An article by Cormack, Blake and Hiris discusses their experiment concerning a moving object seen in the peripheral vesual field. When the display is in motion, against a textured background, foveally, it is easy to detect which direction the object (bar) is traveling. In the peripheras visual field, this is not true.
Cormack and colleagues found a number of interesting facts. One, the color of the bar made no difference in the illusion. Second, the bar can veer 90 degrees away from the direction seen foveally. These experiments have demonstrated important defferences between seeing foveally and peripherally. This study looks at the effects of a circular pattern and its travel lengths.
13 females and three males were subjects asked to participate in this experiment. Using the Eye Line Software under the control of a Macintosh computer, a background was created consisting of concentric circles covering the whole screen (figure 1). The smallest circle was colored red. The bar, positioned horizontally, moved at a 45 degree angle traveling 115mm in the Long trial and 90mm in the Short trial. The trials differed only in how far the bar traveled after crossing the red center. In both trials the rectangle, when traveling, covered the red circle completely. The subjects were approximately 700mm from the screen at the time they were testing. A fixation point, a gold star, was placed approximately 140mm from the red circle to the top face of the computer monitor. The participants were instructed to stare at the star during each trial so they could watch the bar peripherally. They watched each trial consecutively three times with one second delays. Afterwards, the subjects were to draw the pattern of which they saw. They were measured to find the misdirected visual motion in the peripheral visual field.
After the measurements were tallied I found that the Long trial created a stronger effect on the peripheral visual field than in the Short trial (figure 2). According to the subjects, the illusion in the Long trial seemed to create an S shape traveling completely around the red circle. Also in the Short trial, the same pattern was consistent, though, the top of the S went through the red circle instead of around it.
The difference between the trials occurred after the bars passed the circle, one traveled further than the other. If this is the case, how can the pattern make an S shape? Too, how can one bar travel completely over the red circle and one through it when in reality they follow the same pattern? The difference in trials took place after the center was passed the circle, yet the subjects claim the stimuli traveled around the circle. This difference effected what happened in the middle rather than the end.
Seeing through the Peripheral Visual Field has yet to be studied further. Why is our vision so distorted peripherally? Can you answer that?