Circadian Timing and Time Perception in Healthy Adults (ChronoTime)

How Do Individual Differences in Circadian Rhythms Influence Time Perception?

This study examines how a person's natural daily rhythm ("chronotype") affects the way time is experienced and judged. Healthy Danish-speaking adults (23-45 years) who are clearly morning-type or evening-type will complete two lab sessions in a crossover design: one at their preferred time of day (e.g., morning for morning-types) and one at the opposite time (misaligned). In each session, participants do brief computerized tasks that measure time estimation/production, vigilance (psychomotor vigilance task), decision-making, and responses to social information, plus simple color-vision tasks. Short questionnaires about sleepiness, mood, fatigue, and the subjective "passage of time" are collected before, during, and after testing. A subset will wear a wrist actigraphy device for one week beforehand to characterize sleep-wake patterns.

Testing is conducted under standardized lab conditions with scheduled breaks. The main goal is to determine whether time judgments and vigilance are less accurate during the misaligned session and whether decision-making and social responses also vary with circadian timing. Risks are minimal and mainly relate to temporary tiredness when tested at a non-preferred time; participants may stop at any time. Participation is voluntary. Data are pseudonymized and handled under GDPR. Participants receive DKK 300 after completing both sessions (pro-rated if they withdraw early). Results will be published regardless of outcome, and de-identified data/code will be shared after publication.This study examines how a person's natural daily rhythm ("chronotype") affects the way time is experienced and judged. Healthy Danish-speaking adults (23-45 years) who are clearly morning-type or evening-type will complete two lab sessions in a crossover design: one at their preferred time of day (e.g., morning for morning-types) and one at the opposite time (misaligned). In each session, participants do brief computerized tasks that measure time estimation/production, vigilance (psychomotor vigilance task), decision-making, and responses to social information, plus simple color-vision tasks. Short questionnaires about sleepiness, mood, fatigue, and the subjective "passage of time" are collected before, during, and after testing. A subset will wear a wrist actigraphy device for one week beforehand to characterize sleep-wake patterns.

Testing is conducted under standardized lab conditions with scheduled breaks. The main goal is to determine whether time judgments and vigilance are less accurate during the misaligned session and whether decision-making and social responses also vary with circadian timing. Risks are minimal and mainly relate to temporary tiredness when tested at a non-preferred time; participants may stop at any time. Participation is voluntary. Data are pseudonymized and handled under GDPR. Participants receive DKK 300 after completing both sessions (pro-rated if they withdraw early). Results will be published regardless of outcome, and de-identified data/code will be shared after publication.

Study Overview

• Status: Recruiting
• Conditions: Circadian Rhythm; Time Perception
• Intervention / Treatment: Behavioral: Session timing relative to chronotype

Detailed Description

Background/Rationale. Circadian rhythms vary across individuals (chronotypes) and can be misaligned with social schedules. Both circadian timing and time perception influence cognition and behavior, yet within-person effects of circadian alignment on temporal judgments and related functions are not well characterized.

Objectives/Hypotheses. Primary: test whether circadian misalignment (testing at a non-preferred time) increases time-estimation/production bias and reduces vigilance versus aligned testing. Secondary: assess effects on temporal variability, duration discrimination, decision-making strategies, social conformity, and simple color-perception measures (white-point/unique-hue).

Design. Randomized, two-condition crossover trial with within-subject comparison of circadian-congruent vs incongruent sessions (order counterbalanced). Sessions occur on the same day (morning and evening) with a substantial break; no visible clocks; caffeine/exercise restrictions prior to testing. A subset (n≈60) completes 7-day actigraphy and sleep diary.

Participants. Healthy adults, 23-45 years, Danish-speaking, clear morning or evening chronotype (MEQ/MCTQ). Key exclusions: shift work, recent trans-meridian travel, sleep/neurologic/psychiatric disorders, medications affecting sleep/cognition, intermediate chronotype.

Intervention. Behavioral manipulation of testing time relative to chronotype (congruent vs incongruent) in a crossover design.

Outcomes.

Primary: (1) Time-estimation/production bias across 10-60 s targets; (2) Psychomotor vigilance task (lapses, RT).

Secondary: Time-estimation variability (CV), duration discrimination threshold, passage-of-time ratings, KSS sleepiness, mood/fatigue scales, information-conformity effect, decision-making metrics, color-perception indices (white-point/unique-hue).

Outcome time frame: per session; within-subject contrast (incongruent-congruent).

Sample size/Analysis. Target N≈128. Within-subject models test condition effects, with chronotype and session order as factors; missing data handled with mixed-effects models. Alpha=0.05 (two-sided).

Data management/Sharing. Pseudonymized data stored per AU policy/GDPR. De-identified datasets and analysis code will be shared in an open repository within 12 months of primary publication.

Risk/Benefit. Minimal risk (temporary tiredness). Potential benefits include improved understanding of circadian influences on cognition with implications for scheduling and performance.

• Study Type: Interventional
• Enrollment (Estimated): 128
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Cehao Yu, PhD; Email: cehao.yu@psy.au.dk
• Study Contact Backup: Name: Ali Amidi, PhD; Phone Number: +45 87165305; Email: ali@psy.au.dk

Study Locations

• Denmark
  • Aarhus, Denmark, 8000
    • Recruiting
    • Cognition and Behavior Lab
    • Contact: Mette Hejberg Pedersen; Phone Number: +45 9350 8899; Email: cobelab@au.dk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Aged 23 to 45 years
• Able to understand and communicate in Danish
• Completed at least upper secondary education (e.g., gymnasium)

• Categorized as either a Morning Type (MT) or Evening Type (ET) based on standardized chronotype assessments:

  • Munich Chronotype Questionnaire (MCTQ):

    • MT: sleep midpoint on free days (MSFsc) ≤ 03:00
    • ET: sleep midpoint on free days (MSFsc) ≥ 05:00

  • Morningness-Eveningness Questionnaire (MEQ):

    • One of four defined chronotype categories (definitely morning, moderately morning, moderately evening, definitely evening).

Exclusion Criteria:

• Current engagement in shift work, rotating schedules, or other forms of irregular sleep-wake timing
• Diagnosis of any neurological, psychiatric, or sleep-related disorder (e.g., insomnia, narcolepsy, sleep apnea)
• Use of medications that affect sleep, alertness, or circadian functioning (e.g., melatonin, stimulants, antidepressants)
• International travel across time zones within the four weeks preceding study participation
• Are classified as having an intermediate chronotype based on validated chronotype assessments (MCTQ or MEQ), as this group does not provide the necessary contrast to evaluate circadian alignment effects.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Sequence AB - Congruent → Incongruent; rossover sequence AB. Participants first complete a circadian-congruent session (morning types in the morning; evening types in the evening), followed by a circadian-incongruent session (opposite time). Intervention administered: Behavioral - Session timing relative to chronotype.	Behavioral: Session timing relative to chronotype; Two-period, two-sequence crossover manipulation of testing time. Each participant completes both sessions: (1) circadian-congruent timing (morning types tested in the morning; evening types in the evening) and (2) circadian-incongruent timing (opposite time). Session order is randomized (AB/BA). Sessions are run morning and evening on the same day with a substantial interval; no visible clocks; 12-h pre-session caffeine/strenuous-exercise restriction; standardized lab light/temperature. Primary outcomes: time-estimation/production bias and PVT lapses/RT.; Other Names: Circadian alignment; Circadian misalignment; Timing condition
Experimental: Sequence BA - Incongruent → Congruent; Crossover sequence BA. Participants first complete a circadian-incongruent session (opposite of their preferred time), then a circadian-congruent session. Intervention administered: Behavioral - Session timing relative to chronotype.	Behavioral: Session timing relative to chronotype; Two-period, two-sequence crossover manipulation of testing time. Each participant completes both sessions: (1) circadian-congruent timing (morning types tested in the morning; evening types in the evening) and (2) circadian-incongruent timing (opposite time). Session order is randomized (AB/BA). Sessions are run morning and evening on the same day with a substantial interval; no visible clocks; 12-h pre-session caffeine/strenuous-exercise restriction; standardized lab light/temperature. Primary outcomes: time-estimation/production bias and PVT lapses/RT.; Other Names: Circadian alignment; Circadian misalignment; Timing condition

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Time estimation bias	Signed percent error across 10, 30, and 60 s trials with a fixation cross: ((estimated - target)/target) × 100. Three trials per duration; session-level mean computed. Primary contrast: incongruent - congruent (within-subject). Higher values = overestimation.	Day 1 (once during each of the two laboratory sessions: morning and evening)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Psychomotor Vigilance Task (PVT) lapses (count)	Number of lapses (reaction time > 500 ms) during a 10-minute PVT. Session-level count. Primary contrast: incongruent - congruent (within-subject). Secondary PVT metrics (median RT, 10% slowest RT) analyzed separately.	Day 1 (once during each of the two laboratory sessions: morning and evening)
Time production bias (neutral stimuli, 10-60 s)	Signed percent error for produced intervals vs targets (10, 30, 60 s). Three trials per duration; session-level mean. Contrast: incongruent - congruent (within-subject).	Day 1 (once during each of the two laboratory sessions: morning and evening)
Duration discrimination threshold (2AFC adaptive)	JND (ms or % of standard) from a 2-interval, 3-down/1-up staircase with sub-second to few-second standards; session-level threshold. Contrast: incongruent - congruent.	Day 1 (once during each of the two laboratory sessions: morning and evening)
Subjective passage-of-time rating (VAS 0-100)	VAS rating of "how fast time felt" collected pre/mid/post session; session-level mean or change from baseline. Contrast: incongruent - congruent.	Day 1 (pre-, mid-, and post-session ratings during each of the two laboratory sessions)
Decision-making exploration rate (%) - Alien Game	Percent exploratory choices and total reward in a computerized multi-armed task; session-level metrics. Contrast: incongruent - congruent.	Day 1 (once during each of the two laboratory sessions: morning and evening)
Social conformity effect (% shifts toward majority)	Proportion of responses shifted toward displayed majority opinion vs own baseline on perceptual judgments; session-level effect size. Contrast: incongruent - congruent.	Day 1 (once during each of the two laboratory sessions: morning and evening)

Collaborators and Investigators

• Sponsor: University of Aarhus

Study record dates

Study Major Dates

• Study Start (Actual): October 25, 2025
• Primary Completion (Estimated): April 30, 2027
• Study Completion (Estimated): June 30, 2027

Study Registration Dates

• First Submitted: November 14, 2025
• First Submitted That Met QC Criteria: December 5, 2025
• First Posted (Estimated): December 18, 2025

Study Record Updates

• Last Update Posted (Actual): December 22, 2025
• Last Update Submitted That Met QC Criteria: December 19, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Keywords: chronotype; circadian misalignment; time estimation; duration discrimination; time production
• Other Study ID Numbers: 1-10-72-108-25; 10.46540/4256-00108B (Other Grant/Funding Number: Independent Research Fund Denmark)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No