Braitenberg Vehicles

Braitenberg vehicles are simple automatons, conceived in thought experiments proposed by the cyberneticist Valentino Braitenberg. They illustrate the abilities of reactive agents, thus representing the simplest form of Behavior based AI or embodied cognition, i.e. intelligent behavior that emerges purely from sensorimotor interaction between the agent and its environment, without any need for an internal memory, representation of the environment, or inference.

Mechanism

A Braitenberg vehicle is an automaton that can autonomously move around. It has primitive light sensors and wheels (each driven by its own motor) that function as actuators or effectors. A sensor is directly connected to an effector, so that a sensed signal immediately produces a movement of the wheel. Depending on how sensors and wheels are connected, the vehicle exhibits different, goal-oriented behaviors. This means that it appears to strive to achieve certain situations and to avoid others, changing course when the situation changes.

The following examples are some of Braitenberg's simplest vehicles.

1) A first agent has one light-detecting sensor that directly stimulates its single wheel, implementing the following rules:
* more light produces faster movement
* less light produces slower movement
* darkness produces standstill

This behavior can be interpreted as a creature that is afraid of the light and that moves fast to get away from it. Its goal is to find a dark spot to hide.

2) A slightly more complex agent has two light detectors (left and right) each stimulating a wheel on the same side of the body. It obeys the following rule:
* more light right → right wheel turns faster → turns towards the left, away from the lightThis is more efficient as a behavior to escape from the light source, since the creature can move in different directions, and tends to orient towards the direction from which least light comes.

3) In another variation, the connections are negative or inhibitory: more light → slower movement. In this case, the agents move away from the dark and towards the light.

In a complex environment with several sources of light and shadow, Braitenberg vehicles will exhibit a complex and dynamic behavior. They will describe a zigzagging trajectory with accelerations and slowdowns, moving as fast away as possible from any strong light sources while apparently exploring the surroundings, until they find a deep pocket of shadow where they can “rest”. This behavior is undoubtedly goal-directed, flexible and adaptive. We might even see it as intelligent, the way we attribute some minimal intelligence to a cockroach. Yet, the functioning of the agent is purely mechanical, without any information processing or other apparently cognitive processes.

References

*Braitenberg, V. (1984). Vehicles: Experiments in synthetic psychology. Cambridge, MA: MIT Press.
*Lambrinos, D., Scheier, Ch. (1995). [ftp://ftp.ifi.unizh.ch/pub/institute/ailab/techreports/95.10.ps.gz Extended braitenberg architectures] . Technical Report AI Lab no. 95.10, Computer Science Department, University of Zurich.

External links

* [http://www.kyb.mpg.de/~braitenb Valentino Braitenberg's homepage]
* [http://people.cs.uchicago.edu/~wiseman/vehicles/ A software Braitenberg vehicle simulator]
* [http://www.ai.rug.nl/~gert/applets/braitenbergJRE/ Another Braitenberg vehicle simulator] , lets you play around with different settings, vehicles and sources