The Future of ACT-R in the
Post-John Era
Appendix: The Future of ACT-R
Upon re-reading the Appendix in
Chapter 1 on the history of ACT-R, I
was struck by two observations. I have
had a very poor history of predicting
where ACT next. Therefore, I am wise
to make this appendix short to
minimize the embarrassments of my
mispredictions. The second
observation is that the evolution of the
ACT theory has really been driven by
external inputs (the right branches in
Figure 1.11). Some of these were from
outside our laboratory and some were
essentially parallel activities within my
laboratory at CMU.
HAM
(Anderson & Bower, 1973)
0.Simulate Complex Cognition
1. Symbolic Declarative
PSG
(Newell, 1973)
2. Symbolic Procedural
ACTE (Anderson, 1976)
3. Subsymbolic Declarative
4. Subsymbolic Procedural
Interactive Activation Model
McClelland& Rumelhart (1981)
5. Neurally Inspired Subsymbolic
Caveat Emptor:
So Anything I Say
is Probably False
Anderson (2007). P. 247
ACT* (Anderson, 1983)
6. Goal Directed Processing
7. Production Compilation
Rational Analysis
Anderson (Anderson, 1990)
8. Bayesian Adaptation
ACT-R 2.0
(Anderson, 1993)
9. Public Simulation System
ACT-RN
(Lebiere & Anderson, 1993)
10. Limited Pattern Matching
ACT-R 4.0
(Anderson & Lebiere, 1998)
11. End-to-End Simulations
EPIC
(Meyer & Kieras, 1997)
12. Perceptual-Motor Modules
ACT-R 6.0 (current)
13. Brain Mapping
14. Instructable Production System
I hold these truths to be self-evident:
1. ACT-R 6.0 is perfect.
2. LISP was a mistake.
3. It’s time for John to go.
ACT-R 6.0 is Perfect
It is marvelously maintained.
Its module structure facillitates the “let a
thousand flowers bloom” philosophy.
But where is the theory?
While there sort of is a core theory, there are
multiple variants of the ACT-R theory and ACT-R
6.0 formalizes how they relate.
Despite the push in Cognitive Science towards
toothbrush theories, we do have a community
using the core ACT-R 6.0, even if they are using
it to build their own toothbrushes.
One of the reasons ACT-R 6.0 is perfect is that
it allows ACT-R, the theory, to evolve to
incorporate new theoretical developments.
It is also gratifying that there is so much effort
to produce versions of ACT-R that have greater
usability (at least for designated purposes).
The Dilemma of the No-Magic Doctrine
Newell’s 20 questions -- unhappiness with theories that addressed little
pieces with no idea if they would fit into a working system.
It really took decades and the work of many people to get ACT to where it is
today -- perhaps not perfect but ACT-R 6.0 is now….
1. Experimentally grounded (stimulus to response)
2. Capable of a detailed and precise accounting of data
3. Learnable through experience (including task instructions)
4. Capable of dealing with complex phenomena
5. Controlled by principled parameters (and all can be turned on)
However, it is a rare ACT-R model that does all of these things.
Having built a few I have to report that there is no reward. To publish them
you have to focus on an aspect and ignore the rest.
No one wants to read about all of the details.
No one will check that you actually did everything you said.
However, they may will be suspicious that you are hiding something.
The benefit-cost ratio is much higher if you build a small, describable model
that addresses just a piece and leaves the rest to imagination.
LISP was a Mistake
It was the success to the extent that it brought smart people (e.g. Christian
Lebiere) to the world of ACT-R.
It also allows rapid prototyping of theory (maybe not uniquely).
However, it makes ACT-R more inaccessible to others and this is getting
worse.
It allows people to believe ACT-R is just an old-style symbolic AI theory.
It exacerbates the no-magic dilemna:
1. LISP helps justify ignoring what ACT-R has achieved in addressing
the no-magic issue.
2. The power of LISP makes may make it easier to fake solutions.
What to do about LISP?
Trying to get an agreement on an alternative is probably a bigger
mistake. It would tear up our pleasant community with language wars.
The LISP implementation will remain the reference even if more work
is done in other languages.
However, we should be welcoming of various alternative
implementations of ACT-R.
The response to various tools and implementations to make modeling
in ACT-R easier is more complex:
1. They are clearly good things that should be welcomed when
they achieve what they claim -- making it easier to pursue research
and explore the ACT-R theory.
2. However, we need to be vigilant that we loose sight of the nomagic doctrine and slip into fantasy world where we are not really
modeling human cognition.
It is time for John to Go!
This is the last time I hacked ACT-R.
I have now come to use it as a tool.
Partly this is because of the modular
structure of ACT-R 6.0.
However, this is also because my
interest have moved to understanding
events at a higher temporal grain size
than the architecture.
I think this meeting is ample
testimony to the fact that things are
progressing just fine without my
intimate involvement.
And I think the community would
prosper more if it did not depend on my
social and organizational skills (e.g.
Niels & Hedderik’s Spring School).
So we (Dan) will continue to support
6.0 but ACT-R is very much a
community effort.
And What About the 2011 18th
Annual ACT-R Workshop?
It is in part a matter of what is decided about the next ICCM.
If there is a summer ICCM in 2011 (rather than a Spring ICCM in
2012), the default would be to try to attach a one-day workshop to it.
If there is no summer ICCM, the default would be have a CMU-based
workshop on the heels of the ACT-R summer school.
There has been the feeling we need a community opportunity to
reflect on the direction of ACT-R much in the spirit of the 2001 postgraduate summer school.
Over the past 2 years there has been some attempt to create this in
face of the 2 summer ICCMs but for many reasons none of the plans
took hold.
One reason was that the ball was in my court.
Maybe it is time to have someone else (a committee?) take charge of
such community organizing, if not for 2011 then for beyond.