The Differential Effects Facing The Achromatic And The Colorful Stimuli In Near And Far Space

In daily life,all the animals,including the human beings,could receive all kinds of information,so that they can survive in the complex and volatile environment. Of all the information they got from the outside,80%come from the visual system.It is very important for human’s decision and behavior.To investigate the visual behavior,the researchers have divided the visual field surrounding one’s body into two parts:the peripersonal (near) and extrapersonal (far) space.The near space of the visual field represents the space within arm’s reach,and the field without arm’s reach belongs to the far space.the researches have foud that there exists two kinds of subsystems independently modulating and manipulating the visual behavior of the two space.It is known that the dorsal stream of the brain would be activated when the healthy participants takes into the tasks relating with the near space;and when they perform tasks concerning the far space,the ventral stream would produces larger activation. This is proposed by Weiss in1990.And another theory proposed by Previc,supposed that the dorsal stream accepts the message from parvocellular,and it is sensitive to the massage relating with luminance;on the other hand,the ventral stream accepts the message from parvocellular,and it is sensitive to luminance and corlor information.Based on these theories,we designed our experiments.The first experiment employed the white spot as the target, demanding the participant focusing the middle fixation,and click on the right position after the flash of the target. The target may appear at one of the32positions,and the volunteers should pay their full attention to the appearance.The same task should be presented in both far and near conditions.This experiment tried to discover if there is any difference between near and far,and the results revealed that the volunteers’reactions are a little better when it is presented in near versus far.So we can draw a conclusion that for the detection of the achromatic target,the result is better when the participants complish the task in the near space(have significant effect).The second experiment used the green spot as the target,intending to explore the participants’performance difference to the colorful target under two different spaces including the near and far.All the other conditions and procedure are same as the first experiment. We analysed the results and found that there is a difference of the visual behavior between the near and far space:the volunteers performed better when the task presented in far space versus near space,and they also performed differently on the target appeared at different space in the same distance.These two experiments have already revealed the difference between near and far concerning the color,but if there is difference between the two spaces relating the luminance is still unsolved.In order to find it out,we employed the third experiment. This experiment explored the spot which contains the same color but the different luminance with the background as the target,make the participant pointing out the correct circle it had been filled.The results have proved that there existed difference between near and far:the participant performed better in near versus far,and different from the first experiment,the eccentricity of the circles produced different results.In a conclusion,there is different subsystems independently modulating and manipulating the visual behavior of the near and far space.Our findings have expanded the previous research,and support the Weiss’s theory and hypophysis from the level of behavior experiments.