[ACT-R-users] different base level activations

[Roman Belavkin]

Hello Sarah,

> Is there a way to give different base level activations to
> different chunks or different chunk types?
> In my model, one type of chunk should be harder to retrieve
> than the other chunks, so I would like to give such a chunk
> a lower base level activation at the moment of its creation
> (it does not exist from the beginning).

I am not sure if it will help you, but you can set the levels of individual
chunk.  The way you do it depends on whether the model learns the
base-levels (the :bll mechanism is on or not).  If it does, then you can
change the chunks' levels by defining their creation times and numbers of
past references.  For example, in a model of a mouse I used, there was a
chunk representing the current state of a mouse (self state).  Because I
believed that there should not be a long time to retrieve such a chunk, I
set its base level to a high value by defining the long in the past creation
time (could be approx the age of a mouse in seconds) and high value of
references:

(set-base-levels (self 1000000 -1000000))

negative is the creation time.

Interstingly, this helped the model a lot to achieve a better match with the
data.

Now, regarding the base level of a specific chunk type, I am not aware of a
command in ACT-R that can do it, but certainly it is possible write a
function like this yourself.  Can you tell use why would you want to do it?

Cheers,
Roman Belavkin
http://gold.mdx.ac.uk/~rvb/