Attention
Precedence Effect Task
Also called: law of the first wavefront, Haas effect, echo threshold task, lead-lag click task, echo suppression task, click fusion task
Measure how a first sound dominates a quick echo: click pairs through headphones, 1 to 32 ms apart, heard as one click or two.
6-9 minUntimed
Free to start: 10 free participants per account, then $0.99 per participant for academic research, or any yearly plan. Try it here first, with no account.
- Papers, 2021 to 2025
- 58
- Evidence grade
- D
- Registered clinical studies
- 1
What it measures
Measures how a first sound dominates a quick echo of it. Through headphones, participants hear a click on one side followed 1 to 32 ms later by a click on the other side, or a single click, and say whether they heard one click, on the left or right, or two. The main score is the echo threshold, the delay at which half the pairs are heard as two clicks; the lead's dominance comes with it. A research measure, not a hearing test.
Constructs
- Precedence effect
- Echo suppression
- Binaural fusion
- Sound localization
Research uses
- Spatial and binaural hearing research
- Auditory perception research
- Within-study group comparison
How the paradigm works
The precedence effect is the dominance of a first sound over its quick echoes: when a sound and a copy of it from another place arrive a few milliseconds apart, listeners hear one sound, at the first one's place (Wallach, Newman and Rosenzweig, 1949; Litovsky, Colburn, Yost and Guzman, 1999). This task measures it over headphones, as headphone studies do, with clicks placed to the left or the right by a small difference in when they reach the two ears (Brown and Stecker, 2013). It needs headphones and normal hearing. The test starts with the sound setup: the participant turns the device's volume until a steady tone is comfortable, and a six-trial headphone check (Woods, Siegel, Traer and McDermott, 2017) confirms that headphones are in use. By default a failed check ends the test, and the check's result is saved either way.
More about the paradigm
On each trial the participant presses Play and hears a lead click on one side and, 1, 2, 3, 4, 6, 8, 12, 16, 24 or 32 ms after it, a lag click on the other side, or a single click on one side. Each click is a 0.1 ms pulse that reaches both ears, 0.5 ms sooner in the ear on its side, and lead and lag have the same level. The participant answers One click on the left, Two clicks or One click on the right, with no time limit. Each run holds every delay with the lead on each side once and one single click on each side, 22 trials in an order drawn from the session's seed: 110 trials at the standard 5 runs (3 to 8 as a setting). Six practice trials, single clicks and pairs 32 ms apart, give feedback; the test gives none. The delays are set before the session and no answer changes the ones that follow, so there is no staircase. The browser writes the clicks into one sound, each on the sample nearest its time, and starts that sound on the audio clock's sample grid; the output delay the device reports is saved.
The main score is the echo threshold: the delay at which half the pairs are heard as two clicks, from a cumulative Gaussian of the logarithm of the delay fitted by maximum likelihood to the share heard as two at each delay. The lead's dominance is the share of pairs heard as one click that were placed on the lead's side. Echo thresholds for clicks are a few milliseconds, lower over headphones than from loudspeakers (Bianchi, Verhulst and Dau, 2013), and a train of earlier clicks raises them (Freyman, Clifton and Litovsky, 1991), so each pair comes alone, the lead's side changes in a seeded order, and sessions should be compared when run the same way. The single clicks check that the earphones are on the right ears: named on the wrong side, they flag the session.
Scores
- Echo Thresholdms
- The delay at which the fitted curve gives half the pairs heard as two clicks.
- Higher means a later echo was still heard as part of one sound; not a hearing level
- Two Clicks by Delay%
- Share of pairs heard as two clicks at each delay, keyed by the delay in ms.
- Rises with the delay
- Lead Dominance%
- Of the pairs heard as one click, the share placed on the lead click's side.
- 1 means the first click always set the place; 0.5 means neither click did
- Fused Share%
- Share of pairs heard as one click, over all delays.
- Higher means more pairs were heard as one sound
- Single Click Side%
- Share of single clicks named on their own side.
- Near 1 means the earphones were on the right ears; a quarter or less is flagged
- Single Clicks Heard as Two%
- Share of single clicks answered as two clicks.
- Near 0 is expected; half or more makes the session invalid
- Median Answer Timems
- Median time from when the answers opened, after the sound, to the answer.
- Informational; the answer has no time limit
- Anticipationscount
- Answers within 100 ms of the answers opening, which leave the score.
- Half or more of the answers makes the session invalid
- Completed Trialstrials
- Trials answered in the scored run.
- Fewer than planned is flagged for review
- Planned Trialstrials
- Trials the run set out to play.
- Informational
- Headphone Check Passed0/1
- 1 when the headphone check passed (at least 5 of 6 right), 0 when it did not.
- 0 stops the test unless the study set it to continue
- Headphone Check Correctcount
- Headphone check trials answered right, of 6.
- 5 or 6 passes
- Reported Output Delayms
- Output delay the device reported to the browser; empty when the browser does not report it.
- Informational
Use and evidence
58 papers from 2021 to 2025 name this task in their title or abstract, down 33% compared with 2016 to 2020. That ranks it 287 of 495 test families in our census. See the counts for every test.
Show the numbers
| Year | Papers |
|---|---|
| 2025 | 16 |
| 2024 | 16 |
| 2023 | 7 |
| 2022 | 10 |
| 2021 | 9 |
| 2020 | 14 |
| 2019 | 16 |
| 2018 | 20 |
| 2017 | 15 |
| 2016 | 21 |
| 2015 | 21 |
| 2014 | 23 |
| 2013 | 33 |
| 2012 | 27 |
| 2011 | 26 |
| 2010 | 26 |
| 2009 | 17 |
| 2008 | 16 |
| 2007 | 21 |
| 2006 | 18 |
| 2005 | 10 |
| 2004 | 22 |
| 2003 | 19 |
| 2002 | 15 |
| 2001 | 12 |
| 2000 | 10 |
Use grade D
30 to 99 papers from 2021 to 2025.
Evidence grade D
Little published measurement evidence found.
- Papers on test-retest reliability
- 0
- Papers on reliability or validity
- 9
- 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 0.22.0, counted 3 November 2026 from OpenAlex and ClinicalTrials.gov.
Task design
The trial sequence as the test runs in ConductCognition.
- Sound setup
- The participant turns the device's volume until a steady 1 kHz tone is comfortable, then takes a 6-trial headphone check (Woods and colleagues, 2017). By default a failed check ends the test; its result is saved either way.
- Clicks
- Each click is a 0.1 ms pulse as high as the volume-setting tone's peak. It reaches both ears, 0.5 ms sooner in the ear on its side, so it is heard on that side.
- Trial
- Press Play to hear a lead click on one side and, after a delay, a lag click on the other side, or a single click. Choose One click on the left, Two clicks or One click on the right, with no time limit.
- Delays
- Ten delays from the lead's onset to the lag's: 1, 2, 3, 4, 6, 8, 12, 16, 24 and 32 ms. Lead and lag have the same level.
- Trials
- Each run holds every delay with the lead on each side once and one single click on each side, 22 trials in an order drawn from the session's seed. 5 runs (standard, 3 to 8): 110 trials, with no feedback.
- Practice
- 6 trials, single clicks and pairs 32 ms apart, with feedback for 1,000 ms. No pair at a shorter delay is practised.
- Fixed delays
- Every delay is set before the session, and no answer changes the next one: there is no staircase. The browser writes each click on the sample nearest its time and starts the sound on the audio clock's sample grid; the output delay the device reports is saved.
- Score
- The echo threshold: the delay at which half the pairs are heard as two clicks, from a cumulative Gaussian of the logarithm of the delay fitted by maximum likelihood. The lead's dominance: of the pairs heard as one click, the share placed on the lead's side. Answers under 100 ms leave the score.
The clicks play through the participant's own headphones at a volume they chose, and a train of earlier sounds can raise an echo threshold, so compare results within studies run the same way. Single clicks named on the wrong side flag a session, as if the earphones were worn the other way round. The test needs normal hearing and headphones, wired if possible: wireless headphones can add delay and change the sound. It is a research measure, not a hearing test: it gives no hearing level and no pass or fail, and its scores are not a sign of hearing loss. No percentile is given.
Quality checks
Each session is marked valid, needs review or invalid, with the reason, before you see its scores.
Scored rows: precedence_effect_test from the scored run, a button for one click on the left, two clicks or one click on the right after the sound has played, with no time limit. A pair has no correct answer, so only the single clicks are judged: each has one right button of three, its own side. Single clicks below chance or not above chance are flagged; one button on 90% of answers invalidates when the single clicks are not above chance; answers under 100 ms invalidate when they are at least half. Single clicks answered as two clicks on half the trials or more invalidate, and on a quarter or more are flagged. Single clicks named on their own side at most a quarter of the time, no echo threshold within the delays played, a failed headphone check with the test run anyway, or a run short of its planned trials is flagged for review; a headphone check that stopped the test invalidates.
Why these rules
What a listener hears in a pair has no correct answer, so accuracy is judged only on the single clicks, which nearly everyone hears as one click on its side. A single click answered as two means the answers did not follow the sound, and single clicks named on the other side mean the earphones were most likely swapped, which reverses the lead's dominance but not the echo threshold, so it is flagged rather than invalid. 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). The answers open once the sound has played and have no time limit, so an answer under 100 ms was pressed before they opened, and only a session made mostly of such answers is invalid. A threshold outside the delays played cannot be estimated from them. Woods, Siegel, Traer and McDermott (2017) let only listeners who passed the headphone check go on, because a listener on loudspeakers hears the sounds differently; a session that ran after a failed check keeps its scores but not its percentile.
No percentile. Scores and quality flags only.
Running this test
Settings you can change
| Setting | Standard | Allowed |
|---|---|---|
| When the headphone check fails | Stop the test | Stop the test, Continue the test |
| Runs | 5 | 3 to 8 |
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. Needs headphones. Participant devices
- Languages: English, Spanish, French, German, Italian, Portuguese (Brazil), Chinese (Simplified) and Japanese.
- 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 Precedence Effect Task in a web browser (ConductCognition task version 1.0.0, scoring version 1.0.0; Wallach, Newman and Rosenzweig, 1949; Litovsky, Colburn, Yost and Guzman, 1999), with the standard settings (when the headphone check fails: Stop the test; runs: 5). The main score was echo threshold (the delay at which the fitted curve gives half the pairs heard as two clicks).
ConductCognition versions: task version 1.0.0, scoring version 1.0.0. Every export records the versions each session used, for a methods section.
- Wallach, H., Newman, E. B., & Rosenzweig, M. R. (1949). The precedence effect in sound localization. The American Journal of Psychology, 62(3), 315-336. https://doi.org/10.2307/1418275The precedence effect: a first sound dominates where a sound and its quick echo are heard.
- Litovsky, R. Y., Colburn, H. S., Yost, W. A., & Guzman, S. J. (1999). The precedence effect. The Journal of the Acoustical Society of America, 106(4), 1633-1654. https://doi.org/10.1121/1.427914Review of fusion, localization dominance and discrimination suppression.
- Brown, A. D., & Stecker, G. C. (2013). The precedence effect: Fusion and lateralization measures for headphone stimuli lateralized by interaural time and level differences. The Journal of the Acoustical Society of America, 133(5), 2883-2898. https://doi.org/10.1121/1.4796113Lead and lag clicks over headphones, placed by a difference in arrival time, reported as one or two sounds and where.
- Bianchi, F., Verhulst, S., & Dau, T. (2013). Experimental evidence for a cochlear source of the precedence effect. Journal of the Association for Research in Otolaryngology, 14(5), 767-779. https://doi.org/10.1007/s10162-013-0406-zOne click or two over headphones, and echo thresholds of a few milliseconds for clicks.
- Freyman, R. L., Clifton, R. K., & Litovsky, R. Y. (1991). Dynamic processes in the precedence effect. The Journal of the Acoustical Society of America, 90(2), 874-884. https://doi.org/10.1121/1.401955A train of earlier clicks raises the echo threshold, so each pair here comes alone.
- Woods, K. J. P., Siegel, M. H., Traer, J., & McDermott, J. H. (2017). Headphone screening to facilitate web-based auditory experiments. Attention, Perception, & Psychophysics, 79(7), 2064-2072. https://doi.org/10.3758/s13414-017-1361-2The headphone check before the test.
Source papers
- Litovsky, Colburn, Yost and Guzman (1999): fusion, localization dominance and discrimination suppression. Brown and Stecker (2013): one or two sounds and their place, for lead and lag clicks over headphones.Paradigm source, Adults
Questions
How long does the Precedence Effect Task take?
About 6 to 9 minutes, as listed in the test library.
What device does a participant need?
Untimed test: runs on desktops, laptops, tablets and phones. Needs headphones. The browser must be Chrome, Edge, Firefox or Safari.
What scores does it produce?
Echo Threshold, Two Clicks by Delay, Lead Dominance, Fused Share, Single Click Side, Single Clicks Heard as Two, Median Answer Time, Anticipations, Completed Trials, Planned Trials, Headphone Check Passed, Headphone Check Correct and Reported Output Delay. Each session is also marked valid, needs review or invalid, with the reason.
How widely is the Precedence Effect Task used in research?
58 papers from 2021 to 2025 name it in their title or abstract, down 33% compared with 2016 to 2020. That ranks it 287 of 495 test families in the ConductCognition test census (use grade D). Source: ConductCognition test census 0.22.0, counted 3 November 2026 from OpenAlex and ClinicalTrials.gov.
How much reliability evidence does the Precedence Effect Task have?
In the published research, 0 papers report its test-retest reliability and 1 registered clinical study uses it as an outcome (evidence grade D in the ConductCognition test census).
Does it report a percentile?
No. Scores and quality flags only.
Which settings can a researcher change?
When the headphone check fails (Stop the test, Continue the test) and runs (3 to 8). 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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