Circadian Timing and Time Perception in Healthy Adults

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.