Hey @user-98789c š I am not aware of studies that have explicitly looked into SoA measurements and pupil diameter but there are some other studies that might be relevant. Below a summary:
Pupil diameter and sense of embodiment: https://escholarship.org/uc/item/8rt963b9#author
Pupil diameter is a proxy of activity of the noradrenergic system and specifically the Locus Coeruleus (LC). There is evidence already from the 80's that when the animals move LC activity increases and pupil dilates. Movement very often has predictable sensory consequences. This might be relevant to your question considering again that the sense of agency is stronger when you generate a stimulus vs. passively perceiving it (imagine hearing your voice when actually producing it vs. hearing your voice from a video - in which case would you feel that you are the agent of what you hear?). There is plenty of work showing increased pupil diameter in "active" movement states. For animal work on that I highly recommend the work done by McGinley lab (e.g., https://pubmed.ncbi.nlm.nih.gov/26074005/ ). For human work, you can check this paper (https://www.sciencedirect.com/science/article/pii/S1053811922007169 ) and part of my own work as well (https://onlinelibrary.wiley.com/doi/10.1111/psyp.14156 and https://www.authorea.com/users/614297/articles/641446-the-multifaceted-nature-of-self-generation-effects-independent-and-interactive-effects-of-actions-predictability-and-delay-on-sensory-processing-and-memory-encoding-of-sounds).
@user-98789c As a last point: There is also evidence in Aston-Jones & Bloom (1981) that the action-induced increase in LC activity might depend on the type of action, differing between goal-directed actions and general active states representing more automatic behaviours such as grooming (they were doing experiments with mice). This might be relevant given that goal-directed actions would be associated with a stronger sense of agency than automatic behaviours like walking, right?
Again, all this work is indirect evidence for sense of agency because they were not explicitly testing that. If you find more papers on agency and pupil diameter, let me know, Iām very much interested in this field.
Thank you so much @nadia this is all very helpful! I'm also currently working on sense of agency and will definitely let you know if I come across any works done with pupil size.