Wednesday, September 12, 2007

Limits on human bandwidth

Along the lines of the "Rules of Thumb" posts:

I won't claim that the internet has changed nothing. It's at least changed how far and how fast news travels, and this has a number of subtle and unsubtle effects. But no matter how fast the network, storage and processors, as long as people are using the web there will be certain hard limits. Some that come to mind:

How much information can a person absorb?

If we're talking about raw sensory input, which appears to be dominated by sight and (to a lesser extent) sound, then my guess is that HD video comes pretty close to the limit. That's on the order of 20Mbit/s, or 10GB/hour, 250GB/day or 100TB/year. I'm taking the MPEG compressed rate as opposed to the raw frame rate as that more closely represents what the visual system is really processing (because successful lossy video compression is finely tuned to the way the visual system works)

Given that disk capacity increases about 100-fold every decade, in ten years one could reasonably afford to buy enough storage to store a fairly immersive audio/video stream that would take a year, 24/7, to watch. Taking time out for things like, um, sleeping and eating, it would probably be more like two or three years.

Conversely, if you wanted to record everything you saw and heard, you could do it for a reasonable -- and decreasing -- annual cost in the not-too-distant future. Anyone could do it, unobtrusively. "Be careful, his bowtie is really a camera".

If you want to boil that raw content to the more abstract images stored in the rest of the brain, there's a pretty well-established medium that covers that reasonably well, though not perfectly: words and pictures. It's trivial now to store all the words a person could reasonably process or produce in a lifetime, or even every mouse click or keypress, timestamped to, say, the nearest millisecond.

A picture on disk is probably worth more like hundreds of thousands of words, but storing tens of thousands of pictures is no big deal these days, either. That's a lot of pictures, if you want to take the time to look a them.

In short, when it comes to words and pictures, the limitation is not what the computer can handle but what the people using it can handle. Audio and video are rapidly approaching the same state.

How many people can a person keep in touch with?

With modern technology, I can now keep in touch with people all over the world, but I can't keep in touch with any more people than I ever could. Somehow the advent of the internet didn't add any new hours to the day. I don't have objective numbers handy on how many people people interact with, though I'm sure there are studies on the subject. At a guess, I'd expect the usual log-normal distribution, with a handful of people accounting for most of a typical person's interactions and maybe a few dozen accounting for almost all of it.

Balancing that is the small world property of social networks and many other structures, including the web itself. In such cases the degree of separation between any two individuals grows very slowly, if at all, as the network expands. In the movie version, there are no more than six degrees of separation between any two people. The actual number (neglecting any groups that really are totally isolated) is probably larger but not much larger. [See these later posts for a bit more on the topic]

How quickly can a group reach consensus?

Whether it's everyone deciding that magenta is the new chartreuse or a deliberative body deciding that the bylaws should be amended to allow for amendments to amendments, the game has probably not changed appreciably in recorded history.

In the mass-consensus case of global pop culture, the scope is bigger, but one of the "small world network" results is that both the average person's view of the social network and the overall structure of the network itself change little as the network grows. In other words, fashions in the malls of the world are driven by the same basic forces as those in, say, Louis XV's France or Julius Caesar's Rome, just on a bigger scale.

In the small-scale case of a deliberative group, the limiting factor is how quickly the members can get the others to understand and (ideally) accept their view of the world. Again, it seems to matter little whether the members are sitting around a campfire or exchanging messages electronically.

I do find it interesting that most of the distributed groups I've been involved with develop a mix of email, live conferencing and face-to-face meetings. Most of the routine stuff can be worked out via email, sometimes you have to pick up the phone and talk to a particular person, and every so often you should all meet. Most of those meetings can be by phone/IRC, but a few of them should have everyone sitting in the same room. It'll be a while yet before technology can completely replace this.

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