JB: I've very little use for the digital technology metaphor as related to the human body.

BROOKS: The fact that we use the technology as a metaphor for ourselves really locks us into the way we think. We think about human intelligence as these neurons with these electrical signals. When I was a kid the brain was a telephone switching network, then it became a digital computer, then it became a massively parallel digital computer. I'm sure there's a book out there now for kids that says the brain is the World Wide Web, and everything's cross linked.

JB: In 1964 we used to talk about the mind we all share, the global utilities network.

BROOKS: We get stuck in that mode. Everyone starts thinking in those terms. I go to interdisciplinary science conferences and neuroscientists get up and say the brain is a computer and thoughts are software, and this leads people astray, because we understand that technical thing very well, but something very different is happening. We're at a point now where we're limited by those metaphors.

JB: How do you get beyond thinking about it that way?

BROOKS: The best I can hope for is to get another metaphor that leads us further, but it won't be the ultimate one either. So no, in no sense do are we going to get to an absolute understanding.

JB: Do you have any hints as to what might be the way to go?

BROOKS: Inklings, but it's still a question - I don't have the answer. I don't know the next step. For the last 15 years I've been plodding along and doing things based on these metaphors - getting things distributed, and not having central control, and showing that we can really do stuff with that, we can build real systems. But there's probably something else that we're missing. That's the thing that puzzles me now and that I want to spend time figuring out. But I can't just sit and abstractly think about it. For me the thing I need to do is keep pushing and building on more complex systems, and then try to abstract out from that what is going on that makes those systems work or fail.

JB: Talk about what you're doing.

BROOKS: The central idea that I've been playing with for the last 12-15 years is that what we are and what biological systems are. It's not what's in the head, it's in their interaction with the world. You can't view it as the head, and the body hanging off the head, being directed by the brain, and the world being something else out there. It's a complete system, coupled together. This idea's been around a long time in various forms - Ross Ashby, in Design for Brain in the '50s - that's what the mathematics he was trying to develop was about. Putting that in the digital age has led to being able to get machines to do things with very little computation, frighteningly little computation, when we have our metaphors of digital computers. That we're claiming and showing that we can do things without lots of computation has gotten a lot of people upset, because it really is a mixture of computation and physics and placement in the world. Herb Simon talked about this back in Science of the Artificial, in 1966, or '68 - his ant walking along the beach. The complexity of the path that the ant takes is forced on it by the grains of sand, not by the ant's intelligence. And he says on the same page, the same is probably true of humans - the complexity of their behavior is largely determined by the environment. But then he veers off and does crypto-arithmetic puzzles as the key to intelligence.

What we've been able to do is build robots that operate in the world, and operate in unstructured environments, and do pretty well, because they use whatever structure there is in the world to get the tasks done. And the hypothesis is that that's largely what humans are; that humans are not the centralized controllers. We're trying to implement this, and see what sorts of behavior we can get. It's like Society of Mind, which is coming top-down, and we're coming bottom-up, building with pieces and actually putting them together.