Competing "retrieval" rule vs compiled "habit" rule?

[Niels Taatgen]

attachment to an email you send off. I almost thought I caught one of 
those in Erik's email, but later on realized he only promised that the 
paper he mentioned could be found on his homepage.
I think many people already made good points about the topic, so I would 
like to elaborate on the issue of working-memory capacity, as this is 
mentioned by a couple of people. My intuition is that there can be two 
reasons for forgetting to buy bread. One reason is that the chunk 
encoding this task has lost its activation and cannot be retrieved 
anymore. Although this might be a legitimate reason, I do not think it 
is the case that occurs most often, as these types of errands tend to 
pop up later in your memory, even though the context may do nothing to 
prompt it. This means that working-memory capacity in the usual ACT-R 
sense (retrieval failures tied to W) cannot be the problem.
Now, what's happening in this car driving/chatting/thinking about the 
bread scenario is that we have a heavy case of multi-tasking. So you 
might consider it a small miracle that you think about the bread after 
all! Frank (Lee) and I have been trying to model multi-tasking, and it 
turns out declarative memory is the main bottle-neck. No, that's not 
really true, all buffers can be bottle-necks, but declarative memory is 
one we can do something about, as production compilation removes 
declarative retrievals. If declarative memory is "doing nothing", as is 
the case when you are driving a car, because you are waiting for 
perceptual things to happen and motor things to conclude, there is 
plenty of time to engage declarative memory in other things 
(daydreaming, having a conversation, thinking about the bread). You need 
some way to flag the busy-state of declarative memory, so Frank and I do 
this in the goal.
In our very small demo-model, there is a main task A, and a secondary 
task B. The main thing for the model to do is task A, but when it has 
some slack time it can work on B as well. It turned out that task B only 
gets a chance to be processed in parallel with A once A has been 
proceduralized, producing some slack time for declarative memory (by the 
way: Frank and I but together a paper for the cognitive science 
conference on this http://www.ai.rug.nl/~niels/CogSci2002Final.pdf). A 
similar situation is going on the the bread-on-the-way scenario: if you 
are too much engaged in conversation, there is no opportunity to steal 
slack time at the right moment. But if the conversation gets boring, and 
your minds drifts off... well you might just remember the bread!

Niels

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Niels Taatgen - University of Groningen, Artificial Intelligence
web: http://www.ai.rug.nl/~niels     email: niels at ai.rug.nl
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