Non-image forming effects of illuminance level: Exploring parallel effects on physiological arousal and task performance

The results revealed significant improvements in performance on the BDST difficult trials under 1700 lx vs. 165 lx (p = 0.01), while illuminance level did not affect performance on the PVT and BDST easy trials. Illuminance level impacted HR and SCL, but not SBP. In the afternoon sessions, HR was significantly higher under 1700 lx vs. 165 lx during PVT performance (p = 0.05), while during BDST performance, HR was only slightly higher under 600 vs. 165 lx (p = 0.06). SCL was significantly higher under 1700 lx vs. 165 lx during performance on BDST easy trials (p = 0.02) and showed similar, but nonsignificant trends during the PVT and BDST difficult trials. Although both physiology and performance were affected by illuminance level, no consistent pattern emerged with respect to parallel changes in physiology and performance. Rather, physiology and performance seemed to be affected independently, via unique pathways.