Embodied Robotics and Emergent Behaviours

Rodney Brooks heads the AI Lab at MIT, a pioneering centre in embodied robot research. According to Brooks, by 2020 or so we will share the planet with robots that have emotions, desires, love and pride. One of their early successes was 'Genghis', an insect-like creature with six legs and compound eyes. Genghis’' eyes and legs are the inputs and outputs for simple behaviours such as 'chase', 'stand-up', 'walk over obstacles'. But when combined together in one body, cued by stimuli from the environment, the result is a robot that behaves like many insect predators we encounter in nature. Brooks describes it as having a wasp-like personality.Importantly, this was achieved with no central cognition. When independent observers witness Genghis, they can't help but describe Genghis' actions in terms of novel emergent behaviours for which Genghis has no programming or physical correlates.A reductive approach would deny this claim; if there are no correlates then the behaviours must be illusory. Let’s consider a much-simplified example of a robot that exhibits an emergent behaviour. Imagine a robot with four wheels and a light sensor on the front that supplies power to the rear wheels in proportion to the light level it receives. (There is no digital computation on this particular robot.) It will go forward while there is light in the room falling on its sensor and stop when it has driven far from the light. This robot can hardly be said to be intelligent. However, if we add a second light-sensor, so there are now two where the headlights would be, and if we wire the left sensor to the right wheel, and the right sensor to the left wheel, what will happen? Just like a moth to flame, the robot will drive to the light from wherever it is in the room. If it incorrectly veers to the left, the right light sensor, seeing more light, will send more power to the left wheel and put it back on course. This self-correction occurs until it finds its goal. If the light is then moved, it will follow. The brighter the light, the more vigorously it will seek it. How should we describe the behaviour of such a robot? I think we must call it ‘light-seeking’. Importantly the robot responds in time, with what seems to be a beginning point, a period of trial and error, and a goal temporarily achieved, before potentially restarting its search if the light is moved. But there are entirely no programming or physical correlates to this temporally based behaviour. A hardcore reductive approach would insist on describing this robot in terms of a dual set of light-sensors, motors and drive wheels. The light-seeking behaviour would be taken to be illusory. I think this is obviously false. On the other hand, if the emergent behaviour is real, would it be correct to say this robot and Genghis have intentions?They certainly behave as if they do...

While Brooks is more than sympathetic to the reality of emergent behaviours, he believes that designing human-like robots will turn out to be relatively easy because "we are machines", "... nothing more than a highly ordered collection of biomolecules". I believe he comes to this conclusion by extrapolating his key insight that led to the success with Genghis’ and which continues with the Cog and Kismet projects. The insight was: leave out cognition. Prior to Brooks' work, the vast majority of AI researchers were trying to develop computer programmes that followed human-like cognitive processes, and robots that used these kinds of programmes to control parts of the robot by maintaining a high-fidelity software model of the robot’s state and the world around it. This turned out to be significantly harder than expected. Meanwhile, Brooks decided to see how far he could get by building robots equipped with just basic responses to their environment, and explicitly leaving out any large cognition feature. The answer was: surprisingly far.

Email link | Printer-friendly | Feedback | Contributed by: Adrian Wyard