The research object is to investigate the effects of luminance level of the light source in the central vision on arousal level, attention and task performance. In this study two experiments were carried. The results are as follows: 1. Comparing to the environment without light, arousal and attention level become higher in the environment with light, but arousal level and attention are not influenced by luminance level on the range of 30 cd/m^2 to 1000 cd/m^2. 2. The performance of computer key-in task and letter detecting task become worse when the lighting environment changes from luminance level of 100 cd/m^2 to 8000 cd/m^2. However, short-term memory task is not influenced by the change of luminance level. Arousal and attention level increasecd when light is put into darkness. However, on the range of luminance level from 30 cd/m^2 to 1000 cd/m^2, arousal and attention level do not change when the level of brightness increases. 0n the contrary, legibility becomes worse, adaptation time becomes longer, and task performance worsens in over-bright environment.
