From the archive: Philosophers on psychedelics
Many Minds
Hi friends! We're taking a bit of a summer pause. We will be back soon—in the meanwhile, enjoy this listener favorite from our archives! ----- [originally aired May 14, 2025] Some call it the "psychedelic renaissance." In the last decade or so, interest in psychedelic drugs has surged—and not just among Silicon Valley types and psychiatrists and neuroscientists. It's also surged among a stereotypically soberer crowd: academic philosophers. The reasons are clear. With their varied and sometimes transformative effects, psychedelics raise ethical questions, epistemological questions,...
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The origins of Darwin's ideas
Many Minds
No discipline, no sphere of intellectual life, has been untouched by the work of Charles Darwin. He died in 1882 but his ideas are very much alive; they're now central to how we understand the natural world, the human mind, non-human minds, plants, biogeography, morality and emotion, culture, language, and more. But where did his ideas come from? How did they grow out of his travels, his social circle, his hobbies, his particular cast of mind? My guest today is . Janet is Professor Emerita at Harvard University in the department of the History of Science. She is perhaps best known for...
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The sparkling deep
Many Minds
It’s tempting to see bioluminescence as an oddity, one of those rare eccentricities of life on earth. And, on land, maybe that’s true. But our planet is mostly water, and out in the open ocean bioluminescence is utterly commonplace. Creatures of all shapes and sorts sparkle and glow, glitter and pulse. But what are these displays for? Why did they evolve? How did light become the currency of the deep? My guest today is . Sönke is a Distinguished Professor of Biology at Duke University, where he and his research group study the visual ecology of the ocean. He’s the author of...
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Is Man the Hunter just a myth?
Many Minds
There's a story about of our past that you know well. It goes like this: At some point earlier in human evolution, we started to hunt. Men in particular—perhaps channeling some deep-seated aggressive impulses—began to seek out big game. This new food source, this bonanza of calories, was what allowed our brains to expand. It changed our bodies and our societies and sent our species off on a whole new track. In short, Man the Hunter made us human. This story—told in different versions, with different points of emphasis—has circulated for decades. It's been debunked and revived, rejected...
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Babies, dogs, and the riddles of word learning
Many Minds
It's kind of astonishing, really, that kids ever learn words. Each one poses a little riddle. Does this sound string refer to a person? A category of things? Or maybe some other feature of the blooming, buzzing world? And yet word learning happens. In fact, we now know it begins earlier in infancy than we realized. And we now know, further, that dogs (or at least some dogs) understand words as well. So how does this happen? What do babies and dogs really know about words? And how might we go about figuring this all out? My guests today are and Dr. Claudia Fugazza. Elika is an Associate...
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The inner life of the hand
Many Minds
Newton saw in the human hand proof of the divine; Darwin saw a key to our species' success. Many others, too, have described the hand in hyperbolic terms, as a paragon of design, a cornerstone of human uniqueness, an engine of our achievements. But what makes the human hand so powerful? Is it the proportions of the fingers? Is it the opposability of the thumb? Or, could it be none of this? Could it be that the real power of our hands lies—not in the physical design—but elsewhere, out of sight? My guest today is . Matt is Professor of Cognitive Neuroscience at Birkbeck, University of...
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From the archive: The cuttlefish and its coat of many colors
Many Minds
Hi friends! We're skipping a beat to take care of some spring housekeeping tasks. We will be back in May! In the meanwhile, enjoy this listener favorite from our archives! ----- [originally aired April 30, 2025] We humans have a hard time becoming invisible. For better or worse, we're basically stuck with the skin and body we have; we’re pretty fixed in our color, our shape, our overall appearance. And so we're fascinated by creatures that aren't—creatures that morph to meet the moment, that can functionally disappear, that can shape-shift on a dime. And no creatures are more skilled,...
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Illuminating cave art
Many Minds
Deep in our past, in the dark depths of caves, our ancestors did something strange and beautiful. Working by firelight, some doodled little designs. Others made hand stencils. Some saw a bulge of rock, or a crack in the wall, and thought to turn it into a horse or a bison. Why did they make this art? What did it mean to them? Who were these artists? These questions are old—very old—but thanks to new methods and new interpretive frameworks, archaeologists are beginning to see them in a new light. My guest today is . Izzy is an archaeologist at Aarhus University in Denmark,...
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What can AI teach us about the mind?
Many Minds
Everyone is talking about AI these days. Often these conversations are about how AI might upend education, or work, or social life, or maybe civilization itself. But among cognitive scientists and psychologists the conversation inevitably drifts toward other questions. What does this latest generation of AI tell us about the human mind? Is it putting old ideas and theories to rest? Is it ushering in new ones? Will AI—in other words—also upend cognitive science? My guests today are and . Mike is a Professor of Psychology at Stanford University, where focuses on language learning and...
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Mutualisms all the way down
Many Minds
No one is an island. We all depend on each other in critical, often tangled ways. And when I say "we" and "each other" I don't just mean humans. Yes, we humans rely on other humans. But we also rely on bees, yeasts, dogs, bacteria, and countless other creatures big and small. These interspecies dependencies—or mutualisms, as biologists call them—have deflected and inflected our history. And there's no doubt they will also inflect our future. My guest today is . Rob is Professor of Applied Ecology at North Carolina State University, where he studies the creatures and ecologies all...
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We're taking a much-needed August pause—we'll have new episodes for you in September. In the meanwhile, enjoy this pick from our archives!
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[originally aired February 8, 2024]
Where do memories live in the brain? If you've ever taken a neuroscience class, you probably learned that they're stored in our synapses, in the connections between our neurons. The basic idea is that, whenever we have an experience, the neurons involved fire together in time, and the synaptic connections between them get stronger. In this way, our memories for those experiences become minutely etched into our brains. This is what might be called the synaptic view of memory—it's the story you'll find in textbooks, and it's often treated as settled fact. But some reject this account entirely. The real storehouses of memory, they argue, lie elsewhere.
My guest today is Dr. Sam Gershman. Sam is Professor of Psychology at Harvard University, and the director of the Computational Cognitive Neuroscience Lab there. In a recent paper, he marshals a wide-ranging critique of the synaptic view. He makes a compelling case that synapses can't be the whole story—that we also have to look inside the neurons themselves.
Here, Sam and I first discuss the synaptic view and the evidence that seems to support it. We then talk about some of the problems with this classic picture. We consider, for example, cases where memories survive the radical destruction of synapses; and, more provocatively, cases where memories are formed in single-celled organisms that lack synapses altogether. We talk about the dissenting view, long lurking in the margins, that intracellular molecules like RNA could be the real storage sites of memory. Finally, we talk about Sam's new account—a synthesis that posits a role for both synapses and molecules. Along the way we touch on planaria and paramecia; spike-timing dependent plasticity; the patient H.M.; metamorphosis, hibernation, and memory transfer; the pioneering work of Beatrice Gelber; unfairly maligned ideas; and much, much more.
Before we get to it, one important announcement: Applications are now open for the 2024 Diverse Intelligences Summer Institute (or DISI)! The event will be held in beautiful, seaside St Andrews, Scotland, from June 30 to July 20. If you like this show—if you like the conversations we have and the questions we ask—it's a safe bet that you'd like DISI. You can find more info at disi.org—that's disi.org. Review of applications will begin on Mar 1, so don't delay.
Alright friends, on to my conversation about the biological basis of memory with Dr. Sam Gershman. Enjoy!
Notes and links
4:00 - A general audience article on planarian memory transfer experiments and the scientist who conducted them, James V. McConnell.
8:00 - For more on Dr. Gershman’s research and general approach, see his recent book and the publications on his lab website.
9:30 - A brief video explaining long-term potentiation. An overview of “Hebbian Learning.” The phrase “neurons that fire together wire together” was, contrary to widespread misattribution, coined by Dr. Carla Shatz here.
12:30 - The webpage of Dr. Jeremy Gunawardena, Associate Professor of Systems Biology at Harvard University. A recent paper from Dr. Gunawardena’s lab on the avoidance behaviors exhibited by the single-celled organism Stentor (which vindicates some disputed, century-old findings).
14:00 - A recent paper by C. R. Gallistel describing some of his views on the biological basis of memory.
19:00 - The term “engram” refers to the physical trace of a memory. See recent reviews about the so-called search for the engram here, here, and here.
20:00 - An article on the importance of H.M. in neuroscience.
28:00 - A review about the phenomenon of spike-timing dependent plasticity.
33:00 - An article, co-authored by former guest Dr. Michael Levin, on the evidence for memory persistence despite radical remodeling of brain structures. See our episode with Dr. Levin here.
35:00 - A study reporting the persistence of memories in decapitated planarians. A popular article about these findings.
36:30 - An article reviewing one chapter in the memory transfer history. Another article reviewing evidence for “vertical” memory transfer (between generations).
39:00 - For more recent demonstrations of memory transfer, see here and here.
40:00 - A paper by Dr. Gershman, Dr. Gunawardena, and colleagues reconsidering the evidence for learning in single cells and describing the contributions of Dr. Beatrice Gelber. A general audience article about Gelber following the publication of the paper by Dr. Gershman and colleagues.
45:00 – A recent article arguing for the need to understand computation in single-celled organisms to understand how computation evolved more generally.
46:30 – Another study of classical conditioning in paramecia, led by Dr. Todd Hennessey.
49:00 – For more on plant signaling, see our recent episode with Dr. Paco Calvo and Dr. Natalie Lawrence.
56:00 – A recent article on “serial reversal learning” and its neuroscientific basis.
1:07:00 – A 2010 paper demonstrating a role for methylation in memory.
Recommendations
The Behavior of the Lower Organisms, by Herbert Spencer Jennings
Memory and the Computational Brain, by C. R. Gallistel and Adam Philip King
Wetware, by Dennis Bray
Many Minds is a project of the Diverse Intelligences Summer Institute, which is made possible by a generous grant from the John Templeton Foundation to Indiana University. The show is hosted and produced by Kensy Cooperrider, with help from Assistant Producer Urte Laukaityte and with creative support from DISI Directors Erica Cartmill and Jacob Foster. Our artwork is by Ben Oldroyd. Our transcripts are created by Sarah Dopierala.
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