Author Extra: Joshua Foer Answers Audience Questions

Q: Can your guest please comment on the memory requirements for London cab drivers? How do they successfully pass what I understand is the most challenging memory test for employment out there? – From Parvinder in Arlington

A: In order to be certified as a London cabbie, you have to pass a daunting test called “the Knowledge,” which involves memorizing the locations and traffic patterns of all 25,000 streets in London, which is an incredibly confusing city. For cabbies-in-training the training is a matter of sheer repetition. They will spend two to four years driving all over the streets of London memorizing street names and landmarks. In 2000, a neuroscientist at University College London named Eleanor Maguire wanted to find out what effect, if any, all that driving around the labyrinthine streets of London might have on the cabbies’ brains. When she brought sixteen taxi drivers into her lab and examined their brains in an MRI scanner, she found one surprising and important difference. The right posterior hippocampus, a part of the brain known to be involved in spatial navigation, was 7 percent larger than normal in the cabbies—a small but very significant difference. Maguire concluded that all of that way-finding around London had physically altered the gross structure of their brains. The more years a cabbie had been on the road, the more pronounced the effect.

Q: What is one or some of the historical pieces of architecture that is considered a “good” memory palace? – From Sarah in Orlando

A: Medieval memory treatises go into some depth on this subject. One type of building they advise makes for a terrible memory palace is churches. All those naves and rows of pews are repetitive and unmemorable. And most churches look alike. The best buildings to turn into memory palaces are those that are architecturally distinct, and have lots of nooks to nip that you can dip into in your mind’s eye and deposit images.

Q: My almost two-year old son has an amazing memory for his age. He has memorized nursery rhymes, songs, and parts of stories. He asks me to repeat things over and over and (although I sometimes feel like a juke box) and I’m happy to oblige. He will also talk about something that happened on a visit to a friend’s house, or a child he met a playground, days and even weeks after it happened. I thought that our brains weren’t capable of remembering things before the age of 3. How early does memory start? Will my child remember “Gus run with Kyla in park. Park muddy.” or “Gus sit Stacey’s lap at Jack’s house” years from now? – From Kathy in Arlington

A: Infantile amneisa is a fascinating phenomenon that I write about in Moonwalking with Einstein. Most of us don’t remember anything before the age of about three or four. And yet, as you point out, it’s not as if a three-year-old doesn’t remember anything. In fact, he may remember a lot. But those memories are likely to be forgotten as an adult. Freud thought that infantile amnesia was a result of the grown-up mind repressing the hyper-sexualized fantasies of toddlerhood. I’m not sure you’d find anyone who agrees with that hypothesis these days. In fact, it seems to be the case that regions of the brain crucial to memory are not fully formed until about the fourth year.