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, metaphysical questions, questions about the nature of experience and the nature of the mind.
My guest today is Dr. Chris Letheby. Chris is a philosopher of cognitive science at the University of Western Australia and the author of the 2021 book, Philosophy of Psychedelics.
Here, Chris and I talk about the so-called classic psychedelics—LSD, psilocybin, ayahuasca, and others—and how interest in them has gone through three distinct waves. We discuss the effects that these substances seem to have, in particular their capacity to treat certain psychiatric conditions and their tendency to induce "mystical-like" experiences. We consider the idea that psychedelics might serve as agents of moral enhancement. And we dig into the psychological and neural mechanisms by which psychedelics seem to have their diverse—and often salutary—effects. Along the way, we talk about ontological shock, comforting delusions, brain plasticity, unselfing, microdosing, placebo effects and adverse effects, physicalism and idealism, the REBUS model, environmental virtues, plant consciousness, meditation, and much more.
Maybe this is obvious but this episode is not just for the seasoned psychonauts out there. Whatever your personal experience with these substances, they offer a distinctive window into the mind—a new way of grappling with big questions. Perhaps this much is also obvious but we're not encouraging or endorsing the use of psychedelics here—just offering a little fuel for your intellectual fires!
Alright friends, on to my conversation w/ Dr. Chris Letheby. Enjoy!
 
A transcript of this episode is available here. 
 
Notes and links
4:00 – For a brief historical overview of research into psychedelics, see this paper.
8:30 – For work by an early trailblazer in the philosophy of psychedelics, see Thomas Metzinger's Being No One.
12:30 – For our earlier episode on the psychology and philosophy of visual illusions, see here. 
18:00 – For a history of the concept of "set and setting," see here.
19:00 – A 2024 review of "adverse events" in classic psychedelics.
26:00 – A blog post on the history of the term "psychedelic."
27:00 – A recent review and meta-analysis of the use of psychedelic therapy for depressive symptoms.
31:00 – On mystical experience see Walter Stace's classic work, Mysticism and Philosophy. On the measurement of mystical-type experiences, see, e.g., Walter Pahnke's paper here.
36:00 – On the idea of "psychoplastogens," see here.
39:00 – See our earlier audio essay on placebo effects.
41:00 – For the study using Ritalin as an active placebo, see here. 
44:00 – Michael Pollan's book on psychedelics is here.
48:00 – On the idea of "idealism," see here.
50:30 – For the 2021 study on psychedelics' capacity to alter metaphysical beliefs, see here.
54:00 – For Dr. Letheby and collaborators' paper about the "mysticism wars," see here.
1:02:00 – For a popular article on the possibility that psychedelics reduce fear of death, see here.
1:03:00 – For Dr. Letheby's paper on psychedelics and the fear of death, see here.
1:11:00 – The phrase "comforting delusion" comes from an article by Michael Pollan.
1:15:00 – For the "REBUS model," see here.
1:20:00 – On the idea that psychedelics could serve as agents of moral enhancement, see the paper by Brian Earp here.
1:21:00 – For Dr. Letheby's paper on psychedelics and environmental virtues, see here. For his paper on psychedelics and forgiveness, see here.
1:23:00 – On the subfield of "virtue ethics," see here. On the virtue of "living in place," see the paper by Nin Kirkham here.
1:28:00 – For the New Yorker article, by Matthew Hutson, on how psychedelics led him to see trees as smart, see here. For the study, led by Sandeep Nayak, on psychedelics leading people to expand their attributions of consciousness, see here.
1:32:00 – For a first paper by Dr. Letheby on the comparison between meditation and psychedelics, see here.
 
Recommendations
Psychedelic Experience, Aidan Lyon
Varieties of Psychedelic Experience, Robert Masters & Jean Houston
The Antipodes of the Mind, Benny Shanon
 
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.
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: manymindspodcast@gmail.com. 
For updates about the show, visit our website or follow us on Twitter (@ManyMindsPod) or Bluesky (@manymindspod.bsky.social).

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 Dr. Janet Browne. Janet is Professor Emerita at Harvard University in the department of the History of Science. She is perhaps best known for her widely acclaimed two-volume biography of Charles Darwin. And she has now published an updated and abridged single-volume version.  
Here, Janet and I talk about Darwin's life and ideas. We pick up the story during his travels on the Beagle, a five-year voyage that laid the foundation for the rest of his career. We talk about what he was reading, what he was seeing, and how these experiences helped form his most influential work, On the Origin of Species. We discuss Darwin's style as a thinker, as a naturalist, as a writer, and as an experimentalist. We touch on his relationships with contemporaries like Charles Lyell and Alfred Russel Wallace. And we consider his long—and often overlooked—engagements with pigeons, barnacles, plants, and worms. 
I greatly enjoyed Janet's two-volume biography of Darwin, and I enjoyed this new single-volume edition just as much. So if this episode sparks your interest, I heartily recommend that you check these books out.
Alright friends, on to my conversation with Dr. Janet Browne. Enjoy!
 
Notes
3:30 – Darwin's autobiography is available here. All of Darwin's letters are readable (and searchable) at the Darwin Correspondence Project.
11:00 – Darwin's account of his five-year stint on the HMS Beagle can be found in his book, The Voyage of the Beagle. 
17:00 – Charles Lyell's Principles of Geology (Vol. 1).
27:00 – For a recently published history of Lamarck and his ideas, see here. 
31:00 – For more on Darwin's interest in pigeons and pigeon breeding, see here. 
34:00 – For more on Darwin's barnacle studies, see here.
40:00 – For a brief account of the relationship between Wallace and Darwin, see Dr. Browne's article here.
44:00 – Alfred Russel Wallace's The Malay Archipelago is here. Wallace's own essay on natural selection, sent to Darwin before the publication of On the Origin of Species, is here. The proceedings in which Darwin's and Wallace's first papers on natural selection appeared together.
53:00 – For a modern treatment of the concept of sexual selection, see here. For an online version of Darwin's The Descent of Man, see here. For a recent collection of essays on Darwin's Descent, including one by Dr. Browne, see here. 
58:00 – Darwin's The Expression of the Emotions in Man and Animals. 
1:03:00 – Darwin's short article, 'A biographical sketch of an infant.'
1:08:00 – Darwin's The Power of Movement in Plants. For more about Darwin's last book, The Formation of Vegetable Mould, through the Action of Worms, see here. For more about Darwin's "root-brain hypothesis," see our earlier episode.
1:14:00 – For more on Darwin's theory of gemmules and pangenesis, see here.
1:15:00 – For more on Darwin's substantial archive, see here. 
 
Recommendations
Darwin and the Barnacle, Rebecca Stott
Natural Magic, Renée Bergland

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 Dr. Sönke Johnsen. 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 a number of books: most recently Into the Great Wide Ocean, about life in the pelagic realm, and The Radiant Sea, a photographic tour of bioluminescence and color, written in collaboration with Dr. Steven Haddock. 
Here, Sönke and I talk about the open ocean: the most common habitat on our planet, yet one that many people will never experience. We consider the curious distribution of bioluminescence— rare on land, exceptionally prevalent in the ocean, and all but absent in freshwater. We talk about how bioluminescence seems to have evolved—many, many times over in fact. We survey the functions of making light in the deep—from counter-illumination to courtship to revenge. Finally, we consider what Sönke takes to be the biggest remaining puzzle about bioluminescence at sea. 
Alright friends, if you're enjoying Many Minds, we ask (humbly) if you would think about rating us, reviewing us, leaving us a comment, boosting us on social media, or perhaps haranguing your friends—relentlessly—until they give us a listen. 
Without further ado, onto my conversation with Dr. Sönke Johnsen. Enjoy! 
 
Notes
3:30 – The scientific report by Dr. Johnsen and colleagues describing the bioluminescent octopus, Stauroteuthis syrtensis.  
12:00 – A popular article on the bristlemouth. The article reports a scientist's estimate of "as many as a dozen [bristlemouths] per square meter of ocean."
15:00 – A recent discussion of the "burglar alarm hypothesis." 
18:00 – The website for the Johnsen Lab at Duke University. 
24:00 – A chart and discussion of the depth zones of the ocean.
29:30 – A study by Séverine Martini and Steven Haddock quantifying the prevalence of bioluminescence at different depths. A popular write-up of the same study. 
33:00 – A popular article on vertical migration in the ocean, also called "diel vertical migration." A recent scientific study of the phenomenon. 
39:00 – A recent article on the evolution of bioluminescence. 
45:00 – For detailed scientific discussion of the physical basis of bioluminescence, fluorescence, and other phenomena we discuss, see Dr. Johnson's book, The Optics of Life.  
52:00 – For previous episodes on the use of sound in the animal kingdom, see here and here. For our previous episode on electroreception and electric ecology (including in marine organisms), see here.  
57:00 – For more on the functions of bioluminescence, see here. For a report of a recently discovered function of bioluminescence, see here. 
1:03:00 – An article by Dr. Johnsen about the different colors of bioluminescence present in the deep sea.
1:05:00 – A video of ostracod mating displays.  
1:08:00 – For our recent episode on cave art, see here.
1:16:00 – For our earlier episode on firefly synchronization, see here.  
 
Recommendations
Website and review article by Steven Haddock
The lab of Todd Oakley
Below the edge of darkness, Edie Widder
 
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.
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: manymindspodcast@gmail.com.
For updates about the show, visit our website or follow us on Bluesky (@manymindspod.bsky.social).

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 and reimagined. What is the history behind the Man the Hunter idea? How does it square with our current understandings of evolution? Is it, in fact, pure fiction?
My guest today is Dr. Vivek Venkataraman. Vivek is an evolutionary anthropologist at the University of Calgary, and an editor-in-chief of the journal Hunter Gatherer Research. He and his collaborators recently published an article on the different layers and meanings of the Man the Hunter idea.
Here, Vivek and I lay out those meanings. We talk about how the phrase refers, first, to that popular myth about our evolution, but also to a landmark scientific conference in the 1960s, and to a major finding of research on contemporary hunter-gatherer groups—namely, that men generally do do most of the hunting. We do a little crash-course on the field of hunter-gatherer research, including the kinds of questions it asks and frameworks it uses. We dig into some of the key ingredients of the Man the Hunter myth: the idea that we have aggressive tendencies, the idea that only men hunt, and the idea that hunting played a transformative role in our evolution. We walk through three recent, high-profile studies challenging Man the Hunter ideas in various ways. And we talk about the ever-present danger of projecting our current norms and ideals back in time. Along the way, Vivek and I touch on 2001: A Space Odyssey; reasons why contemporary hunter-gatherers may differ from the hunter-gatherers of long ago; giant sloths; extractive foraging; the case of the Agta, a society in which women do engage in big-game hunting; the forest people and the fierce people; risk and cooperation in sexual divisions of labor; persistence hunting and endurance activities; caregiving and cognition; and honey.
Alright friends, I think you'll enjoy this one. On to my conversation with Dr. Vivek Venkataraman.
 
Notes
3:30 – The article by Dr. Venkataraman and colleagues, 'The Meaning and Dividends of Man the Hunter.' Commentaries on the article can be read here. A recent popular essay by Dr. Venkataraman on the same ideas.
5:00 – Raymond Dart's "killer ape" was originally laid out in a 1953 article 'The Predatory Transition from Ape to Man' (unavailable online) and then developed in Robert Ardrey's book, African Genesis. 
8:30 – The "dawn of man" scene from 2001: A Space Odyssey.
16:00 – The 1966 conference titled 'Man the Hunter' resulted in a 1968 volume of the same name.
27:00 – A philosophical discussion of the use of the "ethnographic analogy" in reconstructions of the past. The paper describing the "tyranny of the ethnographic record."
33:00 – The classic ethnography, The Forest People; the classic ethnography, Yanomamö: The Fierce People.
36:00 – The article by Chris Boehm on the concept of "reverse dominance hierarchy." See also his book Hierarchy in the Forest.
37:00 – Our earlier episode with Brian Hare. 
38:00 – Steven Pinker's widely read and contested book, The Better Angels of our Nature. 
44:00 – A study of the Agta, a society in which women hunt for big game. 
48:00 – The paper by Judith Brown about childcare and subsistence. A paper by Haneul Jang and colleagues about how young girls help mothers during foraging. 
55:00 – For a book-length treatment of hunting in evolution and history, see Matt Cartmill's A View to a Death in the Morning.
1:01:00 – For the 2023 paper by Anderson and colleagues on the prevalence of women's hunting across cultures, see here. For Dr. Venkataraman and colleagues' commentary on the paper, see here. For the related study by Dr. Venkataraman and colleagues about women's hunting, see here.
1:05:00 – For the 2020 paper by Haas and colleagues about female hunters of the Americas, see here.
1:13:00 – For the academic 'Woman the Hunter' papers by Lacy and Ocobock, see here (for the physiology paper) and here (for the archaeology paper). For their article in Scientific American, see here. For an interview on the podcast On Humans with Cara Ocobock, see here.
1:14:00 – For the recent study on persistence hunting in the ethnographic record, see here.
1:20:00 – The authors of the three critiques discussed here have all written commentaries on Dr. Venkataraman and colleagues' paper. These commentaries and others can be read here. 
1:24:30 – For the commentary emphasizing the links between popularization and science, by Nadine Weidman, see here.
1:28:00 – For our earlier episode with Alison Gopnik, in which we discuss the overlooked cognitive capacities involved in caregiving, see here.
1:29:00 – For papers on the importance of honey in human evolution, see here and here. For one of Dr. Venkataraman's own honey-related studies, see here.
 
Recommendations
Creatures of Cain, by Erika Lorraine Milam
The Killer Instinct, by Nadine Weidman
 
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.
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: manymindspodcast@gmail.com.
For updates about the show, visit our website or follow us on Bluesky (@manymindspod.bsky.social).

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 Dr. Elika Bergelson and Dr. Claudia Fugazza. Elika is an Associate Professor in the Department of Psychology at Harvard University, where her lab studies how infants learn language. Claudia is a Researcher at Eötvös Loránd University in Hungary, where she and her collaborators study dogs who are especially gifted word learners. 
In this conversation, Elika, Claudia, and I talk about the thorny question of what it means to understand a word—and whether there are different degrees or kinds of understanding. We consider the challenges posed by different types of words—by nouns, by names, by verbs, by function words, size terms, and more. We discuss why it is that some dogs are so good at learning words, and why infants of a certain age seem to get so much better at it. We talk about learning in different contexts and situations. And we circle the question of how different word learning really is in dogs and babies. 
Alright friends, before we get to it, one tiny ask: If you've been enjoying Many Minds, you can help us grow by leaving a review or comment or a rating, or by sharing us with a friend or colleague. We would greatly appreciate the support!
Without further ado, on to my interview with Claudia Fugazza and Elika Bergelson. Enjoy!
 
Notes
3:30 – A paper on infants' understanding of proper nouns like "Mommy."
6:00 – For our earlier audio essay on names across the animal kingdom, see here.
11:00 – For Dr. Bergelson's early study showing that 6-month-old infants already understand the meanings of some words, see here.
13:30 – For more on the "comprehension boost" in infants after age one, see Dr. Elika's paper here.
16:30 – For Dr. Fugazza and colleagues' first studies on gifted word-learning dogs, see here and here.
20:00 – See earlier studies on Rico and Chaser.
24:00 – For more on the qualitative changes that infants may undergo as they learn to learn words, see a paper by Dr. Bergelson and a colleague here.
30:00 – A study by Dr. Fugazza and colleagues comparing personality profiles and playfulness of gifted word learner dogs and typical dogs.
31:30 – A recent New York Times article consoling readers that having a "dumb" (i.e., non-gifted) dog is okay.
39:30 – A study by Dr. Fugazza and colleagues showing that dogs can extend labels of toys ("pull," "fetch") to new objects that are used in the same way.
43:00 – A study by Dr. Bergelson and a colleague on how broadly (or narrowly) infants apply labels like "foot" or "juice." A study by Dr. Bergelson and colleagues looking at how familiarity affects infants' understanding of words.
52:00 – For an example of a study on the so-called noun bias in early word learning, see here. For work on the (lack of) a noun bias in Tseltal infants, see here. For a sample discussion of the so-called shape bias, see here.
54:00 – For Dr. Fugazza and colleagues' work on dogs' biases toward shape or texture when generalizing about objects, see here.
57:00 – For the work by Asifa Majid (former guest!) on odor words in Jahai, see here. For the work on scent-tracking in humans, see here.
1:02:00 – On "dog-directed speech" and its consequences, see here and here. For comparisons of dog- and infant-directed speech, see here and here.
1:04:00 – For the study finding that Tseltal-speaking children learn honorific terms (which are never addressed to them), see here.
1:06:00 – For the study by Dr. Fugazza and colleagues, "examining exclusion-based choice" in dogs, see here. For the study by Dr. Fugazza and colleagues showing that gifted word learner dogs can learn by over-hearing labels, see here.
1:10:00 – For the study showing that children seem to request labels for objects by pointing to them, see here.
1:12:00 – For some of the first scientific studies on the use of soundboards for communication in dogs, see here and here. For our earlier episode with Dr. Federico Rossano discussing some of this research, see here.
 
Recommendations
'The Invention of Language by Children,' by Lila Gleitman and Elissa Newport
'Concept-based word learning in human infants,' by Jun Yin and Gergely Csibra
'Syntactic bootstrapping as a mechanism for language learning,' by Mireille Babineau et al.
The Genius Dog Challenge YouTube channel
 
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.
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: manymindspodcast@gmail.com.
For updates about the show, visit our website or follow us on Bluesky (@manymindspod.bsky.social).