Exactly what Camman said:(from Wikipeida) Time is often referred to as the "fourth dimension". It is, in essence, one way to measure physical change. It is perceived differently from the three spatial dimensions in that there is only one of it, and that movement seems to occur at a fixed rate and in one direction. 

 So basically we have been playing 4D games all along since we interact with the 3D objects on the screen. (the Sony statement was basically a marketing pitch)