Clarifying the contribution of motor simulation to speech perception and action recognition
(2025)
Files
THESE_FINAL_IMPRESSION.pdf
Embargo Access until 2026-12-31 - Adobe PDF
- 2.51 MB
Details
- Authors
- Supervisors
- Vannuscorps, Gilles
- Abstract
- Many experiences in daily life that we take for granted pose surprisingly challenging scientific questions. One question concerns how we understand others so easily and effortlessly—whether we are listening to them or watching them move. This thesis examines the contribution of a single mechanism to these abilities: motor simulation. For several decades, motor simulation—namely, the covert simulation in the listener’s or observer’s brain of the heard speech or observed action—has been proposed as a key mechanism supporting speech perception and action recognition. Some authors have even argued that it is necessary, allowing sensory input to be directly mapped onto the observer’s own motor representations used to speak or to move, thereby enabling effortless recognition. These proposals have motivated a large body of research aiming to determine the extent of motor simulation’s contribution. However, the lack of research targeting the specific contexts in which motor simulation might play a role has not only hindered the emergence of a clear understanding of its functional contribution, but has also fueled ongoing debates between proponents and skeptics. This thesis builds on theoretical accounts suggesting that the involvement of motor simulation is context-dependent and may be recruited primarily under “adverse” conditions. These conditions occur when sensory input is too ambiguous or unfamiliar to be rapidly matched to stored representations for recognition—for example, when speech sounds are presented in noise, when actions are shown as point-light displays, or when facial expressions are subtle, morphed, or otherwise non-prototypical. Guided by this framework, the thesis set out to address specific, well-defined questions in two domains—speech perception and action recognition—to clarify the functional contribution of motor simulation. Chapter 2 focused on behavioral studies commonly cited as evidence for motor simulation contribution to speech perception. While these findings are often consistent with a motor simulation account, they can also be explained by alternative hypotheses. To address this issue, the present work set out to disentangle the competing explanations. The results supported one such alternative, leaving open the question of whether motor simulation functionally contributes to speech perception. Chapters 3 and 4 tested a popular hypothesis that motor simulation is necessary for effortless action recognition. Using a single-case approach involving individuals with congenital facial paralysis, these studies presented prototypical facial movements under clear visual conditions. As a proof of concept, the findings demonstrated that lip-reading and facial expressions can be recognized even without motor simulation, challenging the claim that it is the sole mechanism enabling effortless recognition. Finally, Chapter 5 examined a key prediction derived from context-dependent hypotheses: that motor simulation supports recognition when actions cannot be matched rapidly and easily with stored representations in visual memory (such as in adverse conditions). Testing both individuals with facial paralysis and typically developed controls, the results showed that under visually adverse conditions, recognition performance declined when motor simulation was absent or disrupted—supporting the idea that motor simulation acts as a compensatory mechanism in these specific circumstances. Overall, this thesis underscores the value of precise, hypothesis-driven methods to advance our understanding of motor simulation’s contribution to speech perception and action recognition.
- Affiliations
Citations
Carneiro, S. (2025). Clarifying the contribution of motor simulation to speech perception and action recognition.