Function: embodied, embedded and autonomous
Xabier Barandiaran
xabier@barandiaran.net
http://barandiaran.net
18-04-02
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18-04-02 |
Essay for the ``History and Philosophy of
Adaptive Systems'' course by Proff. Margaret Boden at the
Evolutionary and Adaptive Systems MSc at COGS, University of Sussex,
Brighton, UK. |
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According to a hermeneutic gadamerian attitude there is one single
way
to be objective and that is to make our prejudices, intentions and
interests as explicit as possible in a cognitive quest
(as every coursework and essay ought to be), and test them against
the
alterity of the text:
be it the Bible, the episodes of life, the chapters of political
history
or the book of nature to whose pages
we (as philosophers of adaptive systems), in this course, belong.
We shall, thus,
specify that it is not our concern in this essay to work upon
a general theory of function, autonomy and adaption (which will
go beyond the reasonable aims of an inmature coursework) but
to detect and work (as a artisan would do) upon some problematic
(and other hopeful) conceptual issues regarding the theoretica
framework of the scientific-cognitive practice on complex adaptive
systems. Our ultimate goal is to work towards a framework for the
cognitive, so, although our discussion will be more grounded in
biological phenomena, this will be so within the framework of a
bottom-up
continuity thesis by which we understand that cognition, as a late
phenomena in the evolutionary history of organisms, must be
understood
and grounded in biological organization and history, in its
biological
conditions of posibility, biological trascendentals (à la
`naturalized' Kant). We tend to categorize complex realities in
hierarchical levels (cells, organisms, communities, societies,
etc.), and
the idea that higher levels of complexity (and adaptation) can be
explained form lower level 'dynamics' and components articulates an
ambitious scientific program.
But the theoretical and pragmatic demands of our scientific
practice
requires more than a program, more than an intuitive idea. Methods,
frameworks
in which experiments and theory are to be articulated and
connections
between different levels of analysis are required.
In this essay we explore the concept of function, specially its
evolutionary version (whose significance is central in contemporary
biology --and philosophy of the mind) and try to link it with the
concept of autonomy, exploring how a normative notion of function
can be sustained by present causal mechanisms.
We try to explore how a next step in the hierarchy of
complex systems could be achieved by redefining this terms in the
cognitive
domain.
Functionalism stands for one of the most relevant theoretical
frameworks
in the history of biological and cognitive sciences. The relevance
of
the functionalist framework can be understood from a double
requirement
it fulfills when facing the understanding of adaptive systems:
- As the grounds for semantic, intentional (mental)
and
teleological explanations whose presence in human
understanding
(be it philosophical, historical, or folk psychological) and
self
(conscious) comprehension and control, is essential. Some
phenomena
are seen as empirically untestable because they require a
backwards
causation (future outcome explains present trait or behaviour
1):
teleological
and intentional phenomena belong to this class and a functional
framework is required to ground the scientific explanations of
such
phenomena.
- As a higher order of description from purely
physicalist
or behavioral explanations . When facing certain phenomenal
spaces (specially those over the fields of physics and
chemistry in a
hierarchy of sciences)
in which mechanistic explanations (in terms of the physical
components and mechanisms involved in the phenomenon) do not
reduce the complexity of the phenomena under study to
epistemologically
and pragmatically efficient grounds, functionalist explanations
are
seen as a necessary conceptual tool.
The functionalist framework, by decomposing adaptive systems into
functional
components, stating its causal and formal relations, and/or by
specifying
its selective advantages, can be said to be the common (or at least
classical) ground to analyze and understand biological and
cognitive
systems. But what do we mean by functionalism? How is the concept
of
function articulated with this purpose?
Ned Block [1] identifies three senses of
functionalism:
decompositional, computational and metaphysical.
- Decompositional functionalism relies on the
methodological
strategy of decomposing a system into components and analysing
its
functional role.
- Computational functionalism (Putnam and Fodor),
relying on
the computer metaphor, proposes that functional states are
equivalent
to those achievable by digital computers or Turing machines.
- Metaphysical functionalism claims that mental
states are
functional states, independently of its physical realization.
The main claim of functionalism is the claim that the essence
of a function
(and a functionally decomposable system) is not its physical
realization
but the causal structures (relations) involved among
components.
Computational functionalism provides the epistemological grounding
of
a formalizable theory of the mind in terms of logical relations
between
states, inputs and outputs of a system. Since different physical
devices
can (in principle) instantiate the same formal (computational)
relations,
functionalism is often related to the so called
multiple realizability hypothesis.
The behaviour of an ant can be taken as an example of functional
explanation: if COLLECTING-FOOD, AVOID[low-quantity-sources],
GO[to-big-energy-sources]. This is a functional (computational)
explanation:
the ant is in state COLLECTING-FOOD, and has to execute to outputs:
AVOID and GO. But that is `just' a functional interpretation both
`AVOID[low-quantity-sources]' and
`GO[to-big-enery-sources]' are human categories never present
as such in any mechanism giving rise ant behaviour.
What we interpret as GO[to-big-energy-sources] is a complex
process that emerges
from local interactions with other ants through trofolaxis
(chemical `communication') and path following behaviour
2 as well as from internal neural dynamics. This independency
between
the physical and the functional, although considered as the biggest
strength of functional explanations (specially regarding the
ontological
status of mental events) introduces several dificulties when
trying to cope with the complexity of the underlying physical
mechanisms
from wich functions are predicated. But before going into the
analysis
of such problems we shall point to an alternative conceptualization
of
function that trys to solve the following question (among others):
How can we assure the interpretative adequacy (if our
interpretation
is correct or just a methaporical description far from what `really
is goin on' in the system under study) of a functional
explanation3?
On the other side of the functional stand a more evolutionarily
oriented concept of functionality has been developed by several
authors (Wright, Millikan, Sober, Maynard Smith,...) We will focus
on Millikan's account of `proper' function, exposed in
[15], as one of the most
representative conceptualization of this notion of evolutionary
function.
Evolutionary or Selected functions are defined in terms of history
rather
than ``the item's present properties or dispositions'' (p.288). The
formal
definition goes as follows (a simplified version of Millikan's
definition is
given here):
The item A has the proper function F iff:
- A originated as the reproduction of A' and
A
causally-historically exists because A' performed function F
in the
past; or
- A originated as a product of some prior device
A'
that: a) had F as a proper function and b) that causes F to be
performed by means of producing an item like A.
(this will be a derived proper function).
In short: F is a proper function of A if the performance
of F helped
the proliferation of the ancestors of A. An example can be
illustrative
at this point: the function (F) of the shell (A) of a turtle is to
protect the turtle because the shell has been reproduced over the
generations precisely because of its protective function.
Millikan pretends to give
a theoretical definition of function in the sense of proper purpose
and
not a universal definition of anything that can be said to perform
a
function (the rock functions as a paperweight). Nontheless she
claims that,
as a matter of fact, having (or performing) a function corresponds,
in
the mayority of cases, with having a proper function. For Millikan
the
approaches that try ground the concept of function in terms of
structure
or disposition fail to account for failure in purpose (nothing in
the
present structure can account for normative, the disposition is as
it
is). Historical analysis, on the other hand, does account for those
cases.
Evolutionary functionalism provides the temptative conclusion of a
happy coupling scenario between a functionalist theory of
representations
and an adaptationist evolutionary theory: the epistemological
normativity
of representations can be grounded in the fact that organisms must
adapt
to an objective environment. Thus adaptation and representation get
married
in the grounds of evolutionary function. Intentional explanations
can be
grounded in selection (the content of a representation is fixed by
selection) and ants do AVOID[low-energy-sources] because it
is
evolutinarily advantageous.
But the 'happy' evolutionary functionalism is not out of
theoretical
and pragmatic problems. Millikan recognizes that the historical
dependency of its definition of proper function runs out the
possibility
of (logically possible) accidental doubles to have a function
4 But she argues that such `logically possible' cases are fallacious
constructs that do not, as a matter of fact, happen in reality.
Millikan follows that other definitions of function according to
which
accidental copies do have functions, are just descriptions of
markers that do help us recognize functions but do not address
the constitutive nature of function and purposiveness which is
rightly addressed by her definition of proper function, from
which the rest of the markers parasite. As a matter of fact,
Millikan concludes, functions (and any non historical definition
of them) depend on their being proper functions.
But the artificiality of accidental exact copies, twinearthian
logical possibilities, and other analytic angloamerican scholastic
affections do not run out the whole problematicity space of
Millikan's definition
5.
The theoretical reason is that if selection (and consequent higher
differential reproduction) is considered as a modeling factor of
complex
adaptive systems whose mechanisms (although selected by evolution)
operate by means of their physical instantiations, selection cannot
be
considered as ontologically present in the system under study,
selection
is not a present cause of any behaviour or dynamic of the system,
as
pointed out by Maturana [9]
6 .
Thus proper functions turn to be ontologically separated from the
system
in which they are performed. This turns to be
specially problematic when considering the following sort of
questions:
- The question of the origin of a function.
A function must perform as a
function to be selected. Millikans account falls into a
petitio principii because the function of a trait
recursivelly refers to its historical function.
- The question of functional innovation (new meanings,
learning,
new adaptive strategies, etc.). How do new functions arise
remains unresolved in her proposal. Although Millikan
does not pretend to address this issue in her account of
`proper' functions, it is of primary importance specially if
we take into account that cognitive and adaptive systems
often have to find innovative solutions to problems they never
encoutered before.
- The question of function determination when there is no
access to history. How do we determine the function of a trait,
or behaviour, when the history of the system it belongs to
is unaccesible or nonexistent?
These questions can be summarized in the following one:
- How can we ground functionality to be ontologically tided
to
the system it belongs to and still have a `proper' hermeneutic
horizon
in which evaluate different functional accounts?
Although Millikan's approach can be an interesting way to
normativize
the concept of function it leaves (as we have seen)some fundamental
problems unresolved. In particular those related to organization
(how
function relates to its physical realization and other components
in
a system), origins
and the nature itself of the concept of function. Her definition is
circular in that sense (proper functions require previous
functionality
of ancestors, and so on ad infinitum).
The problems pointed out on Millikan's account of functionalism are
not
the only problems that a functional explanation must face. As
Emmeche
points out [6] any functional account must face
three
major problems:
- Formalization may not catch all the causally effective
mechanisms
- ``The construction that implements the formal structure is
still in
need of our interpretation in order to give any meaning.''
Meaning is a
projection of an observer if it cannot be linked with
materiality
(semantics are not intrinsic to syntax á la Searle).
- Formally, functionally, equivalent systems can be
absolutely non
equivalent in real life where time and energy can be essential.
This problems point to the importance of the physical
(energetical, spatial
and temporal --dynamical) embodiment of functions. The
embodiment and
environmental embededness of adaptive (biological and cognitive)
systems
give rise to specific problems of functionalism that has been
pointed out
by Andy Clark [2,3] under the label of
interactive emergence. Interactive emergence points to two
major
difficulties:
- Dissolution of functional accounts in highly
interactive loops.
This is the agent-environment side of
interactive emergence by wich behavioural functions are the
outcome of
complex interactive loops between agent and environment where
the causal
mechanisms are difficult to specify by classical computational
functionalism
since functional units/behaviours cannot be isolated from the
agent-environment metasystem. In this sense Luc Steels
[13]
defines behaviour as an emerging from the direct interaction
and control of different components and mechanisms with the
environment
and other agents. This way emergent functions cannot be
understood as
formal relations between components of an organism or adaptive
mechanisms to certain environmental conditions. A dynamical
definition
of function is proposed instead with more emphasys on indirect
control
and the tendency of interactive asymptotic stability (the
agent-environment
system tends to a dynamic equilibrium)
- Dissolution of functional units in distributed causal
networks.
Probably one of the major chalenges to functionalism comes from
the connectionist approach, its main conceptual weapon being
the focus
on the importance of a distributed causal mechanisms where no
specific
component can be said to perform a specific function. The major
problem
of a distributed causal network is not that there are no
directly specifiable
physical components that perform independient functions
(because functionalism
does not require a physical decompositionality) but the fact
that this
distributed nature of the mechanisms constraints and modifies
the behaviour
or nature of a trait. Some things cannot be explained by
(evolutionary) functional
accounts because they are caused by complex underlying dynamics
which are
not subjected to functional analysis. Langton [] points to the nonlinear
nature of biological organism: their behaviour is the effect of
the
interactions between components (unlike linear systems where
the global
behaviour is the summ of the behaviour of the components
analyzed in
isolation) and an explanation of the system must study it as a
hole,
requiring a synthetic efford, rather than an analytic one.
In this section we shall finally consider how the concept of
autonomy can help solving some of the problems mentioned above
(specially those concerning the mechanistic nature of a function
and its normativity) and how autonomous robotics and computer
simulations become necesary tools for this synthetic and holitic
efford.
The concept of autonomy as a central notion for the study of
biological, cognitive and adaptive systems in general has been
largelly ignored by clasical funcitonalist. First introduced
by Maturana and Varela in [10] under the concept of
autopoiesis, autonomy becomes the key notion from which
biological systems are understood from a systemic perspective.
We shall point out how the concept of autonomy can contribute
to solve the problems mentioned above by considering some of
the main characteristics of autonomy.
The basis of all autonomy is the
active (internal and external) role of the system to contribute
to its self-maintenance: the production of components and
the
active change of boundary conditions of the system to
maintain the essential variables (energy, temperature, etc.)
homeostatically. In fact autonomous systems wouldn't exist
in nature without this central characteristic. Ruiz-Mirazo
and Moreno [12] have developed the notion of
basic autonomy by specifying the termodynamic and
energetic requirements of a system to be autonomous in
this sense. The physical
realization of a function is analyzed by the authors
dynamically integrating energetic and termodynamic constraints
into the explanation. This way the function of a component can
be explained not as its adaptation to an external feature
of the environment but as its contribution to the
self-maintenance
of the system [] (structure and function are thus
integrated in the physical realization of the autonomy of
a system 7).
The normativity of a function can be,
thus, refered to its physical realization and not to its
past history (the heart of your magic twin copy has a
function becaus it is activelly contributing to the
maintenance of the system). It should be noted that this
reference to the self maintenance is compatible with the
millikanian account but still solves some of its problematic
holes and it is not constrained to its metabolic side.
Metabolic reactions
are sometimes too slow to maintain an internal stability
under rapidly changing conditions, that is the role of
the nervous system connecting sensory-motor surfaces
to deal with environmental changes rapidly and without
involving change in the purelly metabolic proceses. Thus
the nervous system, metabolically decoupled but embeeded in
the organism has to know how to evaluate the results of
its body control. Affections and internal sensors become
then major features to autonomously build an cognitive
internal normativity [4].
A second level of functionality (cognitive functionality) can thus
be described where nervous mechanisms anticipate the effect
of environmental interactions for the self-maintenance of
the system without having to produce the interaction itself
(and subsequently compensate for the produced desequilibrium of
essential variables). This way what grounds
semantics is not an absolute epistemological
stand which requires absolute observers but the
intrinsic evaluative mechanisms of a cognitive agent.
The concept of function must be grounded in autonomy (from a
bottom-up basic autonomy approach) if we want to develop
appropriate tools to understand and conceptualize adaptive
systems without falling into an hermeneutic relativism (everything
can be interpreted as functional) but avoiding recursion to
history as a causally effective mechanism. Autonomy becomes, thus,
the hermeneutic axis of a bottom up explanation of adaptation and
cognition.
In this task computer simulations are to be found as
necesary tools not only in the modeling of concrete phenomena but
in the development of a proper conceptual frameworks, specially
by the interactive-emergent nature of biological and congnitive
functions. The synthetic enterprise but at work by the artificial
life community is the first steep for a more sincere cognitive
relation with our complex world.
- 1
- Block, N. (1980)``Introduction: what is functionalism?''
in Block, N. (Ed.) Readings in the philosophy of psychology. Cambridge,
MA, Harvard University Press. pp. 171-184.
- 2
- Clark, A. (1996) ``Happy couplings: Emergence and
explanatory interlock'' Chapter 9.
of Boden, M. The Philosophy of Artificial Life, Oxford
University Press, 1996.
- 3
- Clark, A. Being There. Putting Brain, Body,
and World Together Again. MIT Press, 1997.
- 4
- Christensen, W.D. and Hooker
C.A., (in press) ``Self-directed agents''. Macintosh, J. (Ed.)
Contemporary Naturalist Theories of Evolutiona and intentionality.
Canadian Journal of Philosphy, 31, Special Supplementary Volume.
- 5
- Dennet, D. (1990b) ``The interpretation of Texts, People
and Other Artifacts'' Philosophy and Phenomenological Research
L, Supplement, 177-94, Fall 1990.
- 6
- Emmeche, C. (1992) ``Life as an Abstract Phenomenon:
Is Artificial Life Possible?'' in Varela, F. and Bourgine, P. (eds)
Towards a Practice of Autonomous Systems. Proc. of the First
European Conference in Artificial Life. MIT Press, Cambridge, Mass.,
1992. pp. 466-474. Online version was use: to be found at:
http://www.nbi.dk/ emmeche/cePubl/92a.liabsphe.html
- 7
- Gould, S.J. and Lewontin R.C.
``The Spandrels of San Marco and the Panglossian Paradigm: A
Critique of the Adaptationist Programme'' Proc. of the
Royal Society of London, Series B, vol. 205, No. 1161 (1979)
pp.581-598.
- 8
- Langton, C. (1991) ``Artificial Life''. Chapter 2 of
Boden, M. The Philosophy of Artificial Life, Oxford
University Press, New York, 1996.
- 9
- Maturana, H. (1978) ``Biology of Language: The
empistemology of reality'' Chapter 2 in Miller, G. and Lenneberg, E.
(eds.) Psychology and Biology of Language and Thought: Essays in
Honor of Eric Lenneberg. Academic Press, 1978, pp.27-63.
- 10
- Maturana, H. and Varela, F. (1973) ``Autopoiesis. The
organization of the living''. From Maturana, H. and Varela, F.
Autopoiesis and Cognition. The realization of the living, D.
Reidel Publishing Company, 1980. pp.63-135.
- 11
- Maturana, H. and Varela, F. (1980) ``The Tree of
Knowledge. The Biological Roots of Human Understanding'' Shambala, 1992.
- 12
- Ruiz-Mirazo, K. and Moreno, A. ``Autonomy in natural and
artificial systems'' Artificial Intellingence 117(3), 2001.
- 13
- Steels, L. (1991) ``Towards a theory of emergent functionality''
in Meyer, J. Wilson, R. (eds.) Simulation of Adaptive Behavior. MIT Press, Cambridge MA,
1991, 451-461.
- 14
- Varela, F. Autopoiesis and a biology of intentionallity.
Preceedings of a workshop on Autopoiesis and Perception, Dublin
City University 1991.
- 15
- Millikan, R.G. (1989)``In defense of Proper Functions''
in Philosophy of Science, 56 (1989) pp.288-302.
This document was done using LATEX2e ; running on Debian GNU/Linux.
The use of free software is not `just' a possible technological
choice but the condition of possibility of a technological
(cybernetic--control through applied knowledge) autonomy
Footnotes
- ... behaviour1
- the bird is digging (now) because it wants
to
hide a swarm with the purpose of recovering it when
inmediate food resources are unavailable (future)
- ... behaviour2
- Ants tend to
follow the smell of other ants, if food is found in a place ants
will
return with the food to the colony, the paht will be travelled
twice,
the smell of the path increases, the probability of the path to
be taken
by other ants increases, when taken by other ants keeps
increasing
and a collective behaviour emerges: all the ants are following a
path
towards a succesfull energy source.
- ... explanation3
- This is doubtless one of the major problems
of
functionalism.
In [5] Dennet emphasises that any trait or
mechanism is
`in principle' subjected to an arbitrary functional
interpretation.
- ... function4
- Imagine that an accidental exact copy of a system with
a proper function comes to existence (as if a copy of yourself
was to
appear suddenly behind you). In such case the exact copy
will not have any proper function if
it didn't have the history of the original system (your
accidental copy's
heart ``does not, in fact, have circulating blood as a proper
function
[sic.]''p.292).
- ... definition5
- It must be said that Millikan specifically
considers her definition to be related to purposive function and
not to
``function as'' (as the performance of an item within the context
of
a system -decompositional functionalism above). To quote an
example from
her own: ``a diseased heart may not be capable of pumping, of
functioning as a pump, although it is clearly its
function,
its biological purpose, to pump (...)''(p.294). What Millikan
wants to have is a
normative notion of function. ``The problem [she tries to
address, and
solve] is how did the atypical members of the category that
cannot
perform its defining function get into the same function
category as the things that actually can perform the function?''
(p. 295).
But categories and epistemological normativities do not belong to
entities but to subject-object cognitive relations (are not
ontological,
but epistemological, categories), thus, it is, at least,
problematic to
ground the notion of function in such relational space and
responding
to epistemological problems that do not happen to be in the
domain of
the systems under study (but of its cognitive and normative
categorization --in the domain of our understanding of them)
- ... 19786
-
According to Maturana functional explanations bring non present
features to the explanation:
the evolutionary history of an organism is not present in the
mechanisms
governing its behaviour. Functional explanations are semantic
projections
which could be metaphorically useful but ontologically
misleading.
- ... system7
- solving some (but not all) of the
problems of the adaptationist program as critisized by
Gould and Lewontin [7]
xkrop
2003-06-13