Forty Winks

Things you dont think about involve thinking. Take, for example, sleep. It may be akin to "garbage collection," Marvin Minsky says.

I cant remember having done an interview where I get to address love, consciousness and sleep at the same time.

Well, I dont know anything about sleep.

Well, you made a comment in one of your chapters about the activity of sleeping, which I thought was interesting, to think of sleep as an activity.

One theory of sleep is that there is general sleep and R.E.M. [rapid-eye movement] sleep, which is the stage where youre dreaming. It looks like that has some connection with long-term memory. If you deprive people of that kind of sleep, then they dont remember much the next day. There are various theories about that. Thats becoming the standard theory now.

But if sleep is an activity, and the activity is some kind of process that goes on, what is it? What is that process?

It may be like garbage collection, where you have things in your memory but theyre not connected up to anything. The dream process may be some system that tries to find some meaning to little fragments and piece them together and make them into some kind of story. A lot of whats in the dream are wrong connections that get thrown away then.

That would be what a dream is, but how — what is the process of actually sleeping? What actually happens when you go to sleep?

The process comes from the brain stem, and it goes through four or five stages. I havent paid much attention to the details of this, but there is a 50-year-old theory that you go through about four stages of turning stuff off. Virtually all the animals have these mechanisms. They dont have much to do with the mind, so those old theories were more like physiological theories that youre turning things off.

So there is no good mental theory of how this garbage collection works. There are a few papers and books on it, but the dust hasnt settled.