[ACT-R-users] Towers of Hanoi in ACT-R 6?

[Leon Urbas]

Hi Rob,

As far as I understand the tower of hanoi examples heavily rely on
manipulation of a perfect goal stack via push and pop. This psychologically
unplausible assumption was given up with ACT-R 6, unfortunately without an
equivalent architectural replacement. 

Since development of a central executive seems to be still at an early
stage, we had to develop a quick hack to force our ACT-R 6 models to
reliably "jump" back to a previous goal: as soon as we want to switch to a
subgoal we label the current goal with an unique id and remember this id in
a slot of the new goal. This was necessary because relying on
activation-decay of the previous goal gave us unacceptable high error rates
in goal/sub-goal control in our dynamic environments. 

(P branch-to-subgoal
	...
 ==>
 	!bind! =id (get-time)
    	=goal>
 		id		=id
   	+goal>
		isa		...
		state		start
    		last-goal-id 	=id
)

This allows us to retrieve exactly this goal later on when sub-goal
processing has come to an end (iff retrievable)

(P retrieve-previous-goal
	=goal>
		isa		...
		state		finished
		last-goal-id	=last-goal-id
	?retrieval>
		- state		busy
==>
	+retrieval>
		...
		id		=last-goal-id
)
(P copy-retrieved-goal-to-goal-buffer
	...
   	=retrieval>
		...
        	slot1		=value1
		...
        	slotn		=valuen
==>
	+goal>
		...
        	slot1		=value1
		...
        	slotn		=valuen
)

We are not really happy with this solution, because this hack

a) costs execution time (but goal-switching indeed comes with a cost)

b) efficiently supresses chunking (because of the unique id)

c) is unsuitable for partial matching (id has no link to the goal-state
characteristics)

d) is as inplausible as the former goal-stack


Iff the distinct goal-states as defined by the values of the goal-slots is
an enumberable set, we could define a simple hash-function to label them -
this would solve at least issues (b) and (c). 

Still, the problem of goal-switching would be solved on a modell level and
not on an architectural level. But perhaps a high level language approach
might be the key for the observed variability in users goal management
abilities.

We are very much interested to learn from other's approaches.

Best Regards,
Leon
--
Technische Universitaet Berlin - Center of Human-Machine-Systems
Technische Universitaet Dresden - Institute of Automation
Dr.-Ing. Leon Urbas
Tel.: +49 (30) 314-72007        
      +49 (351) 463-39614
Fax.: +49 (30) 314-72581
http://www.zmms.tu-berlin.de/modys/
http://www.vernetztes-fahren.de/
http://www.prometei.de/

 




> -----Ursprüngliche Nachricht-----
> Von: act-r-users-bounces at act-r.psy.cmu.edu 
> [mailto:act-r-users-bounces at act-r.psy.cmu.edu] Im Auftrag von 
> Robert St. Amant
> Gesendet: Montag, 8. Mai 2006 18:12
> An: act-r-users at andrew.cmu.edu
> Betreff: [ACT-R-users] Towers of Hanoi in ACT-R 6?
> 
> Hi, all,
> 
> In our work on translations between modeling languages, it 
> would be very helpful to have a model for the Towers of Hanoi 
> problem that was in the most recent version of ACT-R.  The 
> three that are most readily available in the repository all 
> seem to be for ACT-R 4; we'd like to have one that doesn't 
> involve explicit manipulation of the goal stack.
> 
> Thanks,
> Rob St. Amant
> 
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