Dr. David Eagleman: Stanford neuroscientist, New York Times bestselling author (Livewire), and researcher in brain plasticity, perception, and synesthesia. Known for studying how experience physically reshapes the brain.
What this episode covers
Eagleman and Bartlett explore how the brain is a constantly changing, plastic organ that can be actively reshaped by seeking challenge and novelty. They discuss why fluid intelligence in childhood gives way to crystallized intelligence in adulthood, why retirement and shrinking social lives accelerate cognitive decline, and how building 'cognitive reserve' guards against dementia. A large middle section debates AI: the difference between vicious and virtuous friction, why AI is creative but bad at selection, and why humans will increasingly value live, in-person connection. Eagleman closes with his new theory that dreaming exists to defend the visual cortex from being taken over by other senses during nightly darkness.
The guest's own work
Livewire: The Inside Story of the Ever-Changing Brain
David Eagleman
“I'm going to link your book below um so everyone can read this book... It was actually learning about this subject matter in LiveWire that helped me”— Steven Bartlett
The Ulysses Contract (forthcoming, 2027)
David Eagleman
“You've got a new book on the way... That's about the Ulisses contract and that'll come out in 2027.”— David Eagleman
Also referenced (named, not recommended)
Foundation
Isaac Asimov
“I saw an interview with Isaac Azimoff in 1988. He was the great science fiction writer who wrote Foundation and so many other books.”— David Eagleman
Encyclopaedia Britannica
Encyclopaedia Britannica
“I would pick up the Encyclopedia Bratannica and I would flip through it and hope they had an article about the thing that I wanted to know about”— David Eagleman
Tesla Full Self-Driving
Tesla
“I last year got a Tesla with full self-driving and I was watching as it was full self-driving... it slowed down and came to a stop, which was exactly the right thing.”— David Eagleman
ElevenLabs
ElevenLabs
“did you know David that you can you know use uh 11 labs and hey Jen and you know you can make an avatar of yourself and you can use your voice”— David Eagleman
HeyGen
HeyGen
“you can you know use uh 11 labs and hey Jen and you know you can make an avatar of yourself and you can use your voice”— David Eagleman
Big reveals from this episode
- Eagleman reveals his theory: we dream to defend the visual cortex from being taken over by the other senses during darkness.
- Claims your brain peaked at age two, when neural connections are densest, and has been pruning ever since.
- Cites the religious orders 'nun study' where some nuns had Alzheimer's-ravaged brains but no cognitive symptoms due to cognitive reserve.
- Declares himself a 'cyber optimist' who thinks the internet will make the next generation smarter, not dumber.
- Reveals he has aphantasia (no visual imagery), and that many of Pixar's best animators are aphantasic too.
- States that if Earth didn't rotate into darkness, humans presumably wouldn't dream at all.
- Predicts a 2026 market opportunity for a new social network built to connect people rather than maximize engagement.
Worth remembering
- The brain has about 86 billion neurons; Eagleman describes the self as a 'team of rivals' of competing neural networks.
- Romanian orphans deprived of touch and talk grew up with lasting cognitive deficits, showing plasticity's downside.
- The anterior mid-cingulate cortex is bigger in people who repeatedly do hard things they don't want to do.
- You can tell a pianist from a violinist by the brain alone, because violinists develop fine-motor cortex on only one side.
- The 'effort phenomenon': people pay more for art or natural diamonds that seem to have taken more effort.
- Eagleman defines all creativity as bending, breaking, and blending existing concepts into new remixes.
- At least 3% of people have synesthesia, a blending of senses where letters or sounds trigger colors.
- Brain plasticity correlates almost perfectly with how much an animal species dreams (measured via REM).
- The blind mole rat still dreams despite having lost vision, because the dream circuitry is evolutionarily ancient.
- By one estimate, around a billion people are now in relationships with AI companions.