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 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, is if by magic, come away with a new understanding of the world. But...
info_outline
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...
info_outline
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...
info_outline
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_outline
Animal, heal thyself
Many Minds
What happens to animals when they get sick? If they’re pets or livestock, we probably call the vet. And the vet may give them drugs or perform a procedure. But what about wild animals? Do they just languish in misery? Well, not so much. It turns out that animals—from bees to butterflies, porcupines to primates—medicate themselves. They seek out bitter plants, they treat wounds, they amputate limbs, they eat clay—the list goes on. This all raises an obvious question: How do they know to do this? How do they know what they know about healing and medicine? It also invites a related...
info_outline
The rise of machine culture
Many Minds
The machines are coming. Scratch that—they're already here: AIs that propose new combinations of ideas; chatbots that help us summarize texts or write code; algorithms that tell us who to friend or follow, what to watch or read. For a while the reach of intelligent machines may have seemed somewhat limited. But not anymore—or, at least, not for much longer. The presence of AI is growing, accelerating, and, for better or worse, human culture may never be the same. My guest today is . Iyad directs the at the Max Planck Institute for Human Development in Berlin. Iyad is a...
info_outline
How should we think about IQ?
Many Minds
IQ is, to say the least, a fraught concept. Psychologists have studied IQ—or g for “general cognitive ability”—maybe more than any other psychological construct. And they’ve learned some interesting things about it. That it's remarkably stable over the lifespan. That it really is general: people who ace one test of intellectual ability tend to ace others. And that IQs have risen markedly over the last century. At the same time, IQ seems to be met with increasing squeamishness, if not outright disdain, in many circles. It's often seen as crude, misguided, reductive—maybe a whole lot...
info_outline
Rethinking the "wood wide web"
Many Minds
Forests have always been magical places. But in the last couple decades, they seem to have gotten a little more magical. We've learned that trees are connected to each other through a vast underground network—an internet of roots and fungi often called the "wood wide web". We've learned that, through this network, trees share resources with each other. And we've learned that so-called mother trees look out for their own offspring, preferentially sharing resources with them. There's no question that this is all utterly fascinating. But what if it's also partly a fantasy? My guest today is ....
info_outline
Electric ecology
Many Minds
There's a bit of a buzz out there, right now, but maybe you haven’t noticed. It's in the water, it's in the air. It's electricity—and it's all around us, all the time, including in some places you might not have expected to find it. We humans, after all, are not super tuned in to this layer of reality. But many other creatures are—and scientists are starting to take note. My guest today is . Sam is a sensory ecologist at the Natural History Museum in Berlin, and one of a handful of scientists uncovering some shocking things about the role of electricity in the natural world. Here, Sam...
info_outline
The nature of nurture
Many Minds
The idea of a "maternal instinct"—the notion that mothers are wired for nurturing and care—is a familiar one in our culture. And it has a flipside, a corollary—what you might call “paternal aloofness.” It's the idea that men just aren't meant to care for babies, that we have more, you know, manly things to do. But when you actually look at the biology of caretaking, the truth is more complicated and much more interesting. My guest today is . She is Professor Emerita of Anthropology at the University of California, Davis and the author of the new book, . In it, she examines...
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.
Subscribe to Many Minds on Apple, Stitcher, Spotify, Pocket Casts, Google Play, or wherever you listen to podcasts. You can also now subscribe to the Many Minds newsletter here!
We welcome your comments, questions, and suggestions. Feel free to email us at: [email protected].
For updates about the show, visit our website or follow us on Twitter: @ManyMindsPod.