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Comment by genxy

18 hours ago

People who would pass The Knowledge test might already develop dementia at a much lower rate.

They could also develop it at the exact same rate and mask it effectively. Had a very sharp family member who was completely lucid through all of dementia, it was like watching a tape rewind. Got to meet each decade's version of them over a couple of years. Towards the end they were completely normal

  • They could easily test for APOE genetics and see if people who carry the risk genes have a lower risk or are less likely to be London cab drivers

  • I don't understand. Do you mean they were lucid, but they believed they were living in a different year? Like thinking adults were still children in school and wondering when dead people were going to call? That kind of thing?

Plausible, but then you'd expect to find the same effect in other people who passed similarly demanding tests once. For example in people who studied something geometry-heavy.

Also, The Knowledge Test is, IIRC, passed only once and then you do not have to retake it for the rest of your career.

If a test passed in your 20s or 30s predicted accurately a much lower incidence of Alzheimer's in your 60s, that would be a remarkably strong early signal. Not impossible, but worth extra scrutiny. For the vast majority of old age conditions, we cannot predict them so long in advance.

  • The Test is repeated every day you get in the cab.

    If you get into a black cab in London and ask to be taken to any location, anywhere within 6 miles of Charing Cross, that driver will know immediately the right route to take without satnav. To get to that point they need to know 25,000 streets and many, many landmarks - statues, museums, galleries, restaurants, hotels, and so on.

    I used to regularly drink with a cabbie in London, and he said that every time somebody got in the back his heart rate would rise, as he'd realise he's "on" and about to have to work out where to head from scratch. Within 30 seconds he'd have every step of the way worked out, down to which lanes at which intersections, no matter where in London he was or where he was going.

    That's the thing that's likely going to reduce Alzheimer's.

  • The point of the test is that you know how to traverse london, and you also know and have a feel for patterns in traffic.

    In the same way that you have code smell.

    Granted, some use GPS, but most only really use it for pickup