BEYOND COMPUTATION: A TALK WITH RODNEY BROOKS

So, my mid-life research crisis has been to scale down looking at humanoid robots and to start looking at the very simple question of what makes something alive, and what the organizing principles are that go on inside living systems. We're coming at it with two and a half or three prongs. At one level we're trying to build robots that have properties of living systems that robots haven't had before. We're trying to build robots that can repair themselves, that can reproduce (although we're a long way from self-reproduction), that have metabolism, and that have to go out and seek energy to maintain themselves. We're trying to design robots that are not built out of silicon steel, but out of materials that are not as rigid or as regular as traditional materials—that are more like what we're built out of. Our theme phrase is that we're going to build a robot out of Jello. We don't really mean we're actually going to use Jello, but that's the image we have in our mind. We are trying to figure out how we could build a robot out of "mushy" stuff and still have it be a robot that interacts in the world.

The second direction we're going is building large-scale computational experiments. People might call them simulations, but since we're not necessarily simulating anything real I prefer to call them experiments. We're looking at a range of questions on living systems. One student, for example, is looking at how multi-cellular reproduction can arise from single-cell reproduction. When you step back a little bit you can understand how single-cell reproduction works, but then how did that turn into multi-cellular reproduction, which at one level of organization looks very different from what's happening in the single-cell reproduction. In single-cell reproduction one thing gets bigger and then just breaks into two; in multicell reproduction you're actually building different sorts of cells. This is important in speculating about the pre-biotic emergence of self-organization in the soup of chemicals that used to be Earth. We're trying to figure out how self-organization occured, and how it bootstraped Darwinian evolution, DNA, etc. out of that. The current dogma is that DNA is central. But maybe DNA came along a lot later as a regulatory mechanism.

In other computational experiments we're looking at very simple animals and modeling their neural development. We're looking at polyclad flatworms, which have a very primitive, but very adaptable brain with a couple of thousand neurons. If you take a polyclad flatworm and cut out its brain, it doesn't carry out all of its usual behaviors but it can still survive. If you then get a brain from another one and you put it into this brainless flatworm, after a few days it can carry out all of its behaviors pretty well. If you take a brain from another one and you turn it about 180 degrees and put it in backwards, the flatworm will walk backwards a little bit for the first few days, but after a few days it will be back to normal with this brain helping it out. Or you can take a brain and flip it over 180 degrees, and it adapts, and regrows. How is that regrowth and self-organization happening in this fairly simple system? All of these different projects are looking at how this self-organization happens with computational experiments in a very artificial life-like way.

The third piece is trying to see if we can generate some mathematical principles out of these robots and these computational experiments. That, of course, is what we're really after. But at the same time, my research methodology is not to go after a question like that directly, because you sit and twiddle your thumbs and speculate for years and years. I try to build some real systems and then try and generalize from them.