# Let's get on with it

**URL:** <http://discourse.iapct.org/t/lets-get-on-with-it/6326>\
**Category:** CSG1995\
**Created:** [October 14, 1995, 7:04pm UTC](http://discourse.iapct.org/t/lets-get-on-with-it/6326 "1995-10-14T19:04:37Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Bruce\_Abbott](http://discourse.iapct.org/letter_avatar_proxy/v4/letter/b/ba8739/32.png) [@Bruce\_Abbott](http://discourse.iapct.org/u/Bruce_Abbott)\
**Post date:** [October 14, 1995, 7:04pm UTC](http://discourse.iapct.org/t/lets-get-on-with-it/6326/1 "1995-10-14T19:04:37Z")

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[From Bruce Abbott (951014.1400 EST)]

> Bill Powers (951014.0720 MDT) --

> Systems that behave the same way, from the standpoint of an external  
> observer, are not necessarily organized the same way inside.

I agree.

> Structures  
> that appear anatomically the same do not necessarily accomplish their  
> functions in the same way.

True as far as it goes. Yet, is there any reason to believe that the  
control system by which I move my arm and the one my dog Muffie uses to move  
her front leg might have something in common, not only in their structural  
organization but also in their functional organization? This is not to say  
that the two structures are identical--after all, there are important  
structural and functional differences as well. No, they do not  
\_necessarily\_ accomplish their functions in the same way, but observation  
and testing can reveal whether they do or not. That wonderful little  
diagram in B:CP showing the gross anatomy of the lowest-level  
muscle-length/force control system was first worked out in other animals,  
yet turns out to apply rather well to the homologous human system, despite  
there being some differences.

Control systems are organized to create

> certain outcomes, but the fact that the same outcomes keep occurring  
> does not mean that the same actions were used each time to create them.

True, but I'll bet the same control system, having the same anatomical  
locus, initiated those actions in accordance with its error signal, and that  
is the point being debated here, not whether the same control system always  
produces the same actions.

> If a bird builds a nest and a mouse builds a nest, there is no reason to  
> conclude that birds and mice share a common nest-building ancestor.

True enough: there must be other evidence before one can draw such  
conclusions. One must distinguish those cases whereby similar natural  
requirements have produced independent, analogous solutions, which may  
depend on very different biological machinery, from cases in which the  
solutions emerged early and persisted (although perhaps with modification)  
over evolutionary history.

> Nests have several functions, and an adaptive control system  
> organization will find a way to accomplish those functions quite  
> independently of how any other system might have accomplished the same  
> functions. If it happens that two organisms use the same method to  
> accomplish the same function, the reason may be simply that there is no  
> other easily-found method that will accomplish that function. One can't  
> conclude that there is some specific structure inside the organisms that  
> makes them both use the same method and hence get the same result.

Yes, and that is precisely why one needs to observe both function AND  
structure before one can reach any secure conclusions on the matter. The  
bee's vision system and the rat's are clearly examples of parallel  
evolution; the rat's visual system and ours, on the other hand, show clear  
signs of having been derived over the course of evolution from the same  
protostructure. Human and rat evolution have resulted in modification and  
elaboration of this basic system along different lines (for example, the  
human eye contains photoreceptors that make color vision possible, whereas  
the rat eye does not), and one can expect important differences between  
these two species to be found in the neural circuitry involved in analyzing  
the visual input. Yet the basic organization of the rat's eye and ours is  
the same, both species have optic nerves which partially cross at the optic  
chiasm, both optic tracts then run to the lateral geniculate nucleus of the  
thalamus and synapse with neurons located there, and those neurons in both  
species send their axons to the occipital lobes of the cerebral cortex,  
where they terminate on cortical cells in such a way that the spatial  
organization of the primary visual area lays out point-for-point like a map  
of the retinal surface of the eye. Is it logical to believe that this  
parallel organization is an accident of parallel evolution, and that the  
structural similarities have nothing to tell us about probable functions  
these structures serve? I think not. Yes, one must be careful not to  
assume too much--over the course of evolution old structures do sometimes  
take on new functions through modification of their detailed connections,  
but you seem to be suggesting that one can learn nothing at all from the  
study of other animals that will help us to unravel the puzzle of human  
brain function. Am I overstating your case?

Getting back to nesting, birds and mice may have independently evolved (not  
learned) control structures that lead, under appropriate conditions, to the  
building of nests. In both cases the nest is a solution to a problem posed  
by the animal's environment in conjunction with the animal's individual  
needs. The mere fact that both build nests is not sufficient to conclude  
that the same brain structures are involved. Yet all birds of a given  
species build their nests in the same way, using the same stereotypical  
movements, although there is considerable flexibility in program to allow  
for such variables as what nesting material is available. The same may be  
said for rats. Having discovered that particular areas of the bird's (or  
rat's) brain organize this system in its particular way, it would be no  
surprise to find that the homologous structures of related species are  
similarly organized to serve a similar function. Knowledge of this system  
in birds may not apply to rats and vice versa, but the question of whether  
it does is an empirical one that can be settled by appropriate research.

> The problems I see in your arguments and explanations is that behind  
> them there seem to be large numbers of assumptions that are contrary to  
> these principles. Moreover, these contrary assumptions are widely shared  
> in your profession, to the point where they are taken for granted. The  
> difficulty I'm having is in raising doubts about these assumptions  
> without appearing to claim that they are false. By trying to cast doubt,  
> I am not trying to claim that I know your statements are wrong, but  
> trying to show that there is a level of investigation that is called for  
> to find out whether the assumptions are justifiable. If stimulating a  
> rat's amygdala results in a rat's showing visible behaviors which, if  
> they occurred in a human being, would be called fear, this is not an  
> indication that the rat is experiencing fear or that the effect of the  
> stimulation on the rat is the same as it is for the human being. It's  
> not an indication to the contrary, either. It's an open question, which  
> can be resolved only by further investigation. The rat's amygdala has  
> been evolving just as long as the human's, and by now could be  
> performing functions with no parallels in the human, and accomplishing  
> similar functions by quite different means. COULD be.

You may be surprised, but I absolutely agree (except for the first sentence,  
see below). If we differ on this issue, it would appear to be in the degree  
to which we believe that the data support these assumptions, or perhaps in  
our beliefs as to the degree to which researchers have been sensitive to  
these questions and have sought out evidence with which to addrress them.  
My experience has led me to conclude that in ceratin areas of research there  
is reliable empirical evidence that supports the assumptions on which my  
arguments have been based. But I agree that your concerns about  
interpretation are certainly cogent and ought to be uppermost in the minds  
of everyone doing this kind of research. It is all too easy to be mislead  
by surface similarities. In my opinion, however, in the areas of research  
about which we've been debating there have been serious efforts made to  
address these issues through empirical work.

> I guess we'll have to put aside some arguments if we're to make progress  
> in developing PTC applications to behavior. I can see the logic in your  
> answers to my questions and comments, but can't seem to get across the  
> framework from which my questions arise.

I'm wondering if the problem isn't highlighted in something you said earlier:

> Nests have several functions, and an adaptive control system  
> organization will find a way to accomplish those functions quite  
> independently of how any other system might have accomplished the same  
> functions.

Perhaps our difference lies in the degree to which we believe that adaptive  
reorganization can restructure the functions of the brain. By "adaptive" I  
assume you mean systems capable of being reorganized until some organization  
is found that establishes control over some perceptual variable, as opposed  
to parallel evolution in which different structures may evolve to serve  
similar functions. To some unknown extent the functional organizations of  
your brain and mine may differ because our experiences have led to our  
developing different systems for controlling particular variables and even  
to different variables being brought under control. We can go further: in  
young children damage to brain structures in one hemisphere (e.g., Broca's  
area in the left frontal lobe) often leads to changes in the functinal  
wiring of the other hemisphere so that the function reemerges there. The  
brain's wiring is surprisingly plastic, at least up to a point. But this  
fact should not lead one to conclude that the brain is infinitely plastic,  
that any function can appear anywhere as a result of rewiring guided by  
experience (reorganization).

Following destruction of Broca's area, the language functions served by  
Broca's area will reappear in the young child, not anywhere, but in the  
homologous structure of the right hemisphere, and in the adult it will not  
appear at all. Furthermore, if our two brains were examined and compared  
after our deaths, neuroanatomists would find the same recognizable  
structures in both: medulla, pons, cerebellum, hypothalamus, and so on, and  
the same nulclei in the same relative positions within each of those  
structures. Yes, there would be some differences in the sizes of certain  
structures and in the number of nerve fibers comprising the same neural  
tracts, and at some points there would be detailed differences in neural  
interconnections wrought by our differing experiences. In few of those  
structures would there be any significant difference in what had been the  
structure's function. Perhaps you have learned to play the Saxiphone and I  
have not. Clearly this difference in abilities would indicate that you  
possess control systems, formed through practice, that I lack. Yet the  
basic structures within which those systems developed would be essentially  
the same in you and me, and serving similar functions.

> The problems I see in your arguments and explanations is that behind  
> them there seem to be large numbers of assumptions that are contrary to  
> these principles.

Large numbers of assumptions? Now there's a vague referent! Contrary to  
these principles? Which principles? Contrary in what way, to which  
specific assumptions? Perhaps a short list, giving the assumption, the  
principle to which it is contrary, and a brief explanation why you think the  
two are contrary might help. I believe I have shown that the assumptions I  
make are justified by the data and not at all contrary to any principles of  
PCT. What am I missing? I think the suggested listing could help  
enormously to clarify your position for me.

Regards,

Bruce