Secrets of the Brain

To accompany his BBC4 series The Brain, neuroscientist David Eagleman reveals some fascinating facts you may not have known about what's inside your head


“If I gave you a hundred billion pieces of Lego with pulleys and levers,” says David Eagleman, “and you hooked up this this incredibly complex system and set it going, at what point do you say: Okay now it’s experiencing the taste of feta cheese?”


The American neuroscientist is explaining that despite remarkable recent advances in the fields of robotics and computer science we are very unlikely to ever invent a machine as complex as the human brain. “After all,” he adds, “Mother Nature has been running trillions of experiments in parallel for billions of years and as a result she has come up with some really good tricks.”

Ahead of his six part BBC4 series exploring the sheer diversity and wonder of those tricks, Eagleman picks out a handful of remarkable facts about the stuff inside your head.

Half a brain

Before the age of eight it is possible to remove half of the brain (a surgical procedure known as a hemispherectomy) and the other half of the brain will rewire itself to take over the missing functions. The kid will turn out fine! 

All in your head

The world you experience, the black cabs, cats and dogs, budgerigars is all happening inside your head. Trapped in silence and darkness in the vault of your skull, all your brain ever sees are electro-chemical signals bouncing around – out of that it extracts patterns to construct your private subjective reality. Colours are an invention of the brain. There are no purples, reds or blues just wavelengths of light, electromagnetic radiation. The brain converts those different wavelengths into the colours we perceive.

Looks familiar

People believe vision is like a video camera – a signal goes through your eyes and into your brain and you see something. But vision is all about activity inside your head. The brain has an internal model and it uses the little bit of external data that comes trickling through the eyes to make comparison with that model to create what we see. That’s why, for instance, when a prisoner at Alcatraz was put into a blacked out solitary confinement cell he started seeing things – he was creating his own reality because his brain’s internal model was still running.

It pays to be curious

If you are curious about something and find the answer while you are still curious that answer will stick in your memory. That’s because the right cocktail of neurotransmitter chemicals is present in your brain. Find the answer out later, when you are no longer curious and the cocktail has changed and you are less likely to remember it.

Brains are getting better

Coming generations are going to be a lot smarter than we are. A child playing educational games on an iPad, learning his or her alphabet and numbers with adaptive software tailored to their individual responses are undergoing as kids an intense tailored education. Young brains have never experienced that degree of training before.

Train your brain

The brain is not a muscle – it’s actually three pounds of Jell-o like material – but you do need to exercise it, the brain is constantly forming and reforming roadways (in a cubic centimetre of brain tissue there are as many connections as stars in the Milky Way) and they have to be used.

You are your brain 

Your brain is the densest representation of who you are. Damage a tiny part of your brain that can change you entirely – your personality, your decision-making, and your risk aversion. Damage another part of your body and you might be sad about it but you are not very different as a person.

Your brain is greater than the sum of its parts

The brain has what neuroscientists call emergent properties. A hunk of metal doesn’t have the property of flight but if I get enough hunks of metal together in the shape of airplane then that has the property of flight. Likewise each of the brain’s hundred billion cells is just a dumb little cell running its own little programme. But get enough of those doing their own thing and you have the human mind.

Our brains need other brains

An enormous amount of our brain circuitry comes from interaction with other people’s brains – we have specific networks that communicate with other brains and monitors other people’s intentions and moods.


The Brain with David Eagleman is on Thursdays at 9pm on BBC4