unconstrained retrievals

[Wolfgang Schoppek]

(Servan-Schreiber & Anderson, 1990) in ACT-R 5.0. In that model, I use
something like unstructured working memory that contains elements of
the stimulus in arbitrary slots. An example is:

 **Newgoal25    3.006
    isa WM-FREE
    s1 A-0
    s2 B-0
    s3 nil
    s4 D-0
    s5 1-0
    s6 2-0
    s7 3-0
    s8 Pattern15  (represents the former contents of s3 and s8)
    count 7
    ret nil
    task 'learning

In declarative memory, there are chunks ("patterns") that may
represent all possible subsets of the set of elements of Newgoal25.
For example, a pattern like:

 Pattern2    0.251
    isa PATTERN
    pa nil
    pb B-0
    pc nil
    pd D-0
    p1 nil
    p2 nil
    p3 3-0
    p4 nil

would match, but there are lots of other patterns that might match as
well. Because of the large number of possible combinations, I don't
constrain the retrieval of patterns with productions like:

(p retrieve-pattern
  =goal>
    ...
 ==>
 +retrieval>
   isa pattern
   pb B-0
   p3 3-0
...)

Instead, I use unconstrained retrieval that simply returns the most
active chunk:

(p retrieve-pattern
  =goal>
  ...
==>
  +retrieval>
    isa pattern
  =goal>
  ...
)

Now the problem with this kind of retrieval is that it often returns
chunks that are already elements of the goal (because of the strong
self-activation of chunks), which is of course undesired in the
present context. Does anybody know a good solution to that problem or
is there even a "standard" solution?

-- Wolfgang
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Dr. Wolfgang Schoppek          Universitaet Bayreuth
 Tel.: +49 921 554140
 http://www.uni-bayreuth.de/departments/psychologie/wolfgang.html
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