Now to get onto some psychology at last: some more detailed reading on production systems and modelling.
Note when reading her productions that you work from the bottom up, not the top down!
Pages 154--168 continue from the topic of GPS as a model to production systems. Page 164 lists what Newell and Simon take to be the architectural features of the mind.
You may find the OU book heavy going if you work straight through from page 83. Unfortunately, it starts by discussing models of cryptarithmetic-solving, and they are not particularly simple.
Possibly this order will help:
See what Young was trying to do with his model. Try dry-running the simple rules in figure 25 page 115.
The notation for rules is different from before. The condition
and action are separated by arrows. In the condition, there are
tests of the form
goal=add first block.
These test the top goal on the goal stack, which is a part
of STM. In terms of the next paragraph, these look at the top
message on the spike, never anything lower down. There are also
tests of the form ``task just started'' or ``holding block in
hand''. These test perceptions of the outside world.
In the action, there are things like
push(goal = add first block). This put the symbols
add first block onto the goal
stack. Think of the goal stack as a spike, initially empty, onto
which you can push bits of paper.
push(goal = add first block)
pushes a piece of paper with
goal = add first block onto the
spike. As mentioned above, the tests
goal = X always look at the
message at the top: anything lower down is invisible until it's
There are also actions of the form
pop goal stack. These take
the top (and only the top) piece of paper off the spike,
uncovering what's underneath.
This notion of a stack is described on p 105 of the OU book. Using goals stored on a stack to control rules is a bit like what Bagger did. The difference is that Bagger only ever noted one goal (the current goal). Here, we can store a whole stack of them.
Question: is this psychologically realistic? How deep can the stack be?
Read the comparison between this model and Piaget's explanation.
Skim the computational details, except in section 2.4. Pick out the issues relevant to psychological modelling. Note the comment about ``cheats'' on p 92. Ignore comments about SOLO (it's a bit like Prolog, if you know Prolog). For STRIPS, read GPS: in the points he's making, there's little difference between them.
Read in detail. Note the concepts of production memory, working memory (i.e. STM), how rules are activated, conflict resolution.
Note the three different strategies. In general, you can make many different sets of production rules to model any one behaviour. How do you know which best fits the mind....?
Now go back and dry-run the different sets of rules. See how well they model a child as it develops.
The issue of modelling.