An interventional study of Individually Calibrated Time Load Dual-back Task With Seated Rest in Mental Fatigue and Cognitive Performance, sponsored by DSW Ideis University. Not yet recruiting at 1 site in Poland. Open to participants aged 18 Years to 30 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-16.
Sponsored by DSW Ideis University · Not applicable, Interventional, and Basic science
This study will investigate whether heart activity and changes in the skin's ability to conduct electricity can help predict performance during a demanding computer task. These signals reflect how the body responds to mental effort. The main question is whether measurements taken at rest and near the beginning of the task help predict later accuracy, beyond information about sleep the previous night, current sleepiness, and initial task performance.
Healthy young adults will attend one visit lasting approximately 50-60 minutes. Participants will complete a questionnaire and wear sensors that record heart activity and skin responses. After a five-minute resting measurement, participants will learn a computer task involving letters and numbers. The task requires remembering the previous letter and deciding whether numbers are odd or even. A short calibration will adjust the presentation speed to each participant.
Participants will then perform the task for 16 minutes at the selected speed and rate their fatigue and the demands of the task. After these ratings, participants will rest quietly for five minutes and repeat the task for four minutes at the same speed.
The researchers will also examine how performance, fatigue, and body responses change during the task and after rest. The study is intended to improve understanding of sustained mental effort and is not a medical diagnostic assessment.
COG-PRED is a prospective, single-group laboratory study of cognitive performance during sustained mental effort. Subjective fatigue, autonomic responses, and task performance may change at different rates. The study will examine whether resting autonomic activity and early physiological responses provide information about subsequent performance beyond that available from sleep duration, sleepiness, and initial task accuracy. All participants will follow the same sequence of procedures, without randomization or a separate control group.
Cognitive load will be induced using a study-specific implementation of the Time Load Dual-back (TloadDback) task. Letters and digits will alternate on the screen. Participants will respond when a letter matches the preceding letter and withhold a response when it does not. For digits, participants will classify each number as odd or even. Responses will be made with the dominant hand, while the hand carrying the skin conductance electrodes remains supported.
Following familiarization, a shortened adaptive calibration will identify an individual presentation interval using a criterion of at least 85% weighted accuracy. Search blocks will contain 30 stimuli, and the selected interval will be checked in a separate 40-stimulus verification block. Calibration will last no longer than five minutes. Participants who do not obtain a verified interval will not proceed to the main task. Once verified, the interval will remain fixed throughout the main task and the post-rest task. Individual calibration adjusts task pace but does not assume identical subjective workload across participants.
Physiological recording will cover the resting measurement, task phases, and recovery period. Cardiac and skin conductance signals will be synchronized with stimulus and response events. Resting features will be derived from the final four minutes of the five-minute baseline. Early task responses will be characterized by changes from this baseline during the first four minutes of the main task.
Prespecified linear regression models will assess later task accuracy while accounting for initial accuracy. A reference model containing previous-night sleep duration, pretask sleepiness, and initial accuracy will be compared with an expanded model that additionally includes resting heart rate, heart rate variability, skin conductance, and their early task changes. Predictive performance will be assessed using 10-fold cross-validation at the participant level. Physiological information recorded after the prediction window will not be used as an early predictor.
Immediately after the main task, participants will rate mental fatigue and complete the six dimensions of the National Aeronautics and Space Administration Task Load Index (NASA-TLX), scored as an unweighted mean. These assessments will precede the full five-minute seated rest. Participants will then rate fatigue and perform a four-minute task with a new stimulus sequence at the same calibrated speed. The total interval between the main task and the post-rest task will be recorded.
Secondary analyses will describe performance and physiological changes over time and compare the final four minutes of the main task with the four-minute post-rest task. Relationships between autonomic recovery and changes in performance will be explored separately. Because there is no no-rest control condition, changes after the break will not be interpreted as effects attributable solely to rest.
159 studies on the registry are indexed under Mental Fatigue; 55 are open to participants now.
This study's planned enrollment of 250 is above the median of 45 across 129 interventional studies indexed under Mental Fatigue.
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Participants undergo a five-minute seated baseline, task familiarization, and individual calibration of the Time Load Dual-back (TloadDback) task. After successful calibration, participants complete a 16-minute task combining letter matching with odd/even digit classification. Task pace remains fixed at the individually verified level. Immediately afterward, participants rate mental fatigue and perceived workload, followed by five full minutes of seated rest. Participants then rate fatigue and complete a four-minute post-rest task at the same pace, followed by final fatigue and well-being ratings. Cardiac activity and skin conductance are recorded throughout the measurement phases.
Behavioral: Individually Calibrated Time Load Dual-back Task With Seated Rest
Participants perform the Time Load Dual-back task, alternating letter 1-back matching with odd/even digit classification. A study-specific adaptive calibration starts at 1400 ms and tests presentation intervals between 400 and 1600 ms. Search blocks contain 30 stimuli; the selected interval must achieve at least 85% weighted accuracy in a separate 40-stimulus verification block. Calibration is limited to five minutes; participants without a verified interval do not proceed to the main task. The verified interval is used for a 16-minute main task and a four-minute post-rest task. Fatigue and workload ratings follow the main task, before five full minutes of quiet seated rest. A fatigue rating precedes the post-rest task. Task pace remains fixed after calibration.
Weighted Accuracy During the Final Four Minutes of the Main Cognitive Task
Weighted accuracy (WAcc) on the Time Load Dual-back task is calculated as 0.65 x letter accuracy + 0.35 x digit accuracy, with both component accuracies expressed as percentages. Letter accuracy includes correct responses to matching letters and correct withholding of responses to nonmatching letters. Digit accuracy is the percentage of correct odd/even classifications. Errors and required-response omissions are scored as incorrect. The first letter of each new sequence and technically excluded trials are removed from the relevant denominators; analytical windows do not reset the letter reference. Scores range from 0 to 100%, with higher scores indicating better performance. The primary endpoint is the late-task score; initial accuracy is included as a predictor, rather than subtracted to define this endpoint.
Time frame: During seconds 720-960 (the final four minutes) of the 16-minute main task, within a single study visit.
Weighted Accuracy Across the Main Cognitive Task
Weighted accuracy is calculated separately for each consecutive four-minute window as 0.65 x percentage letter accuracy + 0.35 x percentage digit accuracy. Correct letter responses include both target detections and correct withholding on non-target trials. The scoring and exclusion rules are identical to those for the primary outcome. Scores range from 0 to 100%, with higher scores indicating better performance. The repeated scores describe the course of performance during sustained cognitive load.
Time frame: During four consecutive 4-minute windows (0-240, 240-480, 480-720, and 720-960 seconds) of the 16-minute main task.
Change in Weighted Accuracy From the End of the Main Task to the Post-Rest Task
Weighted accuracy during the entire four-minute post-rest task minus weighted accuracy during the final four minutes of the main task, expressed in percentage points. Both scores use the same weighting (0.65 x letter accuracy + 0.35 x digit accuracy), scoring rules, and individually calibrated presentation interval. The difference ranges from -100 to +100 percentage points. Positive values indicate better accuracy after rest. This comparison describes change after the break without attributing the change solely to rest.
Time frame: During the entire 4-minute task after five minutes of seated rest; compared with seconds 720-960 of the 16-minute main task.
Median Correct-Response Reaction Time Across Task Phases
Within-participant median time from stimulus onset to the first keypress on a correctly scored response-required trial, in milliseconds, calculated separately for each assessment window. Only correct trials requiring a response are included; correct withholding on non-target letter trials has no reaction time. Responses earlier than 100 ms and technically excluded trials are not included. Response times must fall within the stimulus response window. Main-task trajectories and post-rest versus late-main-task values will be compared. Shorter times indicate faster responses and will be interpreted together with accuracy.
Time frame: During each of four consecutive 4-minute windows of the 16-minute main task and during the entire 4-minute post-rest task, within one visit.
Standard Deviation of Correct-Response Reaction Time Across Task Phases
Within-participant sample standard deviation of correct-response reaction times, in milliseconds, calculated separately for each assessment window. The same eligible responses are used as for median correct-response reaction time: correct keypresses from 100 ms after stimulus onset to the end of the response window. Correct withholding, anticipations, incorrect responses, and technically excluded trials are not included. Higher values indicate greater variability in response speed. Main-task trajectories and post-rest versus late-main-task values will be compared.
Time frame: During each of four consecutive 4-minute windows of the 16-minute main task and during the entire 4-minute post-rest task, within one visit.
Number of Incorrect Responses Across Task Phases
Number of trials with an incorrect keypress in each assessment window, including responses to non-target letters, incorrect response keys on letter-target or digit trials, and anticipatory responses earlier than 100 ms. A trial is scored once according to the first-keypress rule. Required-response trials without a keypress are counted separately as omissions; correct withholding on non-target letters is not an error. Technically excluded trials and the first reference-setting letter of each sequence are omitted. Counts will be interpreted with the number of eligible trials, which varies with the calibrated presentation interval. Lower counts indicate fewer incorrect responses.
Time frame: During each of four consecutive 4-minute windows of the 16-minute main task and during the entire 4-minute post-rest task, within one visit.
Number of Required-Response Omissions Across Task Phases
Number of letter-target and digit trials in which no keypress is recorded within the response window. Correct withholding on non-target letter trials is not an omission. Trials with anticipatory or incorrect keypresses are classified as incorrect responses rather than omissions. Technically excluded trials and the first reference-setting letter of each sequence are omitted. Counts will be interpreted with the number of eligible response-required trials. Main-task trajectories and post-rest versus late-main-task values will be compared. Lower counts indicate fewer omissions.
Time frame: During each of four consecutive 4-minute windows of the 16-minute main task and during the entire 4-minute post-rest task, within one visit.
Self-Reported Mental Fatigue Across the Study Visit
Single-item rating of current mental fatigue from 0 (no mental fatigue) to 100 (extreme mental fatigue). Ratings are obtained before baseline, after calibration immediately before the main task, immediately after the main task, after the full five-minute rest before the post-rest task, and after the post-rest task. Repeated ratings describe fatigue during preparation, sustained task performance, rest, and task resumption. Higher scores indicate greater fatigue.
Time frame: Before baseline; after calibration/before the main task; immediately after the 16-minute main task; after five minutes of rest/before the post-rest task; and immediately after the 4-minute post-rest task, within one visit.
Perceived Workload on the Unweighted NASA Task Load Index
Unweighted mean of the six ratings on the National Aeronautics and Space Administration Task Load Index (NASA-TLX): mental demand, physical demand, temporal demand, performance, effort, and frustration. Each dimension is scored from 0 to 100. The performance dimension is oriented from success to failure so that higher values on every dimension indicate greater workload or a less favorable assessment. The overall score ranges from 0 to 100, with higher scores indicating greater perceived workload. Ratings refer only to the 16-minute main task. Pairwise weighting is not used.
Time frame: Immediately after the 16-minute main task and before the start of the five-minute seated rest.
Heart Rate Variability During Baseline, Cognitive Load, and Rest
Root mean square of successive differences between normal-to-normal heartbeat intervals (RMSSD), in milliseconds, calculated from quality-controlled electrocardiographic recordings using continuous valid segments. Values are calculated separately for each assessment window. The natural logarithm of RMSSD is used in the predictive model; early reactivity is the first main-task window minus baseline on that logarithmic scale. Resting recovery compares the final four minutes of seated rest with the final four minutes of the main task and baseline. Higher RMSSD indicates greater successive-interval variability, without implying better cognitive performance.
Time frame: During seconds 60-300 of the 5-minute baseline, each consecutive 4-minute window of the 16-minute main task, and seconds 60-300 of the 5-minute seated rest.
Mean Skin Conductance During Baseline, Cognitive Load, and Rest
Mean skin conductance, in microsiemens, calculated from valid electrodermal samples in each assessment window. This measure includes both tonic level and contributions from phasic responses; it is not a decomposed tonic-only measure. The predictive model uses ln(1 + the numerical skin conductance value in microsiemens), with early reactivity calculated as the first main-task window minus baseline on this scale. Resting recovery compares the final four minutes of seated rest with the final four minutes of the main task and baseline. Higher values indicate greater skin conductance, without implying better or worse cognitive performance. The first minute of rest is additionally examined to describe the initial transition.
Time frame: During seconds 60-300 of baseline, each consecutive 4-minute window of the 16-minute main task, and the 5-minute rest (initial 60 seconds and final 240 seconds).
Heart Rate During the Post-Rest Cognitive Task
Mean heart rate, in beats per minute, derived from quality-controlled electrocardiographic data during the four-minute post-rest task. The value is compared with the final four minutes of the main task to explore the autonomic response during task resumption at the same calibrated presentation interval.
Time frame: During the entire 4-minute task after five minutes of seated rest; compared with seconds 720-960 of the 16-minute main task.
Heart Rate Variability During the Post-Rest Cognitive Task
Root mean square of successive differences between normal-to-normal heartbeat intervals (RMSSD), in milliseconds, calculated from continuous valid segments of the electrocardiographic recording during the four-minute post-rest task. The value is compared with the final four minutes of the main task to explore the autonomic response during task resumption.
Time frame: During the entire 4-minute task after five minutes of seated rest; compared with seconds 720-960 of the 16-minute main task.
Skin Conductance During the Post-Rest Cognitive Task
Mean skin conductance, in microsiemens, calculated from valid electrodermal samples during the four-minute post-rest task. The value is compared with the final four minutes of the main task to explore the autonomic response during task resumption. The measure includes tonic level and contributions from phasic responses.
Time frame: During the entire 4-minute task after five minutes of seated rest; compared with seconds 720-960 of the 16-minute main task.
Individually Verified Stimulus Presentation Interval
Stimulus presentation interval accepted after successful calibration of the Time Load Dual-back task, in milliseconds. Permitted values range from 400 to 1600 ms in 100-ms increments. The interval must satisfy the weighted-accuracy criterion in a separate verification block and is then fixed for both the main and post-rest tasks. Lower values indicate a faster task pace, not an intelligence score. This measure is used in supplementary analyses; no interval is assigned if calibration is unsuccessful.
Time frame: At successful completion of the adaptive calibration, which lasts no longer than five minutes and precedes the 16-minute main task.
Standard Deviation of Normal-to-Normal Heartbeat Intervals
Standard deviation of normal-to-normal heartbeat intervals (SDNN), in milliseconds, derived from quality-controlled electrocardiographic data. This supplementary measure is calculated separately within the four-minute physiological assessment windows. Higher values indicate greater overall heartbeat-interval variability within the window. SDNN is supplementary to the prespecified RMSSD measure and is not substituted for RMSSD in the primary predictive model.
Time frame: During seconds 60-300 of baseline, each consecutive 4-minute window of the 16-minute main task, seconds 60-300 of seated rest, and the entire 4-minute post-rest task.
Plan to share: Yes — De-identified individual participant data underlying the results reported in each publication will be made publicly available as supplementary data accompanying that publication. Shared datasets will contain the relevant participant-level behavioral, questionnaire, and derived physiological measures, together with a data dictionary. Direct identifiers and raw physiological recordings will not be included. Datasets will undergo a review of re-identification risk before release.
Supporting information: Study protocol, Statistical analysis plan, Analytic code
Time frame: Upon publication of each corresponding article, with no planned end date.
Access criteria: Public access through the supplementary materials accompanying each publication, without an individual access request.
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