Expanding the Reflex Beyond Nervous Systems: animal preparations, tropism, and the presumption of stimulus-response sufficiency – Matthew Sims – Macquarie University

Abstract: Contemporary biologists and philosophers often explain unicellular behaviour in terms of simple stimulus-response mechanisms, even where it appears to involve memory, learning, or context-sensitive evaluation. This talk traces one historical route by which exhaustive explanations in terms of reflex-like behaviour became presumptively available for organisms lacking nervous systems: the animal preparation experiments of eighteenth- and nineteenth-century reflex physiology. I reconstruct an inferential pattern, the animal preparation model (APM), from Whytt and Hall’s decapitated preparations through Loeb’s extension of reflex explanation to cnidarians and non-neuronal organisms. Loeb treated the latter as a secondary comparison class, licensing the conclusion that neuronal structures were dispensable for explaining similar animal behaviour. Jennings’s work on infusoria exposed the presumption underlying this move, yet a residue of the APM’s logic outlived the experimental practice that generated it. I trace this presumption into contemporary treatments of slime mould navigation, where organisms lacking nervous systems continue to attract a standing presumption of reflex sufficiency, one that evidence of flexibility or history-dependence does not by itself defeat. The history of the reflex reveals that stimulus-response explanation is not a neutral methodological starting point, but carries a historical residue that continues to shape explanations of behaviour.

Bio: Matthew Sims is a postdoctoral researcher at Macquarie University, Sydney, Australia, and an affiliate of the Department of History and Philosophy of Science at the University of Cambridge. His research lies at the intersection of the philosophy of biology and the philosophy of cognitive science, with a particular focus on memory and learning, the evolution of cognition, and nineteenth- and early twentieth-century protozoology. He has conducted extensive research on the protist Physarum polycephalum, an acellular slime mould, which was the subject of his first monograph, published by Cambridge University Press.