Synchronicity

Each person has a window of time during which events seem simultaneous. This window, incidentally, is not the same for all senses. Click-fusion, or experience of simultaneity in audible clicks, will happen for any two stimuli less than .005 seconds apart (for normal people.) Two flashes of light, on the other hand, will appear simultaneous as far as .03 seconds apart. These windows grow larger with age.

More bizarre still is that our brain will alter our experience of simultaneity to match a visual cue with it's accompanying sound only up to a certain distance, and then, suddenly, the two will seem out of sync.

And, here is the real kicker, the brain unconsciously compensates for imposed time lags on simultaneity between the senses until they are perceptually invisible. In studies where subjects move a computer mouse, but the clicker on the screen moves only after a delay, subjects report that after a short period they stop experiencing a delay between their movement and that of the clicker. When the mouse and clicker are synced up again, these subjects, for a brief while, will have the bizarre experience of seeing the clicker move before their hand does. Obviously it isn't, but they feel as if it is.