Show Notes
Can adults still grow new neurons in their brains? You’d think we might know the answer to the question of adult “neurogenesis” after more than half a century of neuroscience research. But it turns out we don’t. In this episode of The Studies Show, Tom and Stuart look into the suprisingly controversial question of adult neurogenesis. Are you “stuck with” the number of brain cells you had as a child, or can you add to that number by making the right choices as an adult? And does it even matter? This podcast is brought to you by Works in Progress magazine, which this week has a new article explaining why nuclear power is so expensive (spoiler: it relies on an incorrect scientific model that we’ve discussed in previous podcast episodes: the “linear no threshold” model. For a full explanation, along with articles on a dizzying array of other progress-related topics, take a look at www.worksinprogress.co. Show notes * Summary post on the debate by Scott Alexander from 2018 * 2000 PNAS study on the brains of London taxi drivers * 2021 retrospective review of taxi driver studies * Study comparing passed vs. failed cabbies on “The Knowledge” * Study putting together neuroimaging research on when the brain peaks in volume and other measures * 1962 Science study on neurogenesis in rats * 1999 BrdU study in macaque monkeys * Famous 1998 study on neurogenesis in the human hippocampus * 2006 PNAS sudy on testing neocortical neurogenesis using Carbon-14 dating * 2013 study using similar methods on the hippocampus * 2018 Nature paper claiming no adult neurogenesis * Associated commentary article * Atlantic article describing the controversy by Ed Yong * 2018 paper finding neurogenesis occuring up to age 79 * 2019 Nature Medicine paper claiming “abundant” adult neurogenesis * Fair-minded 2019 review paper * Somewhat angrier 2021 review paper Credits The Studies Show is produced by Julian Mayers at Yada Yada Productions. We’re grateful to Claire Wang for her help with researching this episode.
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It sounds like a good idea in theory: a non-peer-reviewed scientific journal dedicated to pure scientific creativity. Send in your craziest hypotheses and as long as they’re original ideas, the editor will publish them, and let them inspire the readers. That’s the journal Medical Hypotheses—or, it was. In this episode we discuss some of the maddest papers they ever published, including the one about how wearing heeled shoes causes schizophrenia and an astonishing idea about why humans get acne, and then discuss how the whole thing went wrong. Show notes * “Withdrawn” 2009 Duesberg et al. paper on HIV-AIDS in South Africa * Flensmark (2004) on heeled footwear and schizophrenia * Neuroskeptic’s 2019 investigation into Flensmark * Expressen interview with Flensmark (auto-translated) * 2008 letter proposing ejaculation as a treatment for nasal congestion * Notorious 2007 Down syndrome paper * Ben Goldacre’s piece on it * Judith Rich Harris (2006) on parental selection and human hairlessness * 2014 paper arguing van Gogh had acute porphyria * 2022 paper arguing van Gogh had vestibular migraine instead * “Why do humans get acne? A hypothesis” (2020) * 2024 paper on dummies/pacifiers and SIDS * The original 2013 Brainspotting paper * 2024 Brainspotting debunking in the same journal * “Medical Hypotheses RIP” from sacked editor Bruce Charlton * Charlton’s earlier piece on the journal’s philosophy * 1991 paper on the inflammation–depression hypothesis * 2004 paper on the mitochondrial hypothesis for Alzheimer’s * 2005 gut microbiome/brain paper * 2017 paper “On human parthenogenesis” Credits The Science Fictions podcast is produced by Julian Mayers at Yada Yada Productions.
In 2017, Matthew Walker’s Why We Sleep became a huge bestseller. It said, among other things, that we are living through an epidemic of sleeplessness, that the less we sleep the sooner we die, and that sleeping less than six hours a night doubles your risk of cancer. But are its claims as robust as you might hope? Well, you’ve listened to this podcast before, so what do you think? This podcast is sponsored by Works in Progress magazine. Find endless fascinating pieces on human progress at worksinprogress.co. Show notes * Matthew Walker’s TED Talk (”Sleep is your superpower”) * Bill Gates’s glowing GatesNotes review of Why We Sleep * Alexey Guzey’s 130-hour fact-check of the book’s first chapter — the source for most of this episode * His appendix of reader emails on the anxiety the book caused * On “the shorter your sleep, the shorter your life span” — the two mortality meta-analyses Guzey cites: Cappuccio et al. 2010 and the 2016 dose-response one (both U-shaped, optimum ~7 hours) * On “more than doubling your risk of cancer” — Zhao et al.’s 2018 review in BMC Cancer (65 studies, ~1.55m participants, 86,201 cancers; central OR never above ~1.1) * On whether the West is sleeping less — the review with the table of nationally representative surveys (the table itself) * On the Alzheimer’s claim — the paper suggesting reverse causation (early dementia symptoms include sleeplessness) * The alleged data manipulation: * Yngve Høiseth’s misconduct complaint to UC Berkeley (the deleted graph bar as “falsification”) * Andrew Gelman on “institutional failure” * Scott Alexander’s “If It’s Worth Your Time to Lie, It’s Worth My Time to Correct It” * The cheese wrap reel * What we actually know — the 2024 UK Biobank accelerometer study (~60,000 people; sleep regularity more predictive than duration) * Walker’s 2020 Carl Sagan Prize for Science Popularization — awarded after Guzey’s critique Credits The Science Fictions podcast is produced by Julian Mayers at Yada Yada Productions.
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It’s been a while. Thank you for sticking with us while we’ve been gone. Dozens of countries have started taxing sugary drinks over the last couple of decades. You can see the reasoning: if they cost companies more to make, then companies will pass that cost on to consumers, who will buy less, and hopefully get less fat and then die less often of diabetes and heart disease. But does that actually work? We had a look at the studies behind it. This podcast is sponsored by Works in Progress magazine. Find endless fascinating pieces on human progress at worksinprogress.co. Show notes * Germany’s planned tiered sugar levy — the announcement (and a bit more detail on the €0.26/€0.32-per-litre thresholds) * The WHO’s Global report on the use of sugar-sweetened beverage taxes, 2025 * The World Bank’s Global SSB Tax Database, the source for the “100+ jurisdictions” figure * Chris Snowdon / IEA’s case against sugar taxes: the classic Sugar Taxes: A Briefing and, more recently, The bitter truth about the sugar tax in The Critic * Andreyeva et al.’s 2022 meta-analysis in JAMA Network Open. * Scarborough et al.’s 2020 PLOS Medicine paper on UK reformulation. * The UK Government’s November 2025 Strengthening the Soft Drinks Industry Levy consultation * The substitution question: * 2021 Seattle study (difference-in-difference vs Portland; drinks sugar down, sweets up a bit) * 2025 Chinese modelling paper (the +2.57% total-calorie result in low-income families) * The IZA discussion paper on the UK levy (no substitution to other sweet drinks) * The modelling studies: * 2017 Mexico paper (86–134k diabetes cases “prevented” by 2030) * Scarborough et al.’s 2024 PLOS Medicine PRIMEtime model * Sánchez-Romero et al.’s 2016 PLOS Medicine Markov cohort simulation * The direct, empirical outcome studies: * The 2024 Philadelphia BMI study (the one that found only six prior studies; null panel sample) * The 2025 California study (small effects, wide error bars) * The Mauritius study (no significant BMI association) * The big one — Rogers et al.’s 2023 PLOS Medicine interrupted time series on English schoolchildren (the 8% relative reduction in year 6 girls; 5,234 cases “prevented”) * Chris Snowdon’s demolition of it, including the 2013–2018 counterfactual buried in the supplementary material * Gallup on the recent US obesity decline coinciding with GLP-1 drugs Credits The Science Fictions podcast is produced by Julian Mayers at Yada Yada Productions.