Night work, circadian rhythm, and cognitive performance: A field study with airport security screeners

The effects of circadian rhythms and night work on performance have been extensively studied using standardized, non-work-related tasks in laboratory settings. However, field research on work performance is scarce in this domain. This study addresses this gap by analyzing four million behavioral responses from 1437 security officers at an international airport. We compared threat detection performance during the routine security screening of passengers' baggage X-ray images across night shifts (shift starting between 0:00 and 2:59), early morning shifts (starting between 3:00 and 5:59), and standard morning shifts (starting between 6:00 and 7:59). Processing times followed the circadian rhythm of attention found in laboratory studies, indicating that the rhythm affects real-life work performance. False alarm rates (i.e. false target present responses) were slightly higher during night and early morning shifts than during standard morning shifts, with no significant difference in the security-relevant hit rates (i.e. true target present responses). Furthermore, we found no performance differences between night work and early morning shifts, suggesting that both can disrupt employees’ natural sleep patterns with implications on performance.