Motion blur is caused by the image of the thing moving on your retina. Humans are very good at tracking steady movement with their eyes ("smooth pursuit"). When

Motion blur is caused by the image of the thing moving on your retina. Humans are very good at tracking steady movement with their eyes ("smooth pursuit"). When you're successfully tracking something this way the image is steady on your retina and there's no motion blur on it, only on the background. Applying motion blur relative to the camera does not look the same because it doesn't react to your eye movement. Synthetic motion blur (baked into the image and visible even with static images) can be used to partly hide low framerate, and with games it would be theoretically possible to use eye tracking to show synthetic motion blur relative to eye movement, but movies have to show the same thing to everybody. The only option for realism is to increase the framerate and rely on real motion blur. 120fps is about the minimum you can get away with for this and still have it look somewhat convincing. Trumbull's Showscan tests were with untrained audiences, they didn't know what to look for. With the right test signals and trained viewers you can see differences in frame rate well into the kilohertz by examining the interaction with eye movement.