Distributed (D) vs. Centralized (C) Approaches
- Who's in charge?
- D: Nobody. There is the illusion of someone being in charge
because the behavior seems purposeful, and it seems to be possible
to write a centralized program to make it happen.
- C: A central controller, someone who sends commands to
various modules (components) of the system, coordinates the
activities of the modules, and selects among candidate
processes at each point in time.
- What do the basic processes look like?
- D: They involve very simple interactions among primitive elements,
for example, the spread of activation or the alignment of phase
- C: They involve symbol manipulation: the creation of symbol
structures by putting symbols together, matching of symbol structures,
searching through lists of symbol structures.
- What order do things happen in?
- D: Many processes happen in parallel (simultaneously).
- C: Processes happen sequentially (one at a time).
It is necessary to select among candidates.
- How does the creature interact with the world?
- D: Through perception and action components which are similar
to the more internal parts of the system.
In some models, the environment and the creature itself constitute
one large dynamical system.
- C: Through perception and action interfaces which are very
different from the internal parts of the system.
- What form does knowledge take in the creature?
- D: It is distributed, usually in the form of patterns of connectivity
among the primitive parts. It may be impossible to simply read it
- C: It is explicit and symbolic.
- How does the knowledge get into the creature?
- D: It is learned as the creature is exposed to inputs
from the world and responds them to them, or it evolves as
generations of creatures are forced to survive in the world.
- C: It is usually programmed in by someone with a theory
of how knowledge is organized. Some parts of it may be learned.
- How is time handled?
- D: The problem of temporal short-term memory is often addressed,
though the continuous interaction of components of the system
with each other and the world may not be.
In the most conservative approaches, input patterns are
fed to the creature in the form of a sequence of discrete
events. In the most radical approaches, the creatures
exists in the world in continuous time.
- C: Time may be mapped onto space; that is, the system
has simultaneous access to all of pattern of some length (a
sentence, a piece of music, a sequence of images).
Inputs may also be presented to the system sequentially,
but the temporal short-term memory problem is usually side-stepped
because the inputs are preprocessed.
Take me back to the Rhythm and Cognition
Last updated: 5 December 1995
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