Universal emotions in fact and fiction
Many Minds
Are human emotions universal? Or do they vary from one place to the next and from one time period to the next? It's a big question, an old question. And every discipline that's grappled with it brings is own take, its own framings and forms of evidence. Some researchers appeal to cross-cultural experiments; others turn to neuroimaging studies or conceptual analysis. Some even look to fiction. My guest today is , an Associate Professor of English Literature at Arizona State University. Brad is the author of a new book, ; in it he maps the landscape of debate around this long-contested topic....
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From the archive: Fermentation, fire, and our big brains
Many Minds
Hi friends, We're taking care of some spring cleaning this week. We'll be back in two weeks with a new episode. In the meantime, enjoy this favorite from our archives! - The Many Minds team ––––––––– [originally aired February 22, 2024] Brains are not cheap. It takes a lot of calories to run a brain, and the bigger your brain, the more calories it takes. So how is it that, over the last couple million years, the human brain tripled in size. How could we possibly have afforded that? Where did the extra calories come from? There's no shortage of suggestions out there. Some say...
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Howl, grunt, sing
Many Minds
The tree of life is a noisy place. From one branch come hoots and howls, from another come clicks and buzzes and whines. And coming from all over you hear the swell of song. But what is all this ruckus about? Why do so many animals communicate with sound? What kinds of meaning do these sounds convey? And—beyond the case of human speech—do any of these sounds merit the label of “language”? My guest today is , a zoologist at Cambridge University. Arik is an expert on vocal communication across the animal kingdom and the author of the recent book . Here, Arik and I talk about why the...
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The development of evolution
Many Minds
Evolution is not what it used to be. A lot has changed since Darwin's day. In the first half of the 20th century, evolutionary theory was integrated with an emerging understanding of genetics. Late in the 20th century, biologists started taking seriously the idea that organisms don't just adapt to their environments, they change them. Recently, researchers have started to acknowledge the role of culture in evolutionary processes. And so slowly our understanding of evolution has been reconsidered, updated, expanded. And more updates are underway. But it's not just our understanding of evolution...
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String theories
Many Minds
Where would our species be without string? It's one of our most basic technologies—so basic that it's easy to overlook. But humans have used string—and its cousins rope, yarn, cordage, thread, etc.—for all kinds of purposes, stretching back tens of thousands of years. We've used it for knots and textiles and fishing nets and carrier bags and bow-strings and record-keeping devices. It's one of the most ubiquitous, flexible, and useful technologies we have. But we haven't only put string to practical purposes. We've also long used it to tickle our minds. My guest today is . Roope is a...
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The other half of the brain
Many Minds
Neurons have long enjoyed a kind of rock star status. We think of them as the most fundamental units of the brain—the active cells at the heart of brain function and, ultimately, at the heart of behavior, learning, and more. But neurons are only part of the story—about half the story, it turns out. The other half of the brain is made up of cells called glia. Glia were long thought to be important structurally but not particularly exciting—basically stage-hands there to support the work of the neurons. But in recent decades, at least among neuroscientists, that view has faded. In our...
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A paradox of learning
Many Minds
How do we learn? Usually from experience, of course. Maybe we visit some new place, or encounter a new tool or trick. Or perhaps we learn from someone else—from a teacher or friend or YouTube star who relays some shiny new fact or explanation. These are the kinds of experiences you probably first think of when you think of learning. But we can also learn in another way: simply by thinking. Sometimes we can just set our minds to work—just let the ideas already in our heads tumble around and spark off each other—and, as if by magic, come away with a new understanding of the world. But how...
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From the archive: The octopus and the android
Many Minds
Happy holidays, friends! We will be back with a new episode in January 2025. In the meantime, enjoy this favorite from our archives! ----- [originally aired Jun 14, 2023] Have you heard of Octopolis? It’s a site off the coast of Australia where octopuses come together. It’s been described as a kind of underwater "settlement" or "city." Now, smart as octopuses are, they are not really known for being particularly sociable. But it seems that, given the right conditions, they can shift in that direction. So it's not a huge leap to wonder whether these kinds of cephalopod congregations could...
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Your brain on language
Many Minds
Using language is a complex business. Let's say you want to understand a sentence. You first need to parse a sequence of sounds—if the sentence is spoken—or images—if it's signed or written. You need to figure out the meanings of the individual words and then you need to put those meanings together to form a bigger whole. Of course, you also need to think about the larger context—the conversation, the person you're talking to, the kind of situation you're in. So how does the brain do all of this? Is there just one neural system that deals with language or several? Do different...
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Nestcraft
Many Minds
How do birds build their nests? By instinct, of course—at least that's what the conventional wisdom tells us. A swallow builds a swallow's nest; a robin builds a robin's nest. Every bird just follows the rigid template set down in its genes. But over the course of the last couple of decades, scientists have begun to take a closer look at nests—they've weighed and measured them, they've filmed the building process. And the conventional wisdom just doesn't hold up. These structures vary in all kinds of ways, even within a species. They're shaped by experience, by learning, by cultural...
info_outlineWhere 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!
A transcript of this episode is available here.
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 Templeton World Charity Foundation to UCLA. It 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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