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Harvard team fails to retrain planarian worms in 1960s memory study
Wired, reprinting Quanta Magazine, reported that Harvard neuroscientist Sam Gershman's lab could not classically condition planarian flatworms, blocking a bid to retest 1960s claims of cannibal memory transfer.
- New headline Was: “Are Memories Transferable? Meet the Scientists Replicating an Infamous Study to Find Out”
- Our desk filed its story
A Harvard laboratory trying to revive 1960s experiments on memory in planarian flatworms could not get the animals to learn at all, Wired reported Saturday, reprinting a Quanta Magazine account1.
Neuroscientist Sam Gershman and colleagues set out to reproduce classical conditioning used by psychologist James McConnell and student Alan Jacobson, in which worms were shocked while exposed to bright light until they contracted at the light alone1.
McConnell later reported that memories survived beheading and regeneration and that untrained planarians that ate puree of trained worms acquired the response, a claim he tied to RNA1. Wired said other labs reported similar results at the time, then the line of work faded amid failed replications and controversy1.
Gershman and postdoctoral researcher Maddie Snyder followed Jacobson's protocol and posted their results on bioRxiv in April 2026, Wired said: the worms did not scrunch in response to light1. Gershman told Quanta he had expected memory transfer, not basic learning, to be the weak step1.
Research assistant Zachary Kelso collected wild planarians from the Charles River, streams near Eugene, Oregon, and Michigan lakes, including waters McConnell used, Wired said1. Gershman said the group tested about 12 strains and none learned1.
Kelso and Snyder also interviewed Daniel and Reeva Kimble, former McConnell lab members in their nineties, who said the 1960s conditioning had worked1. Snyder said one explanation is inconsistent scoring of worm movements; Gershman called a decades-long biological change in planarians unlikely1.
Wired said memory-transfer experiments in other species have drawn renewed interest, citing David Glanzman's 2018 Aplysia RNA injection work, Coleen Murphy's 2021 C. elegans findings involving the retrotransposon Cer1, and a later Indian Institute of Science preprint on extracellular vesicles1.
Gershman is shifting the project to C. elegans, which has a documented learning literature, Wired reported1.
