Attention
Inspection Time Task
Also called: IT task, visual inspection time, line length discrimination task, pi figure task, perceptual speed task
Measure the speed of visual processing without speeded movement: how long two briefly flashed lines must show before people can tell which is longer.
5-6 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
- 11
- Evidence grade
- C
- Registered clinical studies
- 1
What it measures
A measure of how quickly the eye and brain take in a simple display. Two lines joined at the top, one clearly longer, flash for one of nine fixed durations from about 17 to 200 ms, each shown equally often, and a pattern of lines then covers them. Participants press the arrow key for the side of the longer line, with no time limit. The score is the display duration at which 75 percent of answers are right.
Constructs
- Speed of visual processing
- Inspection time
- Brief display discrimination
Research uses
- Cognitive aging research
- Intelligence and individual differences research
- Visual processing research
How the paradigm works
The Inspection Time Task measures how long a simple figure must be in view for a person to judge it reliably: the speed of early visual processing, measured with no speeded movement (Vickers, Nettelbeck and Willson, 1972). Two vertical lines joined at the top, one twice as long as the other, flash in the middle of the screen, and a pattern of lines then covers them. The briefer the flash, the closer accuracy falls to chance. Inspection time has been linked to intelligence (Grudnik and Kranzler, 2001) and to cognitive aging (Ritchie, Tucker-Drob and Deary, 2014).
More about the paradigm
On each trial a cross shows for 500 ms, then the figure for one of nine fixed durations, about 17, 33, 50, 67, 83, 100, 133, 167 or 200 ms (1 to 12 frames of a 60 Hz screen), then a mask for 500 ms: the crossbar, both lines at full length and 12 more vertical lines at seeded places, so neither line seems to grow into the mask. Participants then press the left or right arrow key for the side of the longer line, with no time limit; keys pressed earlier are not taken. Each duration appears 12 times (standard; 8 to 16), with the long line on each side equally often, for 108 trials in a seeded order after 6 practice trials with feedback, about 5 minutes. Every duration is set before the session, as in the method of constant stimuli the Lothian Birth Cohort studies used (Deary and colleagues, 2007): no answer changes a later display, and there is no training mode. Displays switch on screen frames, the measured durations are saved on every trial, and trials more than one frame off plan leave the score. Desktop and laptop only.
The main score is the display duration at which 75 percent of answers are right, from a monotone fit to the share right at each duration, interpolated on log duration; lower means faster visual processing. Accuracy overall and at each duration are also reported. Scores support research and do not diagnose.
Scores
- Inspection Timems
- The display duration at which 75 percent of answers are right, from a monotone fit to the share right at each duration, interpolated on log duration.
- Lower is better; the figure needed less time in view
- Inspection Time at Longest Durationflag
- 1 when even the longest duration stayed under 75 percent right, so the score is the longest duration and only a lower bound.
- 1 is flagged for review
- Inspection Time at Shortest Durationflag
- 1 when the shortest duration was already at or above 75 percent right, so the score is the shortest duration and an upper bound.
- 1 is noted for review
- Accuracy by Duration%
- Share right at each display duration, keyed by its planned length in whole ms.
- Rises with the duration
- Accuracy%
- Share right over all durations. The Lothian Birth Cohort studies scored the number right.
- Higher is better
- Accuracy at the Longest Durations%
- Share right at the two longest durations, about 167 and 200 ms, where the longer line is plain to see.
- Under 50% is invalid and under 80% is flagged for review
- Longest-Duration Trials Scoredtrials
- Answers at the two longest durations that count toward the score.
- Informational
- Median Answer Timems
- Median time from the question to the answer.
- Informational; the answer has no time limit
- Anticipationscount
- Answers under 100 ms from the question, which are not scored.
- Lower is better
- Early Key Pressescount
- Arrow keys pressed before the question appeared, which are not taken as answers.
- Informational
- Frame Intervalms
- Median time between screen frames during the trials.
- About 16.7 on a 60 Hz screen
- Refresh RateHz
- Screen refresh rate from the frame interval.
- Informational
- Displays on Time%
- Share of answered trials whose figure showed within one frame of plan; only these are scored.
- Under 0.9 is flagged for review
- Completed Trialstrials
- Trials answered in the scored run.
- Fewer than planned is flagged for review
- Planned Trialstrials
- Trials the run set out to show.
- Informational
Use and evidence
11 papers from 2021 to 2025 name this task in their title or abstract, about the same as from 2016 to 2020. That ranks it 366 of 395 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 2 |
| 2024 | 2 |
| 2023 | 2 |
| 2022 | 1 |
| 2021 | 4 |
| 2020 | 3 |
| 2019 | 3 |
| 2018 | 1 |
| 2017 | 2 |
| 2016 | 2 |
| 2015 | 3 |
| 2014 | 1 |
| 2013 | 5 |
| 2012 | 2 |
| 2011 | 4 |
| 2010 | 3 |
| 2009 | 0 |
| 2008 | 5 |
| 2007 | 3 |
| 2006 | 3 |
| 2005 | 2 |
| 2004 | 4 |
| 2003 | 1 |
| 2002 | 2 |
| 2001 | 3 |
| 2000 | 1 |
Use grade E
Fewer than 30 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
- 4
- Papers on reliability or validity
- 16
- Registered clinical studies using it as an outcome
- 1
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.
- Display
- On a dark panel: a cross for 500 ms, then two vertical lines joined at the top, 180 and 90 px long under a 90 px crossbar, then a mask for 500 ms: the crossbar, both lines at full length and 12 more vertical lines at seeded places.
- Durations
- The lines show for about 17, 33, 50, 67, 83, 100, 133, 167 or 200 ms, set as 1 to 12 frames of a 60 Hz screen and shown in whole frames of the screen's own rate.
- Answer
- Press the left or right arrow key for the side of the longer line, with no time limit. Keys pressed before the question are counted and not taken as answers.
- Trials
- 12 at each duration (standard; 8 to 16): 108 trials in a seeded order, with the long line on each side equally often at each duration.
- Practice
- 6 trials, 2 each at 200, 133 and 100 ms, with feedback for 1,000 ms.
- Fixed times
- Every display time is set before the session, and no answer changes it: there is no staircase and no training mode.
- Score
- The display time at which 75 percent of answers are right, from a monotone fit to the share right at each duration, interpolated on log duration. Trials whose lines ran more than one frame off plan, and answers under 100 ms, leave the score.
The figure keeps the proportions of the Lothian Birth Cohort 1936 version, drawn in screen pixels with no calibration. Durations are whole frames of a 60 Hz screen, so the shortest is about 17 ms, where that version started at 6 ms.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: inspection_time_test from the scored run, the left or right arrow after the mask, with no time limit (chance 50%; the long line is on each side in half the trials at every duration), graded from the saved side. Below chance invalidates and not above chance is flagged; one arrow on 90% of answers invalidates when accuracy is not above chance. Answer times run from the question. Responses under 100 ms follow the timed-test rule. Under 50% right at the two longest durations, on at least eight such trials, invalidates and under 80% is flagged. No fitted duration, a fit at the longest duration, a run short of its planned trials, or fewer than 90% of figures within one frame of plan is flagged for review.
Why these rules
Accuracy significantly below chance (one-sided exact test, p < .05) cannot come from guessing; it means the response mapping was reversed or the task was not followed (Slick, Sherman and Iverson 1999 treat below-chance forced-choice performance as definite response bias). Chance-level accuracy can be a real result in impaired participants, so it is only flagged. One option on at least 90% of answered trials, when the correct options are balanced and accuracy is not above chance, means the answers did not depend on the items (the task counterpart of long-string responding in surveys; Curran 2016). An answer under 100 ms from the question was pressed before the question could be read. At the two longest durations the longer line is plain to see, so errors there mean the figure could not be seen or the task was not followed; Deary and Ritchie (2016) kept only people with 16 or more of 20 right at those durations. The display time carries the score, so trials whose figure ran late leave it.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| Trials at each duration | 12 | 8 to 16 |
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 Inspection Time Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Vickers, Nettelbeck and Willson, 1972; Deary and colleagues, 2007), with the standard settings (trials at each duration: 12). The main score was inspection time (the display duration at which 75 percent of answers are right, from a monotone fit to the share right at each duration, interpolated on log duration).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Vickers, D., Nettelbeck, T., & Willson, R. J. (1972). Perceptual indices of performance: The measurement of 'inspection time' and 'noise' in the visual system. Perception, 1(3), 263-295. https://doi.org/10.1068/p010263The task: two lines of clearly unequal length, shown briefly and then masked, with no time pressure on the answer.
- Deary, I. J., Gow, A. J., Taylor, M. D., Corley, J., Brett, C., Wilson, V., Campbell, H., Whalley, L. J., Visscher, P. M., Porteous, D. J., & Starr, J. M. (2007). The Lothian Birth Cohort 1936: A study to examine influences on cognitive ageing from age 11 to age 70 and beyond. BMC Geriatrics, 7, 28. https://doi.org/10.1186/1471-2318-7-28The figure's proportions, a mask of vertical lines for 500 ms, and 15 fixed durations from 6 to 200 ms with 10 trials each.
- Deary, I. J., & Ritchie, S. J. (2016). Processing speed differences between 70- and 83-year-olds matched on childhood IQ. Intelligence, 55, 28-33. https://doi.org/10.1016/j.intell.2016.01.002The method of constant stimuli, answers taken only after the mask, and the check of accuracy at the two longest durations.
- Grudnik, J. L., & Kranzler, J. H. (2001). Meta-analysis of the relationship between intelligence and inspection time. Intelligence, 29(6), 523-535. https://doi.org/10.1016/S0160-2896(01)00078-2
- Ritchie, S. J., Tucker-Drob, E. M., & Deary, I. J. (2014). A strong link between speed of visual discrimination and cognitive ageing. Current Biology, 24(15), R681-R683. https://doi.org/10.1016/j.cub.2014.06.012
- Stough, C., Bates, T. C., Mangan, G. L., & Colrain, I. (2001). Inspection time and intelligence: Further attempts to eliminate the apparent movement strategy. Intelligence, 29(3), 219-230. https://doi.org/10.1016/S0160-2896(00)00053-2Masks that let the short line seem to grow give a cue that weakens the link with intelligence.
Source papers
- Deary IJ, Gow AJ, Taylor MD, Corley J, Brett C, Wilson V, Campbell H, Whalley LJ, Visscher PM, Porteous DJ, Starr JM (2007). The Lothian Birth Cohort 1936: a study to examine influences on cognitive ageing from age 11 to age 70 and beyond. BMC Geriatrics, 7:28.Paradigm source, Adults about 70 years
Questions
How long does the Inspection Time Task take?
About 5 to 6 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?
Inspection Time, Inspection Time at Longest Duration, Inspection Time at Shortest Duration, Accuracy by Duration, Accuracy, Accuracy at the Longest Durations, Longest-Duration Trials Scored, Median Answer Time, Anticipations, Early Key Presses, Frame Interval, Refresh Rate, Displays on Time, Completed Trials and Planned Trials. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Inspection Time Task used in research?
11 papers from 2021 to 2025 name it in their title or abstract, about the same as from 2016 to 2020. That ranks it 366 of 395 test families in the ConductCognition test census (use grade E). Source: ConductCognition test census 0.14.0, counted 31 October 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Inspection Time Task have?
In the published research, 4 papers report its test-retest reliability and 1 registered clinical study uses it as an outcome (evidence grade C in the ConductCognition test census).
Which settings can a researcher change?
Trials at each duration (8 to 16). 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.
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