# Memory in HPCT

**URL:** <http://discourse.iapct.org/t/memory-in-hpct/6902>\
**Category:** CSG1992\
**Created:** [December 7, 1992, 3:57pm UTC](http://discourse.iapct.org/t/memory-in-hpct/6902 "1992-12-07T15:57:31Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Allan\_F\_Randall](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/a/dbc845/32.png) [@Allan\_F\_Randall](http://discourse.iapct.org/u/Allan_F_Randall)\
**Post date:** [December 7, 1992, 3:57pm UTC](http://discourse.iapct.org/t/memory-in-hpct/6902/1 "1992-12-07T15:57:31Z")

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Hi all,  
&nbsp;&nbsp;Although there have been delays, I am happy to say that I am now working  
full-time on Martin Taylor's control project. I will be working in  
conjunction with Chris Love and Jeff Hunter.  
&nbsp;&nbsp;Anyway, my first order of business is to get more properly grounded in  
control theory, so I have just finished giving "Behaviour: The Control Of  
Perception" a thorough reading (BTW, my formal background is in computing  
and AI).  
&nbsp;&nbsp;I am intrigued by the model of memory presented in Chapter 15. Bill, is  
this still your working model, or has it changed? (I know its been a while  
since you wrote the book). Do you still see the basic function of memory  
as providing reference signals? Do you see the imagination loop as  
operating through memory as it does in the book? Or have the intervening  
years changed your conception of the problem? My conception of the diagram  
on page 221 is that the memory unit would take references from the  
higher level ECSs and remember how the world is supposed to act, so the  
memory is basically a little toy world inside the ECS (a toy world, that  
is, for all the ECSs above it that feed it references). This is a neat  
model, I think, especially with the switches that give the four  
different modes of behaviour. But I also realize there are probably many  
other spcific ways of implementing memory that do not conflict with the  
basic HPCT scheme, so I am wondering how you feel about this model now,  
twenty years later.  
&nbsp;&nbsp;I had previously thought of imagination mode as one ECS telling upper  
levels that they are controlling, even though they aren't. However,  
talking with Martin recently, he pointed out the need to imagine that a  
reference has NOT been satisfied, as well as imagining that it had, I  
realized this model can do this as well. If the memory box is acting as  
a little toy world, then it can respond in imagination mode that  
"no, this won't work." -- the higher level ECS will experience prolonged  
error in imagination.  
&nbsp;&nbsp;I also found it interesting that you used the RNA model of memory. Have  
you dropped this idea since the RNA theory has fallen out of favour?

Allan Randall, randall@dciem.dciem.dnd.ca  
NTT Systems, Inc.  
Toronto, ON