Dale Ireland said, "The brain processes moving objects in some very interesting ways. For instance, this is one of my favorites... We ride the ferry boat quite often and I have tried this with quite a few people. When the ferry is underway if you stare at the horizon for a couple minutes, with the water surface waves and chop passing quickly through the lower half of your field of vision, and then abruptly turn and stare at a blank wall the lower half of your field of vision will have patterns moving through it for a few seconds like the water was. I think that is similar to the effect you were describing. I think jerky or wavy motions are nystagmus thoughfield of vision, and then abruptly turn and stare at a blank wall the lower half of your field of vision will have patterns moving through it for a few seconds like the water was. I think that is similar to the effect you were describing. I think jerky or wavy motions are nystagmus though." That illusion, called the Motion Aftereffect (Waterfall Illusion), is demonstrated here. http://www.michaelbach.de/ot/mot_adapt/index.html The saccadic movement of the eyes don't make an image appear to wander, but I suppose they may produce a jerkiness. During the time the saccade is occurring you see the last image sustained until you lock in on a new one. You can see this happen by looking at yourself in a mirror and looking first at one of your own eyes then the next. To you your eyes will not be seen to move yet you feel them do so! The eyes do slowly "drift" before a saccade brings them back in line. The only way I have ever seen evidence of the drift is when using a technique that utilizes an after-image/image combination. The after-image is seen to drift about over the "live" image. Tom ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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