Who Needs Emotions? The Brain Meets the Robot

architectural basis of affect 223
Corresponding to the different kinds of processing mechanism and
semantic resource available in the central subsystems, we can also distinguish
layers of abstraction in the perceptual and action subsystems. For instance,
a deliberative layer requires perceptual mechanisms that can discretize, or
“chunk,” the environment into categories between which associations can
be learned that play a role in planning and predicting future events. It is not
always appreciated that without such discretization, multistep planning
would require consideration of branching continua, which appears to be
totally infeasible. Another sort of correspondence concerns the ability of organisms
to perceive others as information-users. Doing this requires perceptual
processes to use concepts for other agents that are similar to those the
meta-management system uses for self-categorization. 5 Examples might be
seeing another as happy, sad, attentive, puzzled, undecided, angry, looking
to the left, etc. Similarly, layers of abstraction in an action system could evolve
to meet the varying needs of central layers.
Superimposing two threefold distinctions gives a grid of nine possible
sorts of component for the architecture, providing a crude, high-level classification
of submechanisms that may be present or absent. Architectures
can vary according to which of these “boxes” are occupied, how they are
occupied, and what sorts of connection there are between the occupants of
the boxes. Further distinctions can be made as follows:
whether the components are capable of learning or fixed in their
behavior
whether new components and new linkages develop over time
which forms of representation and semantic content are used in
the various boxes
In Figure 8.2 we indicate the possibility of a reactive component that receives
inputs from all the other components and sends outputs to all of them.
This could be a design for an “alarm” system that detects situations where rapid
global redirection of processing is required, one of the ways of thinking about
the so-called “limbic system” (discussed in Chapter 3 by Kelley and in Chapter
4 by Fellous and LeDoux), although there can be many more specialized alarm
systems in a complex architecture, such as a protective blinking reflex.
This schema provides a generic framework relative to which particular
architectures can be defined by specifying types of components, types of links,
types of formalisms, and types of mechanisms used in the various components.
This subsumes a very wide variety of types of architectures, and within
each type a wide variety of architectures of that type. See also Sloman and
Logan, 2000 and Sloman, 2000b.
Many architectures that have been investigated in recent years are purely
reactive (Nilsson, 1994). Some purely reactive architectures have layers of