Elisabeth Pacherie, Myrto Mylopoulos and Joshua Shepherd
Affiliation: Institut Jean Nicod, CNRS, EHESS, ENS-PSL, Carleton University & Universitat Autònoma de Barcelona
Category: Philosophy
Keywords: Motor representation, Symbolicity, Analogicity
Date: Thursday 4th of September
Time: 17:00
Location: Gen. Henryk Dąbrowski Hall (006)
View the full session: Format & Vehicle
One of the unifying aims of cognitive science is to understand the etiology, structure and function of mental representations, and how different types of representations interact to produce intelligent thought and action. One important aspect of this project is to develop an account of how mental representations come to have the contents that they do. A second important aspect, which is our focus, is to understand how representations or representational systems encode their contents – to understand how representations are formatted. Much recent work elucidates different types of representational format, and ways that aspects of perception and cognition may be formatted. Our paper targets an underexplored topic: the format of motor representations. Motor representations are relative newcomers in the vast arena of mental representations. For a long period, work on motor production was dominated by the sensory-motor theory of action generation that conceived of actions as reactions to changes in the external environment and as essentially a matter of movements and the muscles that power them. However, centralism, the idea that voluntary actions are largely driven by internal action representations rather than by external events has now become one of the central tenets of contemporary theories of action generation (Jeannerod 2006). In this centralist framework, motor representations are psychological states that function as a bridge between intentions and action production., serve as the primary causal link between an agent’s immediate intention to act and their subsequent behavior. We start by situating motor representations within the context of processes of motor planning and motor control. We then discuss a key distinction between symbolic and analog representational format-types. We take it that the distinction between symbolic and analog representation is best understood as a distinction between format-types, since there may be multiple distinct representational formats that qualify as symbolic or analog. On the symbolic side, for example, one can arguably find representational systems that possess some, but not all, of the six properties Quilty-Dunn et al. (2023) take to characterize the language of thought, namely, discrete constituents, role-filler independence, predicate-argument structure, logical operators, inferential promiscuity, and abstract conceptual content. This sets up ways to taxonomize different types of symbolic formats. Analog representational systems do not share the semantic flexibility of symbolic representational systems such as languages. Why exactly this is the case depends upon one’s account of the mark of analogicity – a controversial issue (Lee et al. 2022, Maley 2023a, Greenberg 2023). Yet, most theorists of analogicity agree that analog representational systems capitalize on the structure of representational vehicles, in that analog representations map this structure to structure in representational content. In our investigation of the format of motor representations, we then take evidence of representations that have compositionality, discrete constituents, role-filler independence, and abstract conceptual content as evidence of a symbolic representational format. Conversely, we take evidence of capitalization on structure – in ways that will depend in part upon details of each case – as evidence of an analog representational format. We first examine a range of empirical evidence showing that motor representations exhibit markers of analogicity. In particular, motor planning seems to capitalize on the structure of aspects of sensory representation, and this structure is reflected in motor behavior. There is also evidence he timing and kinematics of motor representations is specified in a way that involves analogue magnitude representations. We argue that in addition to evidence for analogicity, there is evidence that motor representation bears core markers of symbolic representational format as well. We focus on four such markers: compositionality, discrete constituents, role-filler independence, and abstract conceptual content, marshalling evidence from motor planning, motor control, and motor learning). In particular, we present evidence that the basic structure of motor plans is a means-end structure, where movements are encoded as means towards a certain end or motor outcome, that means-end structure allows for recursivity and hierarchical organization, that both elementary movements and motor chunks can function as discrete, recombinable constituents in motor representation and that motor systems are engaged in structural learning that abstracts from any particular case, and builds abstract structural understanding of the rules for sensory-motor transformations that are most effective across a given task-set. Given that motor representation exhibits both a core marker of analog formatting and core markers of symbolic formatting, we propose that it is best characterized as an interesting form of hybrid representation. In a nutshell, the evidence presented is consistent with a picture of motor representation on which [a] certain parameters of a motor plan are coded (at least partially) analogically, and capitalize on the structure of representational vehicles in various ways, [b] the motor plan itself is constructed and organized utilizing a symbolic scheme, and [c] the parameters that utilize analog formats are embedded within a broader symbolic scheme. We then highlight several open questions this characterization raises. Regarding the rationale for capitalizing on analog structure, the move away from symbolic representational format sacrifices full compositionality and flexibility, but brings certain advantages (e.g., Camp, 2007; Lee et al., 2022). We propose that hybrid formats represent a trade-off between the flexibility of a symbolic format and the efficient encoding of content by analog formats that they can use structure to encode many contents all at once. We further argue that the motor system is also flexible in the sense that motor planning can utilize different strategies to solve a task and either rely on analog or on symbolic representation, depending upon which is most effective. We conclude by noting that this understanding of motor representation as involving a hybrid format where analog contents are embedded within a broader symbolic scheme may impact a range of philosophical debates. This includes the relationship between propositional knowledge and skilled action guidance, the interface problem, which concerns how intentions relate to and interface with motor representations, and the issue of how to draw boundaries between central cognition and the motoric.