A HYBRID MODEL OF REASONING BY ANALOGY

3) In AMBR a mechanism similar to ACME (Holyoak & Thagard, 1989b) is used which is a form
of relaxation search in a connectionist network. In the case of AMBR where objects have
corresponding descriptions (in contrast to ACME where objects are semantically empty) this
mechanism makes it possible to establish the correspondences between objects and relations in
parallel.
There is a number of differences between the constraint networks in AMBR and in ACME. First,
in contrast to ACME, in AMBR this is not a separate network but is an temporary built extension
of the LTM of the reasoner. Consequently, the state of the reasoner's mind (the presently active
elements of LTM and the relations between them) will influence the relaxation search. Second, in
contrast to ACME, prior to relaxing the network, in the phase of its construction, it is possible to
establish some correspondences (between objects or relations) when they are highly relevant and
semantically similar. This will restrict the space of possible mappings described by the network.
This makes it possible to model both cases: a) internal domain or close domain analogies where
usually object similarity plays a major role and b) abstract analogies between far domains where
usually higher-order relations dominate the mapping.
Cognitive architecture
GENERAL DISCUSSION
Continuousness vs. Discreteness Dualism: A Hybrid Approach
A hybrid cognitive architecture is proposed which combines the advantages of a symbolic approach
(used for complex structured representation of situations, problems, plans, concepts, etc. as well
as for the benefits of a marker passing mechanism in specialized search tasks) with the strength of
connectionism in associative retrieval and soft constraint satisfaction.
These different approaches are highly integrated. It is not the case that each part of the system is
organized according to one of these approaches (communicating with the other parts). On the
contrary, it is rather the case that different processes (symbolic and connectionist) work on the
same structures which are considered as frames by the symbolic processes while the connectionist
mechanisms consider them simply as nodes and links. This is possible because of the specific,
rather distributed frame organization. Although there is a single frame representing a given object
or concept, a lot of frames have to be traversed in order to extract all information about it, i.e. there
is a whole network of frames describing an object. This is due to the fact that there is no local
information in the frames but only references (pointers) to other frames. The same links are used
both for spreading activation and for marker passing, but the two processes are not independent:
the possibility for, and the speed of marker passing strongly depend on the activation of the nodes.
In this way the connectionist aspect of the architecture continuously "restructures" the knowledge
base of the reasoner represented by the symbolic aspect thus controlling the set of possible
inferences at any moment. It makes some nodes more accessible and others inaccessible, thereby
assigning priorities, restricting the search, etc. This makes the knowledge base dynamic and
context-dependent.
There is actually a dual representation of the current situation:
a) an implicit distributed representation - the distribution of activity in the whole network (LTM)
according to the associative relevance of each memory element, and
b) an explicit local representation - a structured symbolic representation of the situation including
its most important elements and the relations between them.
In this way symbolism and connectionism are considered as dual aspects of human cognition