THE need for expanding computer memory and processing power is no longer debated because it has become clear that we all need more every year, and relatively speaking, they cost nothing anyway. A more nonsensical debate that refuses to die centres on the need for bandwidth.

This one relates, not just to the amount, but to the asymmetric or symmetric nature of traffic and the speed of the up and downstream connections. At the simplest level, the broadcast mindset says people will sit at a PC and download information in large quantities, and their output will be dominated by control information and short messages. Another mindset says that people will be both consumers and producers. So who is right? For sure, it is futile even to contemplate studying this one, because the outcome is now so obvious. Imagine an airport or train station where more planes, trains and people arrive than leave, or a place where people just listen and seldom talk. Yes, there are such places, but they are the exception, and usually associated with some crisis. Humans like to visit places and then return home, and they love to communicate and contribute actively.

Yes, orators have shouted into the crowd (narrowcast) for aeons with the hecklers responding in some humorous or other way, but the most productive human effort comes from debate and interaction. Moreover, the Internet environment is much more of a society than a passive place. It is where people go to explore, seek out and find as well as interact.

Our society seems blinkered by broadcast thinking. The future will be 50, no 500, no 5,000 digital TV channels into the home, cries the industry. The protagonists overlook two important factors. First: five channels of nothing is just as useful as 5,000 channels of nothing. Second: unlike television, computers demand our input, they are naturally interactive environments, it is impossible to be passive; if you do nothing, nothing happens.

Broadcast radio and TV invoke no sense of community - they just present a passive window into a predefined world - they just do it to you. In complete contrast, the first thing youngsters do on the Net when they discover something of interest, is broadcast it to all their friends. They automatically belong to a networked community, a place that is as rich as the people and their contributions. So in this context a typical pattern is one bit received and 10 bits broadcast - exactly the converse of the broadcaster's model, which is to receive millions of bits and do nothing. It is perhaps not surprising that young people are migrating from TV to computer, while keeping their total screen time approximately constant.

Email is obviously, more or less, symmetric, as are telephone calls, FAX, and video conferencing. But sending electronic holiday snaps to both sets of grandparents is not, and there is a desire to send video clips, again defying the broadcast model. Electronic commerce, banking, information services and many others seem to lie somewhere between hard symmetry and asymmetry. And how much symmetric bandwidth do we subconsciously desire? More than the industry can even imagine.

Peter Cochrane holds the Collier Chair for the Public Understanding of Science & Technology at the University of Bristol. His home page is:
http://cochrane.org.uk