[ACT-R-users] Chunks by reference

[Dan Bothell]

--On Thursday, May 11, 2006 3:22 PM -0300 Lucas Vitti Rodrigues 
<lucas.vitti at gmail.com> wrote:
>
> My doubt is: Is there a way to retrieve chunks by reference? Or is it
> incompatible with the cognitive model?
>

If you are using ACT-R 6.0 then the answer is yes, but with two
small caveats.  The production you have is almost valid as it stands:

>
> (p start-comparison
>             =goal>
>                         Isa compare-chunks
>                         Chunk1 [=chunk]
> ==>
>             +retrieval>
>                         [chunk1]
> )
>

If you just drop the square brackets and reference the variable
on the RHS:

(p start-comparison
    =goal>
       Isa compare-chunks
       Chunk1 =chunk
 ==>
    +retrieval> =chunk
)

it will request a retrieval of a chunk that "looks like" (has the
same chunk-type and slot-value pairs as) the one bound to =chunk.

The first caveat would be that if for some reason there were duplicate
chunks in declarative memory that looked like the one requested (which
can only happen if you explicitly put them there) it could result in
any of the duplicates being retrieved (which ever one had the highest
activation).  The other issue is that if you have partial matching
enabled, as with any other retrieval, you could have an incorrect
retrieval due to similarities and noise.

Dan