Study protocol and lighting control strategy
alertness
Before the study started, a randomization list was generated (Subjects entered the test room illuminated with standard lighting (see Table In each test cycle, the psychometric tests (performance tests and questionnaires) were performed on the computer, and the light interventions were automatically started by a computer program. In this way, the contact time between the study administrator and the study participants was minimized and the start of the light intervention and the psychometric measurements were synchronized.In each test cycle, subjects were initially exposed to standard lighting for 25 min. During this time, they were allowed to read available newspapers and magazines, were instructed to keep their eyes open, and could see a clock on the screen counting the time to the start of the upcoming psychometric test. After 25 min, subjects first rated their state of alertness (VAS), and then the aPVT began. After 5 min, while the aPVT was performed in a highly concentrated manner, the task lighting automatically switched to one light intervention setting. Study participants continued with the aPVT for an additional 10 min.Ten minutes after the start of the two light interventions, the aPVT ended and subjects reassessed their alertness state (VAS). Then, the complex attention test (GNT) started automatically. In the first light pulse condition, this test was performed under bright light exposure (1360 lx at eye level) whereas in the second light pulse condition, the test was performed under standard task lighting (130 lx at eye level).After completion of the GNT, study participants rated their affective state (PANAS) and workload (NASA TLX) under the two different corneal illuminance levels. Then, the illuminance under the stronger light pulse condition was dimmed to standard illumination (130 lx at eye level) for a period of 1 min, and the 1-h test cycle ended.Subjects run through five test cycles on each of the two subsequent study days (Fig. Timeline of the entire experiment. R, different rating scales; aPVT, auditory psychomotor vigilance task; GNT, go/no-go task.To minimize the influence of daylight light exposure, the study began in the early morning (07:00 AM), and subjects were instructed to wear sunglasses outdoors the day before the study began and in the afternoon between the first and second study day.The study protocol and light control strategies within a test cycle are shown in Fig. Study protocol and lighting control strategies within the 1-h test cycle. aPVT, auditory psychomotor vigilance task; GNT, go/no-go task; VAS, visual analog scale; PANAS, positive and negative affect scale; TLX, NASA task load.