The name is absent

behaviour will be executed. The motivations will compete until only one will be able to execute
its corresponding behaviour.

Satiation. When a creature controlled by BeCA executes a consummatory behaviour to
satisfy one of its needs, this need will decrease. Once the need is satisfied, it will not motivate
the execution of the behaviour any longer.

Changes in responsiveness. When an internal need is satiated, the entity controlled by
BeCA will have a change in its responsiveness, selecting a different behaviour.

Persistence in the execution of a consummatory behaviour. The feedback from the
Drive/Perception Congruents level to the perceptual persistence internal behaviour allows the
consummatory behaviour previously executed to have a higher possibility to be executed, as
long as the external and internal signals corresponding to the behaviour are still strong. For
example, if an agent controlled by BeCA is hungry and thirsty, and he finds food and water,
there will be no switching from eating to drinking and back with every time step. The agent will
execute a consummatory behaviour until the corresponding internal need is adequately
satisfied.

Interruption in the execution of a consummatory behaviour. If a creature controlled by
BeCA is executing a consummatory behaviour, this can be interrupted in the presence of a
sudden need or a reflex or more imperative reactive behaviour. For example, if the creature is
drinking, and he perceives a predator nearby, he might interrupt the satiation of his thirst in
order to run away.

Varying attention. This property is defined by ethologists as the less importance that an
animal gives to danger (e.g. a predator) when the animal has an extreme motivation (e.g.
starvation) (McFarland, 1981). This property emerges from the competition at a motivational
level. If an agent controlled by BeCA is very hungry, even if he is perceiving a predator, he may
try to satisfy his hunger, because of the intensity of the signal representing the internal need.

3.10. About the Behavioural Columns Architecture

“All things are what one thinks of them”

—Metrodorus of Chius

The BeCA evolutionary bottom-up style of engineering, and many of its properties, were
facilitated by the blackboard architecture, which provides a great flexibility and capacity of
integration and of being intrinsically opportunistic.

There are many reasons to think that the BPS presented and discussed in previous
sections is something more than a simple action selection mechanism. BeCA integrates in a
single model an extensive repertoire of properties and principles desired in adaptive
autonomous agents. Although different subsets of these properties can be found characterizing
other ASMs and BPSs reported in the literature (Tinbergen, 1950; Tinbergen, 1951; Lorenz,
1950; Lorenz, 1981; Baerends, 1976; Brooks, 1986; Brooks, 1989; Rosenblatt and Payton, 1989;
Maes, 1990; Beer, 1990; Beer, Chiel and Sterling, 1990; Hallam, Halperin and Hallam, 1994;
Negrete and Martmez, 1996; Goetz and Walters, 1997), none of them present all of them as a

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