World culture is dominated by film and television. The alleged need for streaming video and video-on-demand drives many technical efforts, typically to boost computer transmission. But the resulting increase in bandwidth chokes the 'last mile' of old telephone wire to each viewer. And all this technology still relies on the century-old discovery that repeated still pictures, presented at 24 frames a second or more, give most people the illusion of motion. Meanwhile, sensory psychology has moved on.

Daedalus points out that the human eye slides around a scene, and makes several jumps per second (saccades) in the process. With each jump, large changes go unnoticed. This 'change blindness' allows a watching computer to change the hair colour of a human figure during a saccade, or even to remove it entirely, without detection. A convincing moving image could be presented at only a few frames a second if the frames were made to coincide with the shifts of attention of the human visual system itself.

Cinema and digital cameras, of course, register 24 or more complete frames a second; but they are not the problem. DREADCO physiologists are discovering just how few frames, if chosen to change during a saccade or an eye movement, will be sufficient to give the illusion of continuous movement on a video screen. They are studying viewers' eyes to spot the moments of change blindness. With luck, everybody will react alike. If they do, a few well-chosen frames, certainly fewer than 24, should give the illusion of perfect movement.

But even if we are all different, the technique will still work. Each video screen will have a small camera that detects optical cues from the viewer. Such 'interactive systems' are already being tested. Instead of 24 or more complete frames a second, far fewer will do a much better job. Personal data will be relayed back to the junction where broadband video meets the 'last mile' of telephone wire. Final bandwidth, the bugbear of all video systems, will be minimized.

The new DREADCO technology will only work for computer-transmitted video; the old cinema will still need 24 frames a second. But even if audience members all make different saccade choices, we may have some in common. A computer-controlled projector could select its frames, or show only parts of them, saving wear on the film and enhancing the pleasure of the audience.