As described on the Behavior-based_robotics Wikipedia page:
Behaviour Based Systems (BBS) came out of the Rodney Brooks and the MIT Robotics Laboratory and represents a research area distinct from AI that attempts to model the robot's environment (with computer-based ontologies, 3D modeling, etc.) or accumulate great amounts of data, or build some kind of robot world view. BBS consider that small creatures like insects don't have a complex model of the world as they hardly have a brain at all, simply some hard-wired, reactive behaviours. Likewise, a combination of behaviours wired into a robot creates an emergent form of intelligence, to some degree in a ratio corresponding to the complexity of the sensors (or the robot's "view" of the sensed environment).
See also: Behaviour Trees