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4.2 Attributes of Reactive Paradigm
fixed-action pattern type of response, where the behavior persists for a short
period of time without the direct presence of the stimulus. The main point is
that behaviors are controlled by what is happening in the world, duplicating
the spirit of innate releasing mechanisms, rather than by the program stor-
ing and remembering what the robot did last. The examples in the chapter
emphasize this point.
The five characteristics of almost all architectures that follow the Reactive
Paradigm are:

1. Robots are situated agents operating in an ecological niche. As seen earlier in
SITUATED AGENT Part I, situated agent means that the robot is an integral part of the world. A
robot has its own goals and intentions. When a robot acts, it changes the
world, and receives immediate feedback about the world through sens-
ing. What the robot senses affects its goals and how it attempts to meet
them, generating a new cycle of actions. Notice that situatedness is de-
fined by Neisser’s Action-Perception Cycle. Likewise, the goals of a robot,
the world it operates in, and how it can perceive the world form the eco-
logical niche of the robot. To emphasize this, many robotic researchers say
ECOLOGICAL ROBOTICS they are working on ecological robotics.
2. Behaviors serve as the basic building blocks for robotic actions, and the overall
behavior of the robot is emergent. Behaviors are independent, computational
entities and operate concurrently. The overall behavior is emergent: there
is no explicit “controller” module which determines what will be done, or
functions which call other functions. There may be a coordinated control
program in the schema of a behavior, but there is no external controller
of all behaviors for a task. As with animals, the “intelligence” of the ro-
bot is in the eye of the beholder, rather than in a specific section of code.
Since the overall behavior of a reactive robot emerges from the way its
individual behaviors interact, the major differences between reactive ar-
chitectures is usually the specific mechanism for interaction. Recall from
Chapter 3 that these mechanisms include combination, suppression, and
cancellation.
3. Only local, behavior-specific sensing is permitted. The use of explicit abstract
representational knowledge in perceptual processing, even though it is
behavior-specific, is avoided. Any sensing which does require represen-
EGO-CENTRIC tation is expressed in ego-centric (robot-centric) coordinates. For example,
consider obstacle avoidance. An ego-centric representation means that it
does not matter that an obstacle is in the world at coordinates (x,y,z), only