Computation Dynamics and Sensory Motor Development

Outside Piagetian theory sensory motor co ordinations are often relegated to the domain of mere motor skill but their development shares important features with that of cognitive structures This paper focusses on early action to assess the prospects for an account of development that is based on a system s initial mechanisms and processes of interaction with its environment without prespeci cation of stable patterns of organization that will be acquired A truly epige netic account proves elusive with empirical ndings increasingly being taken to indicate preadaptation and strong domain speci c constraints on infant abilities Despite this evidence can be marshalled for variability which is compatible with a general purpose process of internally motivated and structured organizational change However the mechanisms underlying this process are obscure Clari cation is sought by considering current attempts to understand sensory motor co ordination through the construction of arti cial agent environment sys tems Disappointingly such approaches often share a need to incorporate an explicit bias towards the recurrent behaviour patterns that will come to have func tional signi cance for the systems they aim to explain Synchronic systems in this vein exploit predesigned sensory motor connections with the environment Their diachronic counterparts feature designer speci cation of acceptable outcomes for activity in the form of problem speci c tness functions or goal like value schemes that are credited to evolution Neither computational nor dynamical systems con cepts provide an automatic escape from this problem but most promising may be robotics approaches informed by dynamical systems theory that challenge main stream views of information and information processing Paper presented at the symposium on Modelling Epigenetic Emergence convened by Jan Boom Utrecht and Peter Molenaar Amsterdam Penn State for the Piaget Centennial Conference The Growing Mind Multidisciplinary Approaches Geneva September Reviving epigenetic issues The structures of knowledge do indeed achieve necessity but at the end of their development without having it from the start and do not involve any antecedent programming Piaget p Piaget speaks here of formal properties of operational thought and genetic programs but his general concerns are equally relevant to the kinds of sensory motor co ordinations that many have relegated to the domain of mere motor skill and to the role of com putational approaches in explanations of development Increasingly the preoccupation of much mainstream infancy research with between the ears cognition is being challenged by the view that mind is grounded in action e g Rutkowska Thelen Smith Whether action is seen as a precursor of cognition or action cognition as a mistaken opposition action and cognition pose identical problems Those problems mark an interdisciplinary revival of Piaget s tradi tional concerns What kind of processes give rise to developmental outcomes that are not predetermined however predictable their acquisition appears to be Can an action based epigenetic approach to development surpass and supplant inadequate nativist or empiricist accounts of our knowledge of the world In this paper I shall be looking at these problems from the standpoint of apparently simple sensory motor acquisitions Two points are especially pertinent to establishing the broader relevance of this perspective Acquisition of everyday sensory motor activities meets criteria that have been pro posed for strongly constrained knowledge structures and taken to support Chom sky s nativist view of natural development as a form of growth that is guided to a predetermined end by domain speci c preadaptations Keil Activities such as locomotion and prehension exhibit mapping from a wide range of experience onto a narrow range of outcome structures they appear to be rapidly universally and e ortlessly acquired without formal tutoring the psychological mechanisms underlying them are relatively closed to introspection and there is a strong sense of anomaly with violations Rutkowska Despite this apparent universality evidence for variability in the form of develop mental acquisitions questions the extent to which they are prespeci ed Flexibility is exhibited at the level of movements as when locomotion is attained by sitting cross legged and using the arms to pull the body along in scooting Dennis body parts as when prehension via legs and feet routinely replaces arm hand use in di erently abled thalidomide subjects and sensors involved as when feeling a surface substitutes for seeing depth in control of crossing behaviour on the visual cli Rader Bausano Richards The explanatory framework that I shall explore features recent computational work that shares developmental psychology s growing focus on action and emphasises the ne cessity for models of whole agent environment systems The attempt to understand developmental processes through computational ideas is far from new In Simon suggested writing a general purpose learning program that would operate on other pro grams to generate the kinds of organizational change that Piaget attributed to equilibra tion But although Simon s notion may be a useful metaphor for describing a system s potential for adaptive change the extent to which it can explain such change is ham pered by its use of classical computational concepts in a traditional way especially the idea that change must implicate a distinct mechanism component that is dedicated to doing the changing This is precisely the kind of idea that recent computational work challenges In the next section I brie y outline some basic assumptions of this work by locating them in their historical context I also draw attention to what I consider to be a persistent source of di culty for our attempts to frame novel theories from computational or psychological directions Self organization and the R words Computational approaches associated with traditional cognitivism have predominantly attributed intelligent systems knowledge of the world to internal representations of an objective external reality viewed as symbol structures that make explicit information about objects their properties and their location with regard to one another and to the subject Programs which specify rules for manipulating these structures govern the reasoning processes for formulating goals and planning behaviours that are identi ed with the core of the mind s activity So better explicit exhaustive representations should yield more knowledge and better general programs should yield more ways of deploying that knowledge In practice systems built along these lines prove to be notoriously brittle a system may be good at a game like chess but will be stopped in its tracks by encountering even another game environment It seems virtually impossible to get into a single system all the knowledge and program rules that seem necessary for exible adaptive behaviour Subsequent computational work in parallel distributed processing or connectionism aims to improve on the traditional computational picture by characterizing cognition at a subsymbolic level in terms of multiple interconnected simple units operating in parallel cf neurons though how appropriately is debatable Computation as xed sequential programmed rules is replaced by the whole network settling into a stable pattern of activation by trying simultaneously to satisfy many soft or weak constraints that are only meaningful if considered collectively Compared with traditional computational systems connectionist networks have achieved relative exibility on some tasks under noisy or variable circumstances by settling into the most likely of a range of related solutions with pattern discrimination or categorization considered one of their great implementational successes Two attempted shifts are in evidence here Increasing concern with emergent properties For example rule like behaviour is attributed to patterns of activity that recur within a network not to operation of a pre existing program Increasing exploitation of self organizing properties Notions like settling into a solution move the focus from program design towards interest in how systems gen erate and maintain their own organization i e are self producing or autopoietic in Maturana and Varela s sense Computational work that focusses on whole agent environment systems aims to go even further in these directions Its emphasis is on putting action and cognition into context as processes of physically embodied systems that are embedded or situated in an environment Classical systems mistakenly used the in principle separation of program and physical machine to licence total disregard for the physical circumstances of the cognition they attempted to model Connectionist systems too are limited Despite pleas to biological plausibility they remain far from modelling real life deployment of mental processes or development Their sensory interfaces with environmental inputs rarely consist of intensity arrays tending to involve experimenter selection and hand coding to a degree that questions the label self organizing networks generally model or simulate only isolated subsystems rather than being part of a whole system that is embedded in a real environment and their changing organization relies extensively on explicit external feedback about the correctness or otherwise of outputs In a signi cant sense their designer s experimenter s activities constitute their environment closing the loop between their input and output units By way of contrast the autonomous agents direction aims to shift the research focus more strongly towards self organization by building robots that are left to their own devices in real environments or at least simulating such complete agent environment systems and by capitalizing on the unique forms of emergence that this embedding of cognitive and physical processes may support A key success of this new computational direction has been its contribution towards dismantling the Cartesian mind body dualism that pervades much of cognitive science But there are many dualisms Costall aptly appropriates one of Benchley s apho risms that there are two kinds of people in the world those who believe that there are two kinds of people and those who don t for the psychological case the world can be divided into two kinds of psychologists those who know they are committed to some form of dualism and those who don t The insidious dualism to which I wish to draw attention here is that of subject environment We should make this distinction far less readily than we do As observers we generally make it in physical terms skin or tin boundaries demarcate the limits of the subject in their environment What is needed is a good process oriented language that spans the joint roles of subject and environment in generating functional activity What we predominantly have is a resolutely linear directional in out view of environment s rela tion to mind Senses and motors are physically spatially separable interfacing with the environment in di erent places hence the processes they implement are separated too It is remarkably di cult to escape the worldview that sees the senses as the front end of any intelligent system with its motor capacities bringing up the rear as its output A system uses its senses to get information from the environment then determines how it will act Constraints on adaptive action are mis localized in either internal cognitive structures or external task domain ones This directional in out treatment of sensory motor and cognitive functioning supports not only the traditional nativist empiricist split but also contemporary debates about the relevance of representation to valid accounts of adaptation and intelligence I have coined the expression the R word to capture the emotive tone of a good deal of the anti representational discussion coming from new computational approaches And discuss elsewhere how these objections are appropriate for re presentational mechanisms that substitute for the environment but irrelevant to action based mechanisms that support representation by selective correspondence e g Rutkowska a b What seems to be missed however in eagerness to emphasise the signi cance of environmental embedding for e ective functioning is the implication of implicitly endorsing another R word realism which is behind assumptions that environmental information can replace representation For example connectionism s new look for cognition is not so radical as to move away from divisions into input output and intervening units or to move beyond recovery or discovery metaphors for the subject s relationship to information Even highly in uential whole agent research such as Brooks s intelligencewithout reasoning representation robotics approach assumes that animals sensors extract just the right information about the here and now around them If our aim is a genuinely epigenetic framework then pleas to a privileged precursor of the subject s knowledge in external environmental information are no improvement over allocating this privileged status to the subject s internal model like representations A key dimension of epigenetic explanations as viewed from the vantage point of Varela s enaction framework is that the subject s world is brought forth through a history of structural coupling between organism and environment not pregiven in one or other component of this system For example Varela contends that information is the phlogiston of cognitive science repeatedly invoked as a source of pregiven order outside of the subject s activities Getting to grips with emergent phenomena in action entails moving beyond our en trenched ways of considering the subject environment relationship Action needs to be treated as a systematic concept that refers to functional co ordination of sensory and motor processes in the environment not to one bit of the operation of this subject environment system e g isolated motor processes or overt behaviour Rutkowska The following sections of this paper follow up this line of reasoning by looking at key aspects of agent environment systems that start out with unbiased sensory motor con nections Such systems are often based on the assumption that human design of e ective sensory and motor connections is too hard to succeed at any but a trivial scale and that developmental evolutionary techniques must be tried instead see Rutkowska for comparison of these strategies Two issues are addressed Can functional sensory motor connectivity be achieved by such systems What have they acquired once they ve achieved it