[ACT-R-users] Modeling ideas

[Wolfgang Schoppek]

Hello Troy,
 
> First, I need to model the recognition of two types of visual
> stimuli, where one stimuli is more recognizable than the other
> stimuli.

That depends on the reason why the two types of stimuli are
differently
recognizable. If it is perceptual conspicuity (such as number of
discriminating basic features), you either have to use PM or estimate
time and probability of success for the basic perceptual processes.
If it is differences in complexity (such as number of parts),
differences 
can be modeled in the cognitive layer. Categorizing more complex
stimuli
may take more steps (production cycles).

>  I don't think I am going to be using P/M, so I don't
> necessarily have to worry about how P/M would handle such a task, if
> it can handle such a task.  I don't think I will be using an
> external simulation that PM can access, but I might if it is the
> only way to represent the discrimination of visual stimuli.  I have
> been thinking of using partial matching to represent this
> discrimination problem, but any other ideas would be appreciated.

For more concrete hints, could you describe your task in a little more
detail?
 
> Also, I have some data that shows a workload effect on performance
> after a certain critical workload level has been reached, which then
> causes performance to level off after the critical point has been
> reached.  So, I have 3 conditions (easy, medium and hard) and
> performance is good during the easy condition, but it changes to be
> poor performance for both the medium and hard conditions.  So the
> workload reaches a critical point during the medium condition, which
> negatively effects performance, and essentially stays that way for
> the hard condition as well.  Any ideas on how to model this -
> "change in performance after a certain critical point has been
> reached" - would be appreciated.

That looks like a threshold effect, which can easily be modeled using
the dynamics of source spread and retrieval theshold. More workload 
usually means there are more chunks sources of activation and
therefore,
each of them spreads less activation into the network. So with growing
workload the potency for being a retrieval cue goes down for the 
activation sources. Together with the retrieval threshold this can 
produce the "critical point" effect.

-- WS
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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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