Abstract: This is an experimental study on the observation of light signal presented at different directions. The results indicated:1. By giving a preparatory signal to the Ss a few seconds before the stimulus ap pears, the reaction time in observation were shortened greatly.2. Observations accompanied with oral counting the beats of a metronome showed no influence on the reaction time.3. The reaction time increased when Ss observed with monocular vision than with binocular vision. The reaction time and mistakes increased when Ss observed with right eye observing (with left eye blindfold) at the light presented the left direction and vice versa.4. When Ss observed in a supine position and prone position, light in frontal direction were most easily discovered, especially those in the left-frontal direction. There were no significant difference between the reaction time in observing the stimuli from the left and from the right. The most difficult stimuli to react were those appearing at the back direction, especially the mid-back direction.5. When the Ss were in a supine position, the stimuli appearing at the front, left and right directions were most easily discovered in the middle region, then those in the lower region, and the stimuli in the upper region seemed to be more difficult to discover. While at the back direction, reaction time to stimuli in upper, middle and lower regions yielded no significant difference. When the Ss were in a prone position, stimuli from the frontal direction were easily discovered in the upper region, and also from the left and right directions in the middle region. There were no significant difference in the upper, middle and lower regions from the back direction.6. When Ss observed with monocular vision or observed in a supine position and prone position, stimuli in frontal direction were most easily discovered, then those in the left and right direction. The most difficult stimuli to observe were those appearing in the back direction.

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