The Brain summary

Life may be unpredictable. But there is one constant – people change. Sometimes we improve and mellow with age, like a good wine. Sometimes, like a once-decent vintage that turns to vinegar, we sour and become unpalatable.

You may have experienced the personality-altering effects of time. Ever met up with a friend from your school days and found yourself wondering what happened to the person you once knew? How can someone change so much? What’s the science behind it?

Well, it’s all about how the brain changes over time. From birth onward, our brains are constantly making new connections and adapting to new situations. This shapes our personalities.

Take a two-year-old child. Her brain has the same number of brain cells but twice as many synapses – connections which transmit information – as an adult. This is because, as humans age, they lose the synaptic connections that haven’t been reinforced by constant repetition. Think of language. It’s difficult to mimic or distinguish the sounds of foreign languages because you weren’t exposed to them as a child.

This applies to personality more generally. The synaptic connections that make you you are the result of everything you’ve ever been exposed to. In other words, every person you meet, film you watch or book you read shapes who you are!

Call it plasticity. That’s a fancy term for the brain’s ability to “learn” by repetition – an ability that’s certainly not restricted to children. Adult brains are also capable of change.

This was shown in a study carried out by scientists at University College London. They scanned the brains of some of the city’s taxi drivers and found that they possessed larger hippocampi – the hippocampus is the part of the brain responsible for spatial memory – than the control group.

The explanation? Cabbies have what’s called “the Knowledge” – a precise memory of London’s 25,000 streets, 20,000 landmarks and 320 different routes, which each of them acquired during four years of training.

Spending so much time exercising their memories meant that the cab drivers strengthened certain connections in their brains. It’s a bit like a workout; the targeted area grew as a result of constant use.

That sort of change can also have a dramatic effect on personality.

Maybe you’ve heard of Charles Whitman, the man who murdered his wife and mother, and then shot and killed another 13 people with a rifle from atop a tower at the University of Texas, back in 1966. What you might not know is that a postmortem carried out after he’d been shot to death found a tumor in his brain. It was located in the part that’s responsible for fear and aggression.