Can Development Be Designed? What we May Learn from the Cog Project

Neither design nor evolutionary approaches to building behavior based robots feature a role for development in the genesis of behavioral organization How ever the new Cog Project aims to build a humanoid robot that will display behavioral abilities observed in human infants and proposes making use of ideas from evolution and developmental psychology in its design This paper o ers a provisional evaluation of this work from a developmental perspective to show how developmental study may o er not only a source of phenomena for modelling but also a method that contributes to our understanding of how self organization works The design methodology that underlies Cog confronts problems with se lection and interpretation of component behaviors and how these may be better understood through appropriate developmental study is illustrated Principles that underlie the design of Cog are shown to exhibit interesting convergences with infant mechanisms based on the signi cance of emergent functionality and the action as opposed to representation based nature of both initial and out come mechanisms However analysis of infants yields a more constructive view of ability associated with di erent assumptions about the subject s relationship with the environment Routes to Understanding Autonomous Agents Arti cial Intelligence s new behavior based robotics is uni ed by commitment to un derstanding intelligent systems in terms of speci cs of their physical embodiment their sensorimotor coupling with the environment and the organizational possibilities of the situatedness to which these properties give rise There is less agreement as to whether Submitted to the Third European Conference on Arti cial Life Granada Spain June a historical process must be a necessary component of the construction of a system that is to become capable of survival in our normal environment Engineering methods are at the heart of a design approach to building robots attempting to pre specify component behaviors that are required and the mechanisms through which they can be implemented Brooks s insect like Creatures a b based on a subsumption architecture with layered control provide elegant and successful exam ples of this strategy Exponents of evolutionary robotics see this kind of hand design as simply too hard to be feasible at any but a toy scale however ingenious the experi menter Instead processes inspired by evolution are exploited to automate design For example notions like mutation recombination and selection have been employed to evolve sensorimotor controllers in recurrent dynamical arti cial neural networks by re peatedly evaluating and breeding sets of initially randomly generated networks thus arriving at a maximally adaptive genotype like structure Cli Harvey Husbands Harvey Husbands Cli The overall role that a historical dimension plays in these approaches to autonomous organization is more complex than it may initially seem at least as far as evolution is concerned Super cially they might appear to correspond to the distinction be tween implementation by design and implementation by evolutionary strategies that Varela identi es as one criterion of a theoretical shift from traditional symbol manipulating cognitivism focussing on the subject s representation based ac tivities in a pre given world to an enactive framework in which the subject s activities serve to construct a domain of interactions through which a world is brought forth On closer inspection the gap is smaller than it seems For example both approaches purport to reject traditional representationalist assumptions in favour of pragmatic wiring considerations in the former case and dynamical systems analysis in the lat ter Furthermore Brooks s Creatures are deliberately engineered incrementally while current evolutionary robotics pre speci es behavioral outcomes insofar as selection is achieved through evaluation procedures that depend on objective task oriented t ness functions Both approaches di er from autopoietic notions which focus on how systems generate and maintain their own organization i e are self producing and characterize evolution in terms of natural drift rather than progressive adaptation to the environment Maturana Varela Varela Neither approach features an explicit role for the individual historical dimension development in the genesis of behavioral organization However the ambitious new Cog Project aims to build a humanoid robot that will display behavioral abilities observed in the rst couple of years of human life Brooks Stein Brooks Cog is not intended to be a model of human development Nevertheless it aims at biological relevance Brooks and proposes making use of ideas from both evolution and developmental psychology Brooks Stein This paper aims to evaluate these proposals from a developmental perspective Its emphasis is on going beyond the use of developmental study as a source of phenomena for modelling to consider how it can provide a method that contributes to our understanding of self organization From Creatures to Cog The Cog Project is at an early stage so any assessment must also be of a provisional nature It aims to extend the methodology of generating complex seeming abilities through hard wired networks of simple sensorimotor coordinations each capable of engaging in independent interaction with the environment As far as possible such task achieving behaviors are to be added incrementally with each of these layers be ing tested and debugged before attempting to build in another continuing an analogy to evolution Brooks Stein p The initial schema for Cog includes far more layers than have so far been built into any Creature o ering an increased challenge for undertanding behavioral coherence Brooks These layers begin with apparently basic abilities such as visual following and sound localization and cumulate in complex ones such as generic object recognition and protolanguage For example layers most closely related to the development of prehension are body stability leaning rest ing bring hands to midline own hand tracking hand linking batting static objects grasping transfer and body arm reaching Cog will get a continuous large and rich stream of input data of which it must make sense relating it to past experiences and future possibilities in the world Brooks Stein p but it appears to follow its Creature predecessors in lacking a clearly de ned role for endogenous organizing mechanisms Attaining novel abilities by building in additional layers is the consistent focus in preference to more dynamic notions of designing the system so that novel abilities might come for free as far as the design process is concerned emerging from what happens when implemented layers are allowed to run in the environment For example when it is assumed that functional behavior layers for correlating hearing and vision should serve as a usable basis for discrimination between interesting events and background noise this is use more by the human designer than autonomously by Cog as part of an internal process of self organization Cog Evolution and Development Basing layered control on an analogy with evolutionary development Brooks Stein could be seen as implying a view of the evolution development relationship based on the notion of terminal addition The implications of this view are illustrated by a model that views Piagetian stages of intellectual development from sensorimotor abilities to abstract thought in terms of evolutionary selection pressures operating on genotypes that make possible speci c behavioral adaptations Parker Parker Gibson Cross species observations of relative attainments on developmental stages of ability are used as evidence that ontogeny recapitulates phylogeny based on a series of terminal additions of new structures or stages through evolution The fundamental argument is that more intelligent species achieve their greater intelligence not by altering early developmental processes but by adding later stages of intelligence to the end of the developmental cycle Gibson p This view contrasts strongly with the epigenetic position favoured by Piaget e g the origins of whose developmental stages it purports to explain insofar as he considers stages as evidence for levels of knowledge that are neither additive nor ge netically predetermined but the product of developmental processes that operate from the very outset While Piagetian stages and developmental processes are contentious there are good grounds for sharing his dissatisfaction with proposals for genetically pre speci ed additive sequential behavioral outcomes that arise from this way of us ing orthodox neo Darwinian theory to frame an account of development Attributing a privileged role to genes in the determination of development commonly enshrined in the genetic program notion has appropriately been criticized as denying the very development that it seeks to explain Oyama Genes can be thought of as in putting certain parameter values into a developmental process involving a system of multiple variables and relations but they do not de ne the organizing principles of that process Those depend on the dynamics of the developing system as a whole Goodwin Observations of human acquisition of everyday apparently universal sensorimotor abilities suggest processes capable of exible outcomes that strain the notion of genetic predetermination For example infants who are raised with sparse adult interaction may not walk even by around years of age Instead they acquire scooting sitting while using arms to pull the body along a behavior whose form is surely not pre programmed Dennis Brooks and Stein acknowledge that the analogy between layered control and evolution is simplistic and crude and seem unlikely to wish to characterize devel opment in the over simple additive genetically bound terms sketched above Their current models however appear compatible with that direction The evolutionary ap proach to constructing robots is sensitive to the fact that its current models locate the form of individual performance too exclusively in the genes and both approaches agree on serious reservations about viewing real evolution as an orthodox process of optimi sation with contemporary animals seen as solutions to problems posed in their species distant evolutionary past Brooks Cli Harvey Husbands However just how new sensorimotor coordinations emerge in development if not through an es sentially additive sequence of gene behavior mappings remains an open question Some developmental ideas about how transactions between phylogenetically determined ini tial mechanisms and the environment may guide ontogenetic change are sketched in the following section of this paper Using Developmental Observations Constructing Cog by design entails pre selection of behaviors into which its abilities will be decomposed Its planned layers thus embody an implicit developmental theory to the extent that they highlight a restricted range of the behaviors that have been studied by developmental psychologists and provisionally order them so that earlier layers are expected to aid the implementation and operation of later ones Brooks s work emphasises the di culty of achieving an e ective behavioral decom position of abilities and how we may frequently be misled into thinking that our observers discriminations map straightforwardly onto demarcations in our subjects mechanisms Certainly the selection and interpretation of behaviors for such a design plan raise closely related problems On the one hand behaviors that are necessary to the developmental sequence may be missed In the case of prehension for example arm raising behavior is commonly found after batting objects is observed but before top level reaching appears while the infant intently xates the object the arm and hand are raised in its direction and held at the horizontal often with signs of consid erable e ort This behavior is not included in the Cog schema although it may play a more signi cant role in the emergence of reaching and grasping than say hand linking Equally of course it may not Deciding which is the case depends on interpretion of the behavior concerned that requires a hypothesis or at least a hunch as to what mechanisms are involved which clearly a ects plausible implementation strategies The di culty of such interpretation as far as individual behaviors are concerned can be illustrated easily without considering potential Cog layers that have controversial psychological connotations e g that dedicated to multiple drafts emergence associ ated with Dennett s ideas about consciousness What is the signi cance for example of the readily observable behavior of bringing hands to the midline There is no de velopmental consensus as to why infants exhibit midline activity Rutkowska b Possible interpretations range from initially out of sequence ne motor movements that will eventually be used for manipulating grasped objects to stress reduction in the case of hands brought to the mouth and a side e ect of the mechanics of failed early reach ing attempts Likewise is batting at objects a form of ballistic reaching superseded by reaching with visual feedback or is it an attempt to palpate an extended surface that is perceived as too large for grasping A prime source of such di culties is methodological Much mainstream develop mental psychology does not itself employ a particularly developmental method It tends to concentrate on relatively isolated behaviors is preoccupied with when in the subject s chronology those behaviors appear and with judgments of success failure that treat behavior as a mere criterion of some other supposedly underlying ability And it generally works backwards from possibly erroneous assumptions about outcome behaviors to processes of acquisition Rutkowska Faced with the question How do you get from A to B it concentrates too exclusively on the nature of B An es sential change of focus is needed from initially asking Can this system do B to the more fundamental question What is this system doing This change of orientation is facilitated by employing a more genuinely developmental method The strategy involves three things that enrich and often alter our understanding of the nature of B Taking behavior seriously by looking at the patterns through which it achieves succeed fail outcomes in terms of the observer s criteria Working forwards by taking seriously the idea that you can t get from A to B unless you start from a good idea of what A is Observing changing behaviors in a domain of activity using the relative position of a behavior within a sequence to constrain its interpretation Behavioral Interpretation Through Development The developmental strategy can be illustrated by looking at infants changing perfor mance on a simple visual tracking task that presents them with a moving object part of whose path is hidden by an occluder Rutkowska a c Their looking behavior is generally assumed to index knowledge of the object and of its motion suc cess look to exit as before the object reappears failure look elsewhere Even very young infants will sometimes succeed in anticipating the object s emergence from behind the occluder in an operational sense by looking at the exit side as or before the object comes back into view Should we therefore conclude depending on theo retical preference that infants come equipped with visual procedures for solving the problem of object search or believe that objects continue to exist while out of sight Considering the details of this behavior in the context of others displayed by and month old infants makes such interpretations extremely implausible Three aspects of the data are notable The behavior pattern of xations and head and eye movements that sometimes leads month olds to be looking at the object s reappearance point before it comes into view is quite di erent from the pattern through which month olds attain the same outcome While month olds simply continue tracking as the object disappears from view sometimes tracking as far as the reappearance point month olds characteristically pause as the object disappears from view then make a single head and eye movement to the reappearance side of the occluder which they xate until the object returns to view Although month olds continued tracking has the appearance of functional search for the disappeared object its frequency declines rather than increasing with age Nor is it simply replaced by a corresponding increase in the entry exit xation pattern found in month olds despite infants getting faster and faster at turning to re xate the reappearing object from wherever they do happen to be looking as it comes into peripheral vision month old subjects exhibit less of either form of successful anticipation than or month olds demonstrating the kind of U curve that characterizes many instances of development What does increase are behavior patterns involving attention to the object s dis appearance point The one most characteristic of month olds can be described as backtracking as the object disappears the infant continues tracking but then turns head and eyes sharply back to xate the object s disappearance point This is a strange observation as far as attempts to interpret backtracking in isolation are concerned since those generally assume the infant must have noticed some change in the reappearing object and be looking back to the disappearance point where the original object was last seen Here however a single object moving at constant speed is involved and is generally still out of view when the infant turns back These and other aspects of the data suggest the observer labelled tracking task is not initially a problem with the goal of nd the object as far as the infant s viewpoint is concerned month olds behavior is not wired up to search for objects that move and disappear but they are initially equipped with a preadapted behavioral procedure for tracking visible object movement Their continued tracking is no more than a failure to alter ongoing behavior when environmental circumstances change They fail to do so because the recurrent visual pattern kinetic occlusion that marks the moving object s disappearance has yet to become salient to them It may be available preattentively at the sensory process level but has yet to be usable at the level of action through coordination with behavior If this is the case we would expect month olds to do one of two things when the object moves out of sight nothing i e look away or lose interest or what they are already doing i e continue tracking These prove to be the behavior patterns that are most characteristic of that age month olds backtracking can be seen as indicating the beginnings of attention to kinetic occlusion which develops further with behavior patterns such as intently xating the object s disappearance point during the entire period that it is out of sight They are not seeking a changed missing object Only the month olds coordination of attention to kinetic occlusion with turning to look to the opposite side of the occluder marks the beginnings of search from both the observer s and the infant s viewpoints Infants then are not initially trying to do the task as an observer sees it Their changing performance is more akin to task construction than task solution Through repeated sensorimotor interactions with the environment they come to construct the problem of search for missing objects through their experience of nding them Even at this everyday level development may be seen as an enactive process in Varela s terms insofar as its processes appear to be directed at problem de nition rather than problem solving Action Based Task Construction The broad issue of how novel abilities are constructed can be crudely divided into three questions each of which allows additional evaluation of the architectural principles and design methodology of the Cog Project from a developmental perspective What are initial mechanisms like What is the process through which they change like And what do they change to Emergent Functionality in Sca olding Development A key point of rapprochement between design and developmental methodologies in volves the notion of emergent functionality through which complex abilities may re sult from the independent interaction of more basic components with the environment Emergent functionality is central to the Cog Project s attempt to maintain behavioral organization through layered control and it may be developmentally advantageous in two ways at least as far as the early stages of acquiring novel abilities are concerned cf Rutkowska a c Firstly emergent functionality could support an initial organization of independent sensorimotor coordinations such as the visual following featured in the preceding sec tion that is neither a tabula rasa nor a blanket prewired solution to problems that will be encountered This would o er preadaptation without rigid predetermination Interactions between preadapted abilities of such a system and the environment in which it nds itself could enable it to tune in sensorimotor coordinations and se quences of such coordinations that prove viable in the individual s experience Novel coordinations e g locomotion by scooting would not be precluded in case of al tered environmental conditions and or properties of the subject e g physical motor disability Secondly within the developmental process the phenomenon of sca olding can be viewed as a form of supervised learning in which emergence of function is temporarily engineered to establish the developmental space within which viable patterns of ac tivity can be stabilized Sca olding as originally viewed in social terms marks the process through which more able humans manipulate the infant s transactions with the environment so as to foster novel abilities e g Valsiner Wood Bruner Ross The process begins with sensory and motor processes that are not coordinated by the infant but are set in alignment with the environment by adults For example if an infant s head is moved to look at someone leaving a room and simultaneously his her hand is moved up and down whatever the infant is doing initially s he is not waving goodbye Key features are customizing or simplifying the environment reducing the number of degrees in the target task directing attention by marking critical attributes and enabling repeated experience of the end outcome or goal of an activity that the infant would be unable to seek voluntarily This sets up the possibility of serendipitous learning by the infant that is of an accidental i e unplanned yet fortunate discovery of possibilities for e ective action in which the balance of behavioral control shifts from the environment to the subject The ubiquitous nature of such phenomena has been seen as evidence for all aspects of human development being socially and culturally guided but adults may be exploiting and directing inbuilt processes that also operate in infant s spontaneous interactions with the environment For example in the previous section s account of the devel opment of visual tracking initial serial ordering of behaviors emerged from ongoing interaction with the environment it was not governed by a goal or plan directed at nding the disappeared object Spatio temporal properties of the infant s interactions with the environment supported recurrent sequences of sensory and motor processes most notably attention to kinetic occlusion followed by turning to re xate and hence to experience nding the reappearing object In principle such processes may share the main properties of social sca olding provided attention can be limited through processing restrictions such as spatiotemporal constraints for a relevant simulation of an attention mechanism in the context of sensorimotor learning see Foner Maes The notion of sca olding begins to provide a way out of problems faced by traditional AI s view of learning This tends to see it in terms of adaptive change that enables a system to do a task better next time round and which is unnaturally di cult unless the subject knows the goal in advance Mitchell Such assumptions make it di cult to see where novel abilities and goals might come from It is notable that a robot system such as Darwin III which is purported to exhibit self organization in the absence of supervision and with unbiased internal connectivity in place of inbuilt sensorimotor structure relies heavily on designer coded value shemes that evaluate the outcomes of its behavior Reeke Finkel Sporns Edelman These intrinsic value schemes e g getting visual stimuli onto the fovea good making contact with bumpy objects bad hand in region of foveated object good share non trivial properties with traditional internal goals and with externally speci ed tness func tions hence encounter similar problems As a means of ensuring recurrent experience of novel viable activities coupling emergent functionality with sca olding may o er a better characterization of constraints on infant s changing behavior Is Development Additive The kinds of behavioral developments that characterize the rst year of life appear to involve more than straightforward addition of novel sensorimotor coordinations In many domains of activity there appears to be a move away from a reactive mode which is essential to the basic operation of layered control in Brooks s robots to increasingly anticipatory functioning and what might be called nascent plans In the case of visual search for example the infant develops from attention to kinetic occlusion plus turning to xate the reappearing object to attending to kinetic occlusion then turning in order to re xate the reappearing object An explanation of the novel mechanisms that underlie such changes need not invoke qualitative change in the form of concepts or mentally represented goals controlling behavior It will need to account for an extended time scale of coupling between the subject s activities and the environment and the changing functionality of sensorimo tor components that is illustrated by eye and head movements initially associated with xation coming to be used also for re xation Traditional computational explanations could permit new and old programs to invoke common lower level movement prim itives It is however an interesting empirical question as to whether and how an intricately hardwired subsumption architecture could generate such phenomena What Do Internal World Models Model Meyer Guillot refer to anticipatory triples of the form if in sensory cir cumstance I do behavior B I shall get sensory circumstance as internal world models While agreeing that such mechanisms underlie a form of nascent planning it is worth emphasizing that to the extent that they model anything it is constraints on e ective action rather than an external world in which action takes place De velopmental psychology and cognitive science have become relatively xated on the notion that model like internal representations of the environment underlie intelligent functioning a notion that is not endorsed here Nor are representations featured in Brooks s b foundational assumptions about intelligence although it has been argued that his robots may in fact use internal representations and require them for further progress to be made e g Clark Toribio I doubt this conclusion as far as both infants and robots whether humanoid or oth erwise are concerned This is not because there is no interpretation of representation that can be mapped onto their functioning but because the notion of an internal rep resentation attempts to demarcate one component of a complex subject environment system and to give it a privileged status in the genesis of organization In doing so it limits attempts to deepen understanding of how that organization is achieved Insofar as it works to establish selective correspondence s between subject and en vironment action maps onto some perfectly good treatments of representation and the establishment of meaning which are equally applicable to human infants to Brooks s Creatures and by extrapolation to Cog Rutkowska a c What these action based process oriented approaches share is a scale of analysis that spans sensory and motor processes and their functional coordination in the environment unlike tradi tional preoccupations with representation as a substitution for the environment which locates it rmly in the head A typical direction is the situation semantics notion of attunement to constraints Israel which allows infant sensory motor coordina tions such as reaching towards or avoiding things and the task achieving behaviors of Brooks s robots e g b to be thought of as underlying human and robot subjects representation and understanding of constraints on acting in the world and their abil ity to satisfy them Also signi cant are Dretske s notion of a natural system of representation which can be applied to cases of infant action as when very simple directionally selective elements acquire the function of indicating that something is approaching from the way they are wired with avoidance behaviors and to robots as when a sonar pattern associated with free space acquires the function of indicating a place to visit when wired into a task achieving behavior that successfully embeds the robot in its environment Also applicable is Varela s view of meaning emerging from processes that establish domains of interaction between a self and its environ ment for which the CNS s sensory motor and inter neurons are only one specialist adaptation for achieving closure a re exive interlinking of subject and environment processes that supports construction of neurocognitive identity As far as such systems are concerned Explicit internal models of an objective external environment are unnecessary to adaptive behavior provided embedded sensory and motor processes are taken as the scale of analysis The usefulness e ciency of sensory processes lies not in how exhaustively they enable the subject to model an object or an event but in how successfully they limit and allow for possibilities for action No bit of action mechanisms is the internal representation The capacity for successfully locking onto the environment and anticipating the consequences of activity within it is distributed across the operation of perceptual and behav ioral processes For example infants knowledge of invisible object movement is embedded in the way the disappearance event becomes involved in determining future head and eye movements towards the reappearance point The notion of representation when viewed in terms of action based mechanisms does no explanatory work in the sense of being a more or less localizable func tional component of action Representation whether by selective correspondence or by substitution is one vantage point onto processes that are grounded in an action system spanning subject and environment It makes equally little sense to consider this a central internal phenomenon or an external one When it comes to considering the environmental contribution to the interaction of subject and environment it seems that Brooks s methodology does not fully follow through the implications of this systematic action based approach Whereas tradi tional representation was appropriately dismissed its opposite number information is invoked in vestigial but non trivial allusions to animals having sensors that extract just the right information about the here and now around them Brooks a Despite a subjective focus on embodiment and action a notion of an objective en vironment containing information for action is brought in albeit information that is selected with the subject s action requirements in mind This can raise inappropriate assumptions about the subject s access to the world In the context of challenging model like representations work in behavior based robotics has often alluded approvingly to Gibson s theory of direct perception and the notion of a ordances invariant combinations of properties that specify what things are for for a given subject It is often unclear just how far this irtation with ecological psychology s methodological realism is intended to go Buying wholeheart edly into the view that there is an organized world of objects and events independent of the subject s activity and that this is the world that is perceived and known risks simply substituting a discredited notion of internal representations about the world for equally dubious external information about the world as the foundation for organiza tion This can only be counterproductive as far as establishing a genuinely systematic account of adaptive behavior is concerned cf Bersini It can make for easier questions for robot design and for development though they may not be appropriate questions To understand a subject s world we do not need to ask how organization is constructed only about what objects and events they are sensitive to and about what information speci es those things Likewise development is not a constructive process but one of coming to perceive better through the education of attention to things that are already out there If we reject the information pickup recovery metaphors for perception and assume the environment may not come ready populated with the categories of objects and events about which language using scientists and philosophers routinely speak there may still be no need to be pessimistic about how we might talk about the environment If the aim is to understand emergent organization within an environment as opposed to what is really out there beyond the subject and the subject s activities behavior based robotics suggests some interesting possibilities One route comes from evolutionary robotics focus on the adaptation of simple robots in simple environments e g Cli Husbands Harvey The power of this method lies in its potential for reverse engineering to clarify what sensorimotor con trol structures the robot evolves for itself in place of checking its success failure in acquiring the categories of its creators A further direction involves turning the issue of what sensors are doing away from the heavily entrenched notion that they provide environmental information whether for direct action control or further processing Dynamical systems theory may support a promising alternative if it can develop the notion that sensors are not measurement devices It suggests that sensor signals need not encode information specifying particular states of a robot in its environment it is enough that they vary in some way that depends upon the dynamics of the robot environment interaction Smithers p delivering what might be con sidered sensorimotor invariants This kind of re think may provide an original route into genuinely enactive mutual notions of organization