Attention
Clock Vigilance Test
Also called: Mackworth clock test, Mackworth clock, clock test, vigilance clock task
Measure vigilance over a long watch: a pointer steps around a plain clock face once a second, and participants press when it jumps two steps at once, scored by detections per quarter and false alarms.
12-13 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
- 30
- Evidence grade
- C
- Registered clinical studies
- 4
What it measures
Measures vigilance, the ability to keep spotting rare events over a long, dull watch. A pointer steps around a plain clock face once a second, and participants press the space bar whenever it jumps two steps at once. Detections are scored by quarter of the session to show the vigilance decrement.
Constructs
- Vigilance
- Sustained attention
- Signal detection
Research uses
- Vigilance and time-on-task research
- Fatigue, sleep loss and alertness studies
- Within-study group comparison
How the paradigm works
The Clock Vigilance Test measures vigilance: how well a person keeps detecting rare events through a long, dull watch. A pointer moves around a plain clock face, one step every second, 100 steps to a turn. Now and then it moves two steps at once, a double jump, and the participant presses the space bar on seeing one. A press within 8 seconds of a double jump detects it.
More about the paradigm
The test follows Mackworth's (1948) clock test, built to study radar watchkeepers: one-second steps on a face with no marks, the double jump as the signal, 8 seconds to report it and scoring by period. Mackworth's sessions ran up to two hours with 12 double jumps in each half hour, and detections fell after the first half hour. This version is shorter, 10 minutes as standard (5 to 30 in the settings), so its double jumps come more often, about one step in 25: 24 in the standard session, six in each quarter, at places drawn from the session's seed at least 10 seconds apart. Each step is drawn on the screen frame nearest its time, counted from the clock's start, so the pace never drifts. A one-minute practice with a message after each press comes first; the watch itself gives no messages.
The main score is the share of double jumps detected. The test also reports detections in each quarter of the session and the vigilance decrement, the first quarter minus the last; false alarms, presses with no double jump in the 8 seconds before them, in total, per minute and by quarter; and the median detection time and its change from the first quarter to the last. Presses under 100 ms after a double jump are counted as anticipations. Over a watch, false alarms often fall along with detections, so the two are best read together (Klein and Feltmate, 2025). Scores support research and do not diagnose.
Scores
- Hit Rate%
- Share of the double jumps shown that were detected by a press within 8 seconds.
- Higher is better
- Hit Rate, First Quarter%
- Share of double jumps detected in the first quarter of the session.
- Higher is better
- Hit Rate, Second Quarter%
- Share of double jumps detected in the second quarter of the session.
- Higher is better
- Hit Rate, Third Quarter%
- Share of double jumps detected in the third quarter of the session.
- Higher is better
- Hit Rate, Last Quarter%
- Share of double jumps detected in the last quarter of the session.
- Higher is better
- Vigilance Decrement%
- Hit rate in the first quarter minus hit rate in the last quarter.
- Positive values mean more double jumps were missed late in the watch
- False Alarmscount
- Presses with no double jump in the 8 seconds before them.
- Lower is better
- False Alarms per Minutescore
- False alarms per minute of clock drawn.
- Lower is better
- False Alarms, First Quartercount
- False alarms in the first quarter of the session.
- Informational
- False Alarms, Second Quartercount
- False alarms in the second quarter of the session.
- Informational
- False Alarms, Third Quartercount
- False alarms in the third quarter of the session.
- Informational
- False Alarms, Last Quartercount
- False alarms in the last quarter of the session.
- Informational
- Median Detection Timems
- Median time from a double jump to the press that detected it.
- Lower is faster
- Change in Detection Timems
- Median detection time in the last quarter minus in the first quarter.
- Positive values mean slower detection late in the watch
- Anticipationscount
- Double jumps with a press under 100 ms after them, which detects nothing.
- Quality check
- Double Jumpscount
- Double jumps drawn as planned.
- Informational
- Double Jumps Not Showncount
- Double jumps left out because the page stopped drawing when they came due.
- Quality check
- Steps Showncount
- Steps of the pointer drawn, one a second.
- Under 90% of the planned steps is invalid
- Planned Stepscount
- Steps the session planned.
- Informational
Use and evidence
30 papers from 2021 to 2025 name this task in their title or abstract, up 100% compared with 2016 to 2020. That ranks it 301 of 395 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 5 |
| 2024 | 6 |
| 2023 | 7 |
| 2022 | 6 |
| 2021 | 6 |
| 2020 | 4 |
| 2019 | 2 |
| 2018 | 1 |
| 2017 | 5 |
| 2016 | 3 |
| 2015 | 1 |
| 2014 | 2 |
| 2013 | 0 |
| 2012 | 0 |
| 2011 | 1 |
| 2010 | 1 |
| 2009 | 4 |
| 2008 | 1 |
| 2007 | 3 |
| 2006 | 2 |
| 2005 | 4 |
| 2004 | 1 |
| 2003 | 0 |
| 2002 | 2 |
| 2001 | 1 |
| 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
- 0
- Papers on reliability or validity
- 7
- 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.
- Clock
- A pointer on a plain white face with no marks, drawn by code: 100 steps to a turn, one step every second, each step drawn on the screen frame nearest its time from the clock's start.
- Double jumps
- The pointer moves 2 steps at once. About one step in 25: 6 in each quarter of the standard session, 24 in all, at seeded places at least 10 seconds apart, none in the first 10 seconds or the last 8.
- Answer
- The space bar. A press within 8 seconds of a double jump detects it; a press with no double jump in the 8 seconds before it is a false alarm.
- Length
- 10 minutes (standard; 5 to 30) without a break, saved one row per minute.
- Practice
- 1 minute with 4 double jumps and a message after each press and each missed double jump.
- Scoring
- Hit rate overall and in each quarter of the session; the vigilance decrement is the first quarter minus the last. Presses under 100 ms after a double jump count as anticipations.
Mackworth (1948) ran sessions of up to two hours with 12 double jumps in each half hour. This version is shorter and its double jumps come more often, so its decrement may differ in size from his.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: clock_vigilance_minute from the scored run, one per minute, read as one trial per step drawn: a press is needed within 8 s of each double jump and on no other step. Presses mostly away from double jumps invalidate, and presses that do not separate them are flagged. Missed double jumps are the measure, so only a session with no presses is invalid, and a run of misses covering half the double jumps is flagged and withholds the percentile. The clock drawn for under 90% of the planned time, or more false alarms than double jumps, invalidates; more than half as many false alarms as double jumps, or over 10% of double jumps not drawn as planned, is flagged and withholds the percentile. A press under 100 ms after a double jump answers nothing. Responses under 100 ms follow the timed-test rule.
Why these rules
Responses concentrated on trials that needed none (one-sided Fisher exact test, p < .05) mean the instructions were reversed and invalidate; responses that do not separate the two trial types are flagged. Missed targets are what this test measures, so missed responses never invalidate on their own. A session with no responses is invalid. An unbroken run of misses covering at least half the response trials (minimum 8) may mean the participant stopped, so the session is flagged and its percentile withheld. With an 8 second window, pressing often would catch every double jump, so false alarms set the limit: more presses with no double jump than double jumps means the presses did not follow the clock. A vigilance session must be watched through, and a hidden page stops the clock being drawn. The limits are ConductScience choices; Mackworth (1948) ran supervised sessions. A hidden tab lets the study, delay or response timers run without the participant, so a percentile is withheld after one.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Session length (minutes) | 10 | 5 to 30 |
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 Clock Vigilance Test in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Mackworth, 1948), with the standard settings (session length (minutes): 10). The main score was hit rate (share of the double jumps shown that were detected by a press within 8 seconds).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Mackworth, N. H. (1948). The breakdown of vigilance during prolonged visual search. Quarterly Journal of Experimental Psychology, 1(1), 6-21. https://doi.org/10.1080/17470214808416738
- Lichstein, K. L., Riedel, B. W., & Richman, S. L. (2000). The Mackworth Clock Test: A computerized version. The Journal of Psychology, 134(2), 153-161. https://doi.org/10.1080/00223980009600858A computerized version of the clock checked against the original.
- Klein, R. M., & Feltmate, B. B. T. (2025). The vigilance decrement: Its first 75 years. Frontiers in Cognition, 4, 1632885. https://doi.org/10.3389/fcogn.2025.1632885Reading detections and false alarms together over a watch.
Source papers
- Mackworth NH (1948). The breakdown of vigilance during prolonged visual search. Quarterly Journal of Experimental Psychology, 1(1):6-21.Paradigm source, Adults
Questions
How long does the Clock Vigilance Test take?
About 12 to 13 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?
Hit Rate, Hit Rate, First Quarter, Hit Rate, Second Quarter, Hit Rate, Third Quarter, Hit Rate, Last Quarter, Vigilance Decrement, False Alarms, False Alarms per Minute, False Alarms, First Quarter, False Alarms, Second Quarter, False Alarms, Third Quarter, False Alarms, Last Quarter, Median Detection Time, Change in Detection Time, Anticipations, Double Jumps, Double Jumps Not Shown, Steps Shown and Planned Steps. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Clock Vigilance Test used in research?
30 papers from 2021 to 2025 name it in their title or abstract, up 100% compared with 2016 to 2020. That ranks it 301 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 Clock Vigilance Test have?
In the published research, 0 papers report its test-retest reliability and 4 registered clinical studies use it as an outcome (evidence grade C in the ConductCognition test census).
Which settings can a researcher change?
Session length (minutes) (5 to 30). 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.
Every test: the full test list.
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