Failure to classically condition G. dorotocephala and S. mediterranea flatworms using historical and contemporary light-shock paradigms
- 1Department of Psychology and Center for Brain Science, Harvard University, Cambridge, Massachusetts, United States of America
Abstract
Planarian flatworms represent one of the most evolutionarily informative nervous systems for an account of ancient bilaterian brains. Likewise, the unparalleled regenerative ability of planarians makes possible certain investigations of neural development, memory, and behavior that are simply impossible with other model organisms. Despite these facts, learning and memory are today underexplored in planarians, likely due in part to the controversial legacy of 20th-century experiments on the transfer of memories between individual flatworms. Here, we attempted to replicate and extend the classical conditioning experiments in planarians that were the basis of the later memory transfer work. We failed to find evidence of learning using both historical and contemporary conditioning protocols, and using computer vision methods to avoid subjectivity in manual video annotation. Our results cast doubt on the suitability of historic conditioning protocols for Girardia dorotocephala and Schmidtea mediterranea planarians. We encourage future researchers to explore more ethologically relevant conditioning paradigms to establish a behavioral foundation for investigating the molecular basis of learning.
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BibTeX
@article{kelso2026failure,
title = {{Failure to classically condition G. dorotocephala and S. mediterranea flatworms using historical and contemporary light-shock paradigms}},
author = {Zachary S. Kelso and Madeleine C. Snyder and Samuel J. Gershman},
journal = {PLOS One},
year = {2026},
month = sep,
doi = {10.1371/journal.pone.0358756},
url = {https://doi.org/10.1371/journal.pone.0358756},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Failure to classically condition G. dorotocephala and S. mediterranea flatworms using historical and contemporary light-shock paradigms
AU - Zachary S. Kelso
AU - Madeleine C. Snyder
AU - Samuel J. Gershman
PY - 2026
DA - 2026/09/23
JO - PLOS One
DO - 10.1371/journal.pone.0358756
UR - https://doi.org/10.1371/journal.pone.0358756
AB - Planarian flatworms represent one of the most evolutionarily informative nervous systems for an account of ancient bilaterian brains. Likewise, the unparalleled regenerative ability of planarians makes possible certain investigations of neural development, memory, and behavior that are simply impossible with other model organisms. Despite these facts, learning and memory are today underexplored in planarians, likely due in part to the controversial legacy of 20th-century experiments on the transfer of memories between individual flatworms. Here, we attempted to replicate and extend the classical conditioning experiments in planarians that were the basis of the later memory transfer work. We failed to find evidence of learning using both historical and contemporary conditioning protocols, and using computer vision methods to avoid subjectivity in manual video annotation. Our results cast doubt on the suitability of historic conditioning protocols for Girardia dorotocephala and Schmidtea mediterranea planarians. We encourage future researchers to explore more ethologically relevant conditioning paradigms to establish a behavioral foundation for investigating the molecular basis of learning.
SN - 1932-6203
ER -