how can ACT-R models age?

[Carol L. Raye]

episodic memory, so I will throw in 2 cents. 

In response to what Erik wrote, I have to say, I don't think
"the fecundity of learning mechanisms leads to pervasive
acquisition of episodic memory" is a description of older
adults. Episodic memory is event memory and requires that
one bind together in memory the features that make up the
event. We have evidence that older adults have a binding
deficit in encoding episodic memories. For example, in a
working memory task they are less able than young adults to
bind the features of an event together into an episodic
memory, even when they recognize single features at the same
level as young adults. Our fMRI data for this task is also
consistent with an encoding deficit--less anterior
hippocampal activation in older adults in the feature
binding condition. Older adults also show deficits in many
source memory tasks (e.g., which of 2 speakers said what)and
again we have evidence of poorer encoding. In addition to
changes in underlying brain mechanisms, we have some
evidence that older adults may attend to different
information, e.g., attend less to perceptual features and
more to emotional than young adults--and they show some
benefit from instructions to focus on perceptual
information. In short, I agree with Lynne Reder that
acquiring new information is a significant problem with
aging. With respect to Lynn Hasher and colleagues' proposal
that older adults have a general failure in inhibitory
mechanisms, I found it appealing but when I last read the
work, I did not find the evidence as compelling as I would
have liked. Below are two recent references from our lab on
binding and aging.

Mitchell, K. J., Johnson, M. K., Raye, C. L., Mather, M., &
D'Esposito, M. (2000).  Aging and reflective processes of
working memory:  Binding and test load deficits.  Psychology
and Aging, 15, 527-541.
Mitchell, K.J., Johnson, M.K., Raye, C.L., & D'Esposito, M. 
(2000). fMRI evidence of age-related hippocampal dysfunction
in feature binding in working memory.  Cognitive Brain
Research, 10, 197-206.

Erik M. Altmann wrote:
> 
> At 9:04 PM -0500 1/4/01, Lynne wrote:
> 
> >My impression of aging effects is that the *biggest* liability of
> >aging is in acquiring new information not retrieving old
> >information--this occurs  with  poor encoding of simple facts, but
> >is most pronounced in learning new skills and concepts.  It seems
> >that older individuals are most handicapped in domains where their
> >prior knowledge is of least value, e.g., learning new technologies
> >or video games.   It is not obvious to me how Erik's filling up the
> >brain with too many chunks would predict that general
> >pattern/problem with
> >aging.  My hunch (and again, since it has not been simulated it is only a
> >hunch) is that W would do a better job of explaining that aspect of
> >the demise of intellect with age.
> 
> I expect there are many liabilities to cognitive aging, and I can't
> claim to know which is the "biggest", but there is evidence that
> cognitive aging involves a decreased ability to inhibit irrelevant
> information -- that is, an increased susceptibility to interference.
> See May, Hasher and Kane (1999), for some recent examples, and Kane
> and Hasher (1995) for a review.
> 
> >Erik's other remark was that his proposal was a natural consequence
> >of aging, while W is a free parameter.  Well, it would at least be
> >constrained to go down with age, not up.  Moreover, it is a single parameter,
> >while my reading of Erik's proposal involved twiddling several parameters,
> >but perhaps I'm mistaken (low W and lots of decayed chunks due to my
> >advanced age, or at least, that's my excuse).
> 
> This comment raises a question about how to interpret model
> parameters theoretically.  I'm not sure that number of parameters by
> itself is the best criterion for evaluating the success of a model.
> In the limit, a model with a single parameter set to "do the task"
> would not be particularly interesting.  My concern about W, and also
> about partial matching, relates specifically to this point.  As I see
> W and partial matching often used, they redescribe the data rather
> than explaining the data in terms of underlying or more complex
> processes.
> 
> I have little invested in my aging proposal (as yet!) and don't care
> to be dogmatic about it, but it does serve as a counterexample in
> that it involves multiple parameters.  Of course it involves multiple
> parameters, not to mention multiple assumptions -- it's a process
> account, and any complex process will involve many degrees of
> freedom.  This is not by itself a drawback.  The more interesting
> question is how well those degrees of freedom are constrained, both
> externally by other data and theory and internally by mutual
> constraint among mechanisms, and what questions they raise to drive
> further research.
> 
> In searching for constraints on this model, I would start by fixing
> the decay rate at d =0.5, which has worked well now in many models.
> The big question would probably be the rate at which chunks are added
> to memory.  There's evidence from many sources, including the ACT-R
> Argus models being developed at GMU, a slough of models in Soar,
> Logan's instance theory, etc., that elements are added to memory at a
> relatively constant rate -- the "fecundity" of learning mechanisms
> leads to pervasive acquisition of episodic memory.  So, pick a
> constant rate.  But then, what's the effect of consolidation, say
> during sleep?  Is this what causes the decay rate to "slow down" as
> John et al recently documented?  More generally, what's the
> physiology of decay?  And what's the interaction with cues spreading
> source activation to really old chunks, reviving those old memories
> and feeding back into their retrieval history?  These questions come
> up because the account is a process model with lots of parameters and
> assumptions.  Stopping with W, like explaining semantic gradients
> with partial matching, cuts off discussion of how the history and
> context of the system might produce or moderate the effect of
> interest.
> 
> Cheers,
> 
> Erik.
> 
> May, Hasher, & Kane (1999).  The role of interference in memory span.
> Memory & Cognition, 27, 759-767.
> 
> Kane & Hasher (1995).  Interference.  In Maddox (ed.), Encyclopedia
> of aging (pp 514-516).
> --
> 
> ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
> Erik M. Altmann
> Department of Psychology
> Michigan State University
> East Lansing, MI  48824
> 517-353-4406 (voice)
> 517-353-1652 (fax)
> ema at msu.edu
> http://www.msu.edu/~ema
> ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

-- 
Carol L. Raye
Sr. Research Scientist
Dept. of Psychology
Yale University
P.O. Box 208205
New Haven, CT 06520

Phone:  203.432.6762
Email: carol.raye at yale.edu