Fatigued Teams: Night Work Impairs Team Performance and Cohesion

This study found clear degradation in team outcomes during night work, particularly during the circadian low. At this time of the night, team members exhibited diminished alertness and productivity, leading to poorer team performance and cohesion. As such, the circadian system played a crucial role in modulating team performance and cohesion. Additionally, cooperation and team dynamics eroded across the night, persisting beyond the circadian low. These findings highlight the vulnerability of teams working at night, especially in safety-critical industries where effective teamwork is essential. Statement of Significance Night-shift workers in safety-critical settings experience well-known impairments in alertness, yet the consequences of this biological vulnerability for teamwork have been largely overlooked. This study shows that team performance and cohesion decline markedly during the early-morning hours when the circadian system promotes sleep, revealing a critical window in which teams are most at risk of reduced effectiveness. Importantly, disruptions to cooperation and team interactions persisted beyond this period, indicating that fatigue had enduring effects on overall team functioning. These findings highlight the need to consider biological timing when planning overnight operations and encourage future work aimed at developing strategies to sustain cooperative team functioning during and after periods of high fatigue.