionsHealthy volunteers, Anxiety, PTSD and OCD | Participants56 | Lead sponsorIndustry | StatusCompleted | Library tests named
|
Questions, answered from the data
Which cognitive test do healthy volunteer trials use most?
The Stroop Color-Word Test: 98 of the 656 registered studies name it in an outcome measure, 15%. Next come the Trail Making Test (68) and the Digit Span Test (64).
Which cognitive test do healthy volunteer trials use most as a primary outcome?
The Stroop Color-Word Test, named in a primary outcome by 48 studies. 354 of the 656 studies, 54%, name a cognitive test in a primary outcome.
How many participants does a phase 2 healthy volunteer trial enroll?
Half of the phase 2 healthy volunteers studies enroll 64 participants or fewer, and the middle half enroll 41 to 91. 13 of them give a size.
How long after the start do healthy volunteer trials measure a cognitive outcome?
Half of the primary outcomes that name a library test are measured within 2 weeks of the start, and the middle half from the first day to 12 weeks. 553 primary outcomes give a duration.
Which cognitive tests do healthy volunteer trials use together?
The Stroop Color-Word Test with the Trail Making Test most often: 31 studies name both. Next, the Digit Span Test with the Stroop Color-Word Test (20).
How many completed healthy volunteer trials have reported results?
122 of the 384 completed healthy volunteers studies, 32%, have reported results: 49 posted them on ClinicalTrials.gov, 84 have a results paper linked to the registry record, and 11 did both. The other 262 show neither. Of all completed studies with a cognitive outcome, 46% have reported results.
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.
Plan the cognitive outcomes of a healthy volunteers trial
Choose tests with a record in registered trials, and run them in a browser at every site, on the same version each visit.