Schema thy from an act-r perspective: Comments?

[Wayne Gray]

Taken from a work-in-progress. Reflections upon an act-r account of schema
theory. First two paragraphs introduce schemas and what they are used for.
"AOs" are submarine approach officers. Third paragraph provides the ACT-R
explanation of schemas. I hope the first two paragraphs are coherent out of
context. Question for the group -- have I missed anything? Are schemas
really simply an "intervening variable" or is there more? Are they a
hypothetical construct? (If you have no idea what the distinction is and if
it is not obvious from the context, check out:

MacCorquodale, K. and P. E. Meehl (1948). "On a distinction between
hypothetical constructs and intervening variables." Psychological Review
55: 95-107.

A truely important paper.)

Wayne

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We alluded above to the AO's ability to see patterns among attributes of
the solution. This ability to recognize a well-formed solution by
identifying the interrelationships and constraints present in the data,
implies the existence of certain types of data-structures in the AO's
long-term memory. In the psychological literature, such data-structures are
often referred to as schemas (Brewer & Nakamura, 1984; VanLehn, 1989). They
function to organize and represent large amounts of related information.

We postulate that AOs have such data-structures and use them in two ways.
First, at any given time, the schema provides a summary of the current
state of the situation assessment. This summary guides the AO in deciding
what to do next; i.e., what piece of information (attribute) is currently
the most important to obtain. Second, the schema organizes the data in such
a way as to make a good solution apparent. Whether the schema triggers a
recognition-like process ("ah-hah, I have it!") or merely supports a more
deliberate assessment of the current information are alternatives that will
not be addressed here. The important point is that (a) schemas provide a
pre-existing organizational structure into which the data may be placed as
it is received, and (b) the schema is what is interrogated (either by
pattern recognition type processes or more deliberate processes) to
determine if a good solution has been found.

At the theoretical level, we view schema as an intervening variable not as
a hypothetical construct (MacCorquodale & Meehl, 1948). In our view, a
schema is simply a specialized set of declarative memory elements (DMEs)
and their associated procedural memory elements (productions). The DMEs
that compose "a schema" differ from other DMEs only in that they constitute
specialized types of DMEs (i.e. task specific) with preexisting
(pre-scenario) attributes and values, and strong preexisting associative
connections to other task-specific DMEs. Likewise, the schema productions
differ from other productions only in that they are specialized to operate
upon the schema DMEs during performance of a very specialized task. To say
that our AOs have schemas for situation assessment, is a simple claim that
they possess a set of interrelated DMEs and productions that are
specialized for the situation assessment task.

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Wayne D. Gray  HUMAN FACTORS & APPLIED COGNITIVE PROGRAM

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