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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Seven metaphors for AI
Many Minds
If you wanted a petri dish for understanding metaphors—how they emerge and evolve and jostle with each other—it would be hard to do better than the world of AI. We talk about AI systems variously as coaches or co-pilots, little genies or alien intelligences. Some researchers claim that AIs "grow," that they're entering their phase of "adolescence." Critics deride AI products as slop and dismiss LLMs as a kind of autocomplete on steroids. What's behind these different characterizations? Which ones are accurate and which are unfair? And are our metaphors mostly colorful rhetoric or do they...
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Origins of the kiss
Many Minds
Humans do some pretty weird things. Some of us will sit in searingly hot rooms or jump into icy ponds. Others risk their lives trying to climb to new heights or dive to new depths. And every once in a while, two otherwise normal-seeming humans will lean in close to each other, open mouths, lock lips, and swap a hearty helping of microbes. You may even know people who've done this. But why? Are we the only animals who kiss? What could be the deeper origins of this truly bizarre behavior? My guest today is Dr. . Matilda is an Evolutionary Biologist at the University of Oxford. She's...
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The aura of metaphor
Many Minds
Metaphors matter. They enliven our speech and our prose; they animate our arguments and stir our passions. Some metaphors power political movements; others propel scientific revolutions. These little figures of speech delight, provoke, captivate, shock, amuse, and galvanize us. In one way or another, metaphors just seem to help us make sense of a messy world. But how do they do all this? Whence their peculiar powers? What does it say about the human mind that we just can’t escape our metaphors—and frankly don’t want to? My guest today is . Steve is an Assistant Professor of...
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From the archive: How should we think about IQ?
Many Minds
Hello friends, and happy new year! We're gearing up for a new run of episodes starting later in January. In the meanwhile, enjoy this pick from our archives. ------ [originally aired October 16, 2024] 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...
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From 'On Humans': Can the brain understand itself?
Many Minds
Hello there, friends! We hope you're having a restful holiday, or a lively holiday, or whatever mix of those you prefer. As the year draws to a close, we at Many Minds are taking a much needed pause ourselves. But we wanted to share with you an episode from a podcast that we've been following for some time called . It's hosted by Ilari Mäkelä. It looks at humanity from all angles to understand where we come from and where we're going. The episode we're sharing features an interview with biologist and historian of science, Matthew Cobb; he's also the author of the book, . In...
info_outlineHello friends, and happy new year! We're gearing up for a new run of episodes starting later in January. In the meanwhile, enjoy this pick from our archives.
------
[originally aired October 16, 2024]
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 worse. There's no question, after all, that IQ has been misused—that it still gets misused—for all kinds of racist, classist, colonialist purposes. As if this wasn't all thorny enough, the study of IQ is also intimately bound up with the study of genetics. It's right there in the roiling center of debates about how genes and environment make us who we are. So, yeah, what to make of all this? How should we be thinking about IQ?
My guest today is Dr. Eric Turkheimer. Eric is Professor of Psychology at the University of Virginia. He has studied intelligence and many other complex human traits for decades, and he's a major figure in the field of “behavior genetics.” Eric also has a new book out this fall—which I highly recommend—titled Understanding the Nature-Nurture Debate. In a field that has sometimes been accused of rampant optimism, Eric is—as you'll hear—a bit more measured.
In this conversation, Eric and I focus on intelligence and its putatively genetic basis. We talk about why Eric doubts that we are anywhere close to an account of the biology of IQ. We discuss what makes intelligence such a formidable construct in psychology and why essentialist understandings of it are so intuitive. We talk about Francis Galton and the long shadow he’s cast on the study of human behavior. We discuss the classic era of Twin Studies—an era in which researchers started to derive quantitative estimates of the heritability of complex traits. We talk about how the main takeaway from that era was that genes are quite important indeed, and about how more recent genetic techniques suggest that takeaway may have been a bit simplistic. Along the way, Eric and I touch on spelling ability, child prodigies, the chemical composition of money, the shared quirks of twins reared apart, the Flynn Effect, the Reverse Flynn Effect, birth order, the genetics of height, the problem of missing heritability, whether we should still be using IQ scores, and the role of behavior genetics in the broader social sciences.
Alright folks, lots in here—let's just get to it. On to my conversation with Dr. Eric Turkheimer. Enjoy!
A transcript of this episode is available here.
Notes and links
3:30 – The 1994 book The Bell Curve, by Richard Herrnstein a Charles Murray, dealt largely with the putative social implications of IQ research. It was extremely controversial and widely discussed. For an overview of the book and controversy, see the Wikipedia article here.
6:00 – For discussion of the “all parents are environmentalists…” quip, see here.
12:00 – The notion of “multiple intelligences” was popularized by the psychologist Howard Gardner—see here for an overview. See here for an attempt to test the claims of the “multiple intelligences” framework using some of the methods of traditional IQ research. For work on EQ (or Emotional Intelligence) see here.
19:00 – Dr. Turkheimer has also laid out his spelling test analogy in a Substack post.
22:30 – Dr. Turkheimer’s 1998 paper, “Heritability and Biological Explanation.”
24:30 – For an in-passing treatment of the processing efficiency idea, see p. 195 of Daniel Nettle’s book Personality. See also Richard Haier’s book, The Neuroscience of Intelligence.
26:00 – The original study on the relationship between pupil size and intelligence. A more recent study that fails to replicate those findings.
31:00 – For an argument that child prodigies constitute an argument for “nature,” see here. For a memorable narrative account of one child prodigy, see here.
32:00 – A meta-analysis of the Flynn effect. We have previously discussed the Flynn Effect in an episode with Michael Muthukrishna.
37:00 – James Flynn’s book, What is Intelligence? On the reversal of the Flynn Effect, see here.
40:00 – The phrase “nature-nurture” originally comes from Shakespeare and was picked up by Francis Galton. In The Tempest, Prospero describes Caliban as “a born devil on whose nature/ Nurture can never stick.”
41:00 – For a biography of Galton, see here. For an article-length account of Galton’s role in the birth of eugenics, see here.
50:00 – For an account of R.A. Fisher’s 1918 paper and its continuing influence, see here.
55:00 – See Dr. Turkheimer’s paper on the “nonshared environment”—E in the ACE model.
57:00 – A study coming out of the Minnesota Study of Twins reared apart. A New York Times article recounting some of the interesting anecdata in the Minnesota Study.
1:00:00 – See Dr. Turkheimer’s 2000 paper on the “three laws of behavior genetics.” Note that this is not, in fact, Dr. Turkheimer’s most cited paper (though it is very well cited).
1:03:00 – For another view of the state of behavior genetics in the postgenomic era, see here.
1:11:00 – For Dr. Turkheimer’s work on poverty, heritability, and IQ, see here.
1:13:00 – A recent large-scale analysis of birth order effects on personality.
1:16:00 – For Dr. Turkheimer’s take on the missing heritability problem, see here and here.
1:19:00 – A recent study on the missing heritability problem in the case of height.
1:30:00 – On the dark side of IQ, see Chapter 9 of Dr. Turkheimer’s book. See also Radiolab’s series on g.
1:31:00 – See Dr. Turkheimer’s Substack, The Gloomy Prospect.
Recommendations
The Genetic Lottery, Kathryn Paige Harden
Intelligence, Stuart Ritchie
Intelligence and How to Get It, Richard Nisbett
"Why our IQ levels are higher than our grandparents’’ (Ted talk), James Flynn
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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