Braitenberg begins with his simplest vehicle, one in which a single sensor is attached to a single motor. His innovation with this vehicle: the propulsion of the motor is directly proportional to the signal being detected by the sensor; so, the stronger the sensed signal, the faster the motor. "Here we have introduced a bit of Aristotelian physics. Aristotle, like everybody else between this ancient Greek philosopher and the less ancient Italian physicist Galileo, thought that the speed of a moving body is proportionate to the force that drives it."
In a frictionless world, the behavior of this vehicle should be straightforward. For example, imagine that the vehicle moves through a pool of water, and that the sensor detects temperature. The vehicle will always move in a straight line, slowing down in the cold, speeding up in the warm.
Complications in the behavior of the vehicle arise by making the environment more complex. For instance, add the effect of friction. Now, the vehicle can come to a full stop when the temperature that it senses drives the motor so slowly that the force of friction cannot be overcome. Friction will also cause random deviations in trajectory, producing something like Brownian motion + thrust.
"Imagine, now, what you would think if you saw such a vehicle swimming around in a pond. It is restless, you would say, and does not like warm water. But it is quite stupid, since it is not able to turn back to the nice cold sport it overshot in its restless ness. Anyway, you would say, it is ALIVE, since you have never seen a particle of dead matter move around quite like that."
The preceding paragraph provides one of Braitenberg's basic themes: the inferred properties of the system (based on the basis of behavioral observations) are more complicated from the known structure of the artifact from the designer's perspective.
Some questions to keep in mind now that this theme has been presented: How does this reflect upon cognitive psychology, or indeed on any school of psychology in general? Is the methodology of psychology necessarily going to provide theories that are more complex than required?
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