As we have argued above, cognitivist models aim at a view of action awareness in which the experience of agency arises as an intrinsic aspect of action itself (at least in the case of the pre-reflective feeling of agency). It is arguable whether this attempt could be successful, given that it relies on the explicit construction of internal representations from brain-side computations that may or may not be required for the sense of agency. We propose here an alternative that synthesizes three different theoretical developments, each of which views the cognitive agent essentially as an integrated ecology of sensorimotor skills. The starting point is a dynamic interpretation of the sensorimotor approach, which points the way towards a world-involving and non-representational account of experience. This is enriched by the enactive notion of minimal agency, which we argue is required to explain how subjectivity can arise at the sensorimotor level. Lastly, a dynamical reinterpretation of Piaget’s theory of equilibration will allow us to account for the different aspects of the sense of agency.
Dynamical, non-representational account of SMCs
We agree with the premise that the co-occurrence of actions and their typical sensory consequences (i.e. sensorimotor contingencies), as well as a sensitivity to non-typical consequences, are necessary preconditions for the sense of agency, as they may enable a momentary and implicit distinction between self and environment. However, this idea can be developed in a non-dualistic and non-representational manner, in which agency experience is truly intrinsic to the performance of actions themselves as they form part of self-asserting sensorimotor structures and relations, rather than derived through verifications and inferences using pre-given criteria as to what does and does not belong to the self.
According to the sensorimotor approach (O’Regan and Noë 2001; Noë 2004), perceptual experience, such as seeing an object, does not derive from internal representations in the brain, but is constituted by the skilful use of the regularities governing active exploration of the world. More specifically, perceiving consists in the exercise of practical mastery of the laws of sensorimotor contingencies (SMCs), i.e. of the lawful regularities in the sensorimotor flow that govern intentional interaction with the environment. Both the “content” and form of experience, i.e. what is perceived and how, is constituted by the embodied know-how of the relevant SMCs put into practice. The experiences associated with the various sensory modalities, or with distinct aspects of the environment (e.g. colours or sounds) differ, because there are different sensorimotor regularities involved in, say, seeing and hearing.
Our proposal is to extend the sensorimotor approach to the experience of oneself as an agent. On this account, the sense of agency is not something derived from internal representations of our own action-related processes. Rather, it is essentially another dimension of our relation with the world, and derives from the ways in which we establish, lose, and re-establish meaningful interactions between ourselves and our environment. In the same way that certain regularities in the sensorimotor flow associated with the enactment of SMCs determine the qualitative character of perceptual experience, certain features of the processes underlying the mastery and deployment of SMCs determine the character of agency experience.
We should note that when we talk about SMCs here, we refer to a specific dynamical interpretation of the concept (Buhrmann et al. 2013). This interpretation allows for the distinction between different kinds of SMCs, two of which are of particular relevance in the current context: sensorimotor coordinations and strategies. Sensorimotor coordinations describe particular sensorimotor patterns that are reliably used in performing a task. These can be cycles or transients in sensorimotor space and depend on an agent’s environment, body, inner activity, and the task-related context. Sensorimotor strategies or schemes are organizations of several sensorimotor coordinations that the agent deploys to achieve a given task and which are subject to some normative framework (for instance, considerations of efficiency).
Crucial for the development of our proposal is that individual SM structures do not exist in isolation. Rather, they are integrated in a complex network of interdependence. For example, my going to work may require that I first pick up my keys in the kitchen, lock the door, enter the car, drive to the office, and so on. At the same time, the sensorimotor scheme of picking up my keys is required in other contexts, such as going to buy milk from the corner shop. Everyday skilful coping thus relies on the deployment of a network of interlocking sensorimotor schemes.
What do we mean by deployment of SMCs? How exactly does a subject engage a particular SM scheme in his repertoire? For example, sitting at my desk, what determines whether I reach for the mouse to open my inbox in response to an incoming email, or rather for the glass of water to quench my thirst? Here we outline a plausible answer. Though constitutively involving the environment to close the sensorimotor loop, the use of SMCs is supported on the brain side by metastable neurodynamic structures in conjunction with metastable states in other non-neural systems in the body (see e.g., Tognoli and Kelso 2014). Like, for example, dynamic fields (Erlhagen and Schöner 2002; Schöner and Dineva 2007) such neurodynamical patterns may be characterised by a continuous distribution of activation. One may imagine the neural assemblies supporting different schemes as exhibiting localized peaks in this distribution, for instance (say, one for mouse control and one for grabbing the glass). If the activation of any such peak is large enough, the corresponding scheme is engaged, i.e. the neuro-dynamics engages the motor system. If the environmental conditions are supportive, and the motor system is in a compatible state (e.g., not prevented from moving), then the corresponding scheme is enacted by the agent.
Different sources of activation may prime individual SM schemes by raising their excitability, such as internal signals related to volition and readiness (or my thirst), as well as environmental affordances (the presence of the glass or computer mouse). The activation-threshold model is just one possible way of conceptualising this relation between different metastable neural and bodily states, rich in potentialities, which according to the circumstances can get differentially actualised in the initiation of a particular action. Other models also fit this account in terms of critical states (see e.g., Kostrubiec et al. 2012; Wallot and Van Orden 2012). In a general sense, the enactment of a particular SM scheme depends in normal circumstances on a resonance between external and internal conditions related to the agent’s desires and needs. Bodily states, history, dispositions and external factors may resonate with the water-drinking scheme more intensely or sooner than with the email-reading scheme, and it is this resonance between agent and world that breaks a symmetry in the critical state and tips the balance. As the agent is involved in regulating its coupling with the environment, an activity that in turn affects its own states, it is conceivable that some agents may be able to influence the process of selection of SM schemes, as a form of higher order regulation. This may take place through environmental mediation (e.g., the arrangement of a work-environment to encourage “good habits”). But it may also involve internal “gestures” that differentially amplify specific neurodynamic patterns. This is clearly the case in agents possessing linguistic abilities and capable of using them for their own self-control (Cuffari et al. 2015). On lower levels this may include the kind of volitional, readiness or appetitive signals mentioned above. In both these cases–via alterations in the world, or via internal gestures–the whole agent is involved in the process by encouraging certain SM schemes to resonate with the situation while others are avoided or suppressed (see also Fuchs 2011).
The idea as sketched so far is not yet sufficient to address the weaknesses we have identified in the comparator model. This is because the SM approach explains the origin of differences between sensory modalities or instances of perceptual experiences, but as Thompson (2005) has noted, it does not address the question of why we have experiences at all, i.e., the problem of creature consciousness. In the same way that a self-guiding missile, despite claims to the contrary (O’Regan and Noë 2001), does not have genuine mastery of airplane-tracking, and hence no genuine perceptual experience of “seeing” airplanes, the sensorimotor account alone is insufficient to describe the kinds of systems that can experience themselves as agents. What is missing, we argue, is an explicit notion of sensorimotor agency, i.e. a naturalized concept of a sensorimotor-based subject, with an intrinsically defined perspective, able to engage in intentional actions subserving her desires and norms. It is necessary but not enough to claim, as Hutto and Myin (2013) do, that “the phenomenological character of experiences must, ultimately, be understood by appealing to interactions between experiencers and aspects of their environment” (p. 176–77). Even if it was true that by defining phenomenological experience, such as of oneself as an agent, exactly as a relation between the acting subject and its environment, one may thus avoid having to explain the otherwise mysterious transition from mere physical happenings to an agent capable of experiential phenomena, this would only reframe the problem as the question of what an “experiencer” is in the first place, i.e. what is it about such entities that they can have experiences. We suggest that an enactive framing of the sensorimotor approach can resolve this issue.
We propose that the origin of a first-person perspective, a prerequisite for talking of a system enjoying experiences, is the emergence of sensorimotor agency. By this we mean an entity whose constitution implies a unique and intrinsic perspective on the world; or rather, an entity that, through its self-constitution, brings forth its own domain of relevant interactions, or Umwelt in von Uexküll’s (1934) terms. This is most easily understood in analogy to biological agency. From an enactive perspective, the simplest living organisms already exhibit a form of agency. Unicellular organisms, for example, are complex networks of precarious, co-dependent chemical reactions, in which the activity of the whole network is necessary to prevent the component processes from running down. These cells are agents in the sense that they can regulate interactions with their environment in a way that support their continued existence (e.g. by regulating osmotic pressure). Otherwise neutral external affairs thus gain a valenced status with respect to the cell. What is good or bad for it is not arbitrarily defined by an external observer, but is intrinsically determined by its processes of self-constitution. Thus, unicellular organisms can be said to enjoy a certain subjectivity or perspective in the sense of “sentience, the feeling of being alive and exercising effort in movement” (Thompson 2007, p. 161, see also Jonas 1966; Sheets-Johnstone 1999; Margulis 2001).
Barandiaran et al. (2009) have synthesized this idea into an operational definition of minimal agency that is captured in three individually necessary and jointly sufficient conditions. The first is individuality, the requirement that through its own activity the system distinguishes itself from its surroundings in a non-arbitrary fashion. Organizational closure, a relation between component processes in which each precarious process in the system is enabled by and in turn enables at least one other process, is one way a system may realize its ongoing individuation.
The second requirement for agency is interactional asymmetry: the system’s ability not merely to passively suffer exchanges, but to actively modulate its interaction with the environment. This is what we normally mean when we talk about agents performing a move, rather than simply moving or being moved. Instead of being an equal partner in the mutual coupling with its environment, the system is, at least in some cases, the true source of activity, i.e. in some way responsible for, or the agent of, this activity. Note this does not imply that interactional asymmetry has to be exercised all the time. Some actions might involve active regulation only initially or intermittently. And at times an agent may passively undergo changes that are not actions proper. But also note that in many cases of apparent passivity or automaticity, for instance, when I’m standing still without paying attention to my doing so, or in Dreyfus’s examples of driving to work, shuffling to a comfortable distance in the lift, or expert athletic performance, there may still be subpersonal processes of active regulation occurring, such as those involved in balancing to ensure that I won't just fall over, preparing one’s body for a rapid return in a tennis match, and so on.
Lastly, when interactions are modulated according to an agent’s goals and needs, and thus have a normative dimension – they are actions, as commonly understood. Within the framework of minimal agency, such normativity arises from the self-producing and self-maintaining nature of the precarious system in question. Through its ongoing individuation, the system intrinsically determines what interactions are supportive of its continued existence, and what interactions threaten its survival. In other words, what is good or bad for a minimal agent, is given by its own organization. When the system is sensitive to these norms, and actively modulates it interactions with respect to them, then we speak of the system adaptively regulating its structural coupling with the environment (Di Paolo 2005). Only such regulations, in contrast to other passive happenings, are acts in the strict sense. They originate in the agent, and they can succeed or fail. Intrinsic normativity of this kind is the third requirement for minimal agency.
In summary, a minimal agent is “an autonomous organization capable of adaptively regulating its coupling with the environment according to the norms established by its own viability conditions” (ibid, p. 376). We argue that the nature of agents as self-asserting systems, able to evaluate external affairs in terms of their own viability, is the origin also of a minimal subjectivity.Footnote 1
However, when we talk about human-level agency, much of our everyday behaviour, while taking place within the constraint of biological viability, is underdetermined by it. Many of our actions, for example, acquire intrinsic value “on top” of their organic functionality: movements can be dexterous, postures awkward, a walk elegant, and so on. The question is whether a new form of autonomy and agency may arise at the behavioural level, not fully determined by biological constraints. Following Di Paolo (2005) and Barandiaran (2007), we suggest that the answer is positive, and that the behavioural analogue to biological agency is a network of precarious but interactively self-sustaining sensorimotor schemes, i.e. a self-asserting sensorimotor repertoire, whose adaptive regulation is directed at the preservation of internal coherence and consistency. Could such a system satisfy the three criteria for minimal agency?
Firstly, non-trivial self-assertion of individuality requires that without the system’s activity its component processes will cease to exist, in other words that they are precarious. How does this apply to sensorimotor organizations? Firstly, many of our behaviours are habitual in nature. By this we do not mean that they are automatic and stereotypical, but that they (and/or the neurodynamic structures underlying them) are reinforced through their repeated exercise, which they also tend to pre-dispose, and without which they are in danger of being extinguished (Barandiaran and Di Paolo 2014; Carlisle 2014). As is well-known, skills and habits tend to decay in the absence of frequent enough enactments, hence their precariousness (see Arthur et al. 2013). A self-reinforcing tendency predisposing future enactments can counteract this decay. But excessive robustness also plays against the precariousness requirement. Instead, as part of a greater network, schemes and habits may also depend on other behaviours as preconditions for their exercise. It is precisely this form of co-dependence that furnishes habits or schemes with a certain plastic opening towards novelty. A habit wears grooves and sets limits to itself. But, according to Dewey (1925), this is true of an isolated habit. Interaction between habits “not only increases the number and variety of habits, but tends to link them subtly together, and eventually to subject habit-forming in a particular case to the habit of recognizing that new modes of association will exact a new use of it. Thus habit is formed in view of possible future changes and does not harden so readily”, (ibid., p. 281). In this way, the sensorimotor agent is individuated as a complex network of interdependent SM schemes, each helping to sustain the others by avoiding both decay and over-rigidity.
Normativity in a network of sensorimotor structures, we propose, arises from the fact that such a network can be coherent and stable to varying degrees. By this we mean that individual sensorimotor structures may be more or less well adapted to the context in which they are usually enacted and that the SM repertoire may hold SM schemes that are, up to a point, mutually conflicting. It is easy to see how in early developmental stages infants may enact the wrong sensorimotor coordinations (see e.g. the dynamical systems analysis of preservative reaching, the A-not-B error, in infants by Smith and Thelen 2003), or possess conflicting sensorimotor schemes (Piaget 1981, relates the story of children’s confusion when first trying to recognise letters that look identical in the mirror and those that do not). Similar perturbations of the repertoire’s coherence are to be expected as the agent matures and acquires new skills (and forgets others) throughout her lifetime.
Finally, when the agent constituted by the sensorimotor network becomes sensitive to these norms of coherence and stability, and adaptively guides transformations that conserve its “viability” (interactional asymmetry), we may speak of a system that exhibits agency at the sensorimotor level. Because such systems have an intrinsic concern for their own stability, and evaluate environmental conditions in terms of what is good or bad for themselves, they entail a subjective perspective (Jonas 1966; Thompson 2007), and therefore allow us to speak of them as possessing interiority and enjoying experiences.Footnote 2
We should clarify at this point that the experiences we propose a sensorimotor agent is able to enjoy differ from the minimal sentience that (mere) organic agency entails. In particular, we claim that sensorimotor agents may experience their actions as their own, and that we can derive the qualities and aspects of how such systems experience their own agency from the way in which they exercise adaptive regulations to maintain a stable sensorimotor repertoire. Piaget has developed exactly such an account of how sensorimotor skills are developed and coherently maintained via adaptive transformations. To this we turn next.
Piaget’s research in the areas of cognitive development and genetic epistemology can be seen as an attempt to determine how higher forms of human understanding (e.g. abstract and rational) arise from earlier and more implicit forms of sensorimotor organization. A fundamental building block in his theory is the concept of a scheme. By this he refers to a kind of behavioural pattern, or action, always required for making (practical) sense of our environment, which matches directly with the level of SMCs we have identified above as “SM schemes”. According to Piaget, and in agreement with the sensorimotor approach, the environment is not a set of pre-existing stimulus conditions that impact on the organism to produce a perceptual or cognitive effect. A subject can rather perceive—in the sense of understanding for what it is, or what it is for—only those environmental aspects or events that she can actively assimilate (integrate or absorb) into already existing sensorimotor schemes. The maturing subject, moreover, faced with an ever changing world (and body), will constantly be challenged by not-yet-assimilated aspects of her environment, which create internal sources of tension and conflict in her cognitive organization. Through adaptive processes of accommodation, Piaget proposes, the existing repertoire of sensorimotor schemes is modulated or transformed over time such as to address new behavioural challenges. The subject is thus continuously poised at the edge between assimilation and accommodation, in a process of equilibration through which she reaches new forms of organizational (meta)stability.
Piaget illustrates the stabilization of a SM scheme as the closure of a cycle of more basic sensorimotor coordinations (which again match with the corresponding level of SMCs defined above). So, for instance, a baby’s scheme for drinking milk from a bottle (and thus her perception of the bottle as affording such action) may involve the more basic coordinations of latching on, suckling, swallowing, breathing etc., organized appropriately such as to achieve the desired result. Individual coordinations, in turn, depend for their correct exercise on the assimilation of corresponding aspects of the environment, such as the shape of the bottle, the sensation of milk flowing or air being inhaled and so on. Such behavioural patterns can be perturbed in different ways. In Piagetian terms, a subject may experience an obstacle when a previously successful sensorimotor coordination fails to assimilate its corresponding environmental aspect (e.g. failure to latch on to the bottle because the teat’s shape has changed). Alternatively, the subject may encounter a lacuna, or gap in the current sensorimotor organization. In this case, something is manifestly unknown about the world since the presumed correct handling of the situation (e.g. latching on) does not lead “as expected” to the next stage in the cycle (e.g. suckling, perhaps because the bottle is empty).
The process of equilibration reduces the occurrence of such perturbations by modifying or deriving new sensorimotor schemes from existing ones, involving processes such as differentiation, grouping, branching, re-ordering, and so on (resulting, for example, in the creation of a bottle-feeding scheme from a prior breast-feeding scheme). Moreover, processes of equilibration also tend to maintain internal coherence in the repertoire of SM schemes. Piaget suggests, for instance, that reciprocal processes of accommodation and assimilation may also occur between schemes, as well as between schemes and the system’s totality (involving a hierarchical dimension of relationships among schemes). Note that the conservation of self-sustaining sensorimotor schemes, and the stability of the SM repertoire as a whole, play the role of adaptive regulations in the definition of minimal agency, and as such may already ground aspects of normativity at the sensorimotor level. What is good or bad for the subject as a sensorimotor agent is, respectively, what can be equilibrated or what provokes tensions or instabilities in his cognitive organization. For an example of how the stability of a SM scheme, rather than some external measure of performance, can guide the learning of a new sensorimotor skill see Kostrubiec et al. (2012).
Piaget’s idea of equilibration can be made more explicit by casting it in terms of processes involving SMCs (Di Paolo et al. 2014). Dynamically, there are two conditions for the successful assimilation of an environmental feature or process into a sensorimotor scheme. The stability condition specifies that the pattern or set of environmental states and the pattern or set of the agent’s states, when engaged in a sensorimotor coordination, are mutually stabilizing. In other words, the fully coupled agent-environment system, when engaged in such a coordination, produces only trajectories that belong to the same functional class (fulfilling the same role in the task). The transition condition specifies that the production of a stable sensorimotor coordination A leads in time to the production of coordination B, where B is the next stage in the sensorimotor scheme comprising the individual coordinations. On this account, Piaget’s lacunae correspond to violations of the transition condition, and obstacles to violations of the stability condition. As we will argue next, these violations may be experienced as breakdowns of agency, and their absence as the feeling of control.