[ACT-R-users] computational basis of act-r

[Hongbin Wang]

Shadows of the mind

When the mind works, it leaves shadows that people can observe. Suppose a
student S solved the equation "2x+5=9" and it turned out the response time
was 2s. Both researchers JA and RO tried to understand what had happened in
this 2s period. JA looked S' verbal protocol (e.g., "I move 5 to the right,
and do the substraction. So I get 4, ...") and developed an Act-R model to
simulate the underlying knowledge structure of S' behavior. RO looked S'
fMRI recording and found the medium temporal lobe is particularly involved
in the process. Based on well-documented principles of how the brain works,
RO developed a neural networks model to simulate S' behavior. While both
models fit the data well, the question is, which one is right?
Apparently, both models are valuable. While the Act-R model is
psychologically plausible the neural networks model may be more biologically
realistic. Both models captured some characteristics of the mind's work,
though at different levels (i.e., symbolic and subsymbolic). Importantly,
these different levels are all "real", and no one is more real than another.
A cognitive architecture that permits psychologically plausible symbolic
modeling and makes nontrivial predictions will not be outdated. 
How to find the possible links among these different levels of
shadows/models is the hard (and right) question. Act-R is already moving
forward in this direction. Act-R5's symbolic components have been mapped to
possible brain structures based on recent neuroscience results. Though
rudimentary, it may not be too far away in time for people to start link
Act-R to brain processes such as oscillation. The link would not be
straightforward and linear. But as long as they all are shadows of the mind,
they should be linked.


Hongbin Wang
School of Health Information Sciences
University of Texas Health Science Center at Houston

-----Original Message-----
From: Chris Chatham [mailto:chatham at m-laboratories.net]
Sent: Tuesday, January 14, 2003 6:55 AM
To: act-r-users at act-r.psy.cmu.edu
Subject: [ACT-R-users] computational basis of act-r

A couple of days ago, I talked to a researcher at Penn's Institute for
Research in Cognitive Science who believes ACT-R will be outdated in the
next couple of years.

He believed that the fundamental method of computation in the brain is
"oscillation" and that because ACT-R has no computational similarity to the
neurological structure of the brain, it will always be a poor modeling
architecture.

I asked whether ACT-R might be expanded at the subsymbolic level to include
this type of modeling.  Any thoughts here from the group, or in regards to
the IRCS researcher's opinion?

-Chris.


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