Towards a common framework of grounded action cognition: Relating motor control, perception and cognition.

The relation between motor control and action cognition - including action-related thoughts and action-related perception - has been subject to controversial discussions in the last three decades. During these decades, cognitive neuroscience has been increasingly confronted with a huge variety of different accounts trying to understand and explain the relation between these systems, their interdependencies and the mediating mechanisms by establishing notions such as "internal models", "simulation" or "shared representation". These accounts, however, include a large array of partly overlapping, partly contradictory theories using similar terms for different mechanisms and different terms for similar mechanisms. In the absence of a systematic work-up and comparison, this array of accounts and theories leads to confusion in the field, duplication of experimental work, and unconnected parallelism of theory formation within and between different disciplines. Here we provide a systematic comparison of current models and prospective theories that deal with the relation between cognition, perception and motor control mechanisms. In a second step, we propose "grounded action cognition" as a comprehensive metatheoretical framework which defines different hypothetical possibilities of the relations between these domains, offers systematic insights into current models and theories and last but not least may help to increase comparability of empirical research in the domain of action and action cognition.

The experience of agency: an interplay between prediction and postdiction.

The experience of agency, i.e., the registration that I am the initiator of my actions, is a basic and constant underpinning of our interaction with the world. Whereas several accounts have underlined predictive processes as the central mechanism (e.g., the comparator model by C. Frith), others emphasized postdictive inferences (e.g., post-hoc inference account by D. Wegner). Based on increasing evidence that both predictive and postdictive processes contribute to the experience of agency, we here present a unifying but at the same time parsimonious approach that reconciles these accounts: predictive and postdictive processes are both integrated by the brain according to the principles of optimal cue integration. According to this framework, predictive and postdictive processes each serve as authorship cues that are continuously integrated and weighted depending on their availability and reliability in a given situation. Both sensorimotor and cognitive signals can serve as predictive cues (e.g., internal predictions based on an efferency copy of the motor command or cognitive anticipations based on priming). Similarly, other sensorimotor and cognitive cues can each serve as post-hoc cues (e.g., visual feedback of the action or the affective valence of the action outcome). Integration and weighting of these cues might not only differ between contexts and individuals, but also between different subject and disease groups. For example, schizophrenia patients with delusions of influence seem to rely less on (probably imprecise) predictive motor signals of the action and more on post-hoc action cues like e.g., visual feedback and, possibly, the affective valence of the action outcome. Thus, the framework of optimal cue integration offers a promising approach that directly stimulates a wide range of experimentally testable hypotheses on agency processing in different subject groups.

Memory and content.

The paper argues that any theory of content has to adopt a "functionalistic core" to concord with the cognitive sciences. This functionalistic core requires that representations are defined as substitutes in functions that describe the flexible behavior to be explained by the representation. The content of a representation can thus only be determined if the representation is "in use", i.e. if it is an argument in such a function. The stored entities in memory are not in use while they are stored, and hence cannot be assigned a specific content. The term "template" is introduced to describe stored entities in memory. The discussion of some implications of this result show that some deep philosophical problems follow from this argument as well as consequences for empirical research on memory.

Me or not me--an optimal integration of agency cues?

Recent work has demonstrated that the sense of agency is not only determined by efference-copy-based internal predictions and internal comparator mechanisms, but by a large variety of different internal and external cues. The study by Moore and colleagues [Moore, J. W., Wegner, D. M., & Haggard, P. (2009). Modulating the sense of agency with external cues. Conscious and Cognition] aimed to provide further evidence for this view by demonstrating that external agency cues might outweigh or even substitute efferent signals to install a basic registration of self-agency. Although the study contains some critical points that, so we argue, are central to a proper interpretation of the data, it hints at a new perspective on agency: optimal cue integration seems to be the key to a robust sense of agency. We here argue that this framework could allow integrating the findings of Moore and colleagues and other recent agency studies into a comprehensive picture of the sense of agency and its pathological disruptions.

I move, therefore I am: a new theoretical framework to investigate agency and ownership.

The neurocognitive structure of the acting self has recently been widely studied, yet is still perplexing and remains an often confounded issue in cognitive neuroscience, psychopathology and philosophy. We provide a new systematic account of two of its main features, the sense of agency and the sense of ownership, demonstrating that although both features appear as phenomenally uniform, they each in fact are complex crossmodal phenomena of largely heterogeneous functional and (self-)representational levels. These levels can be arranged within a gradually evolving, onto- and phylogenetically plausible framework which proceeds from basic non-conceptual sensorimotor processes to more complex conceptual and meta-representational processes of agency and ownership, respectively. In particular, three fundamental levels of agency and ownership processing have to be distinguished: The level of feeling, thinking and social interaction. This naturalistic account will not only allow to "ground the self in action", but also provide an empirically testable taxonomy for cognitive neuroscience and a new tool for disentangling agency and ownership disturbances in psychopathology (e.g. alien hand, anarchic hand, anosognosia for one's own hemiparesis).

Beyond the comparator model: a multifactorial two-step account of agency.

There is an increasing amount of empirical work investigating the sense of agency, i.e. the registration that we are the initiators of our own actions. Many studies try to relate the sense of agency to an internal feed-forward mechanism, called the "comparator model". In this paper, we draw a sharp distinction between a non-conceptual level of feeling of agency and a conceptual level of judgement of agency. By analyzing recent empirical studies, we show that the comparator model is not able to explain either. Rather, we argue for a two-step account: a multifactorial weighting process of different agency indicators accounts for the feeling of agency, which is, in a second step, further processed by conceptual modules to form an attribution judgement. This new framework is then applied to disruptions of agency in schizophrenia, for which the comparator model also fails. Two further extensions are discussed: We show that the comparator model can neither be extended to account for the sense of ownership (which also has to be differentiated into a feeling and a judgement of ownership) nor for the sense of agency for thoughts. Our framework, however, is able to provide a unified account for the sense of agency for both actions and thoughts.