Fig. 1.

Mean subjective score for low workload level (LWL) and high workload level (HWL) with standard error as error bar (±1SE) a and b for control and experimental groups, respectively. C1 Pre-control group at 0-day time period, C2 post-control group after 30 days period, E1 pre-experimental group prior exposure to SKY, E2 post-experimental group after 30 days period, E3 post-experimental group after 90 days period. 0-day time period was defined as the time period prior to experiment beginning