In the 1960s, behavioral psychologist James McConnell claimed that planarian worms could be classically conditioned and that their memories could be transferred to other worms through cannibalism. His experiments, though sensational, were inconsistent and eventually dismissed. Now, over 60 years later, Harvard neuroscientist Sam Gershman and his team are attempting to replicate those experiments — but they can’t get the worms to learn at all. Despite using the same protocols, sourcing worms from the same locations, and consulting original researchers, modern planarians show no signs of conditioning. This raises questions about whether past results were influenced by observer bias or if environmental or genetic changes have altered the worms themselves. While planarian memory remains unproven, newer studies in sea slugs and C. elegans suggest RNA-based memory transfer may be possible in other species.