One in five children infected in the recent London measles outbreak were reportedly hospitalised.
Don’t believe the anti-vaxxers when they say “it’s a mild disease” or “it’s better to get immunity naturally”.
It isn’t.

“At least 34 children have been infected by a "fast-spreading" measles outbreak in several north London schools, health officials have said.”
https://www.bbc.co.uk/news/articles/cev7edxxzm7o

Because the world was so well prepared last time!
https://www.nature.com/articles/d41586-026-00468-1

You can find a longer version of this thread in my latest substack article:
https://open.substack.com/pub/kityates/p/middle-bias-at-the-bbc?r=1cw8pl&utm_campaign=post&utm_medium=web&showWelcomeOnShare=true
10/10

I also explored other counterintuitive probability puzzles—like the Birthday problem and Monty Hall—with Alex & Emily.
Hear the episode: https://www.bbc.co.uk/sounds/play/w3ct6sv0
Or pick up How to Expect the Unexpected: https://uk.bookshop.org/lists/kit-yates-books?&new-list-page=true
9/10

And even in public toilets—middle cubicles can be up to 50% more likely to be chosen than outer ones: https://doi.org/10.1111/j.1467-9280.1995.tb00304.x

Was middle bias affecting the producers’ choices? Hard to say—but it's one of many ways randomness surprises us.
8/10

Similarly, educational psychologists find that students who don’t know the answer tend to pick the middle options:
https://doi.org/10.1111/j.1745-3984.2003.tb01099.x

The same happens in Battleship, on shelves, dropdown menus:
https://doi.org/10.1177/1745691615588092
7/10

One key bias is middle bias - favouring central options and avoiding extremes.
Behavioural scientists have shown that adding an 'ultra‑premium' option to an initial offering of 'premium' and 'basic' makes the premium option (now middle) more popular
https://doi.org/10.1086/208899
6/10

We’re bad at spotting randomness, but also bad at being random. Ideally answers A/B/C should be chosen with equal probability.
Any systematic bias lets sharp listeners like Griffith pick up patterns and beat the 1/3 odds.
5/10

While I can’t speak for the producers (they explain their reasoning on the programme), it seemed to me the issue was our species’ difficulty with randomness.
A major theme of my second book How to Expect the Unexpected:
https://uk.bookshop.org/p/books/how-to-expect-the-unexpected-the-science-of-making-predictions-and-the-art-of-knowing-when-not-to-kit-yates/7328813?ean=9781529408690
4/10

They wanted to answer a question from Griffith in Ghana about Unexpected Elements (https://www.bbc.co.uk/programmes/p016tmt2).
He’d noticed the quiz answers were often B or C, but rarely A—and wanted to know why.
3/10

A couple of weeks ago I had the BBC Crowd Science team over - producer Emily Knight & presenter Alex Lethbridge - to talk about probability in all its surprising forms.
We ended up diving deep into patterns, biases, and randomness itself.
Listen here: https://www.bbc.co.uk/sounds/play/w3ct6sv0
2/10

Ever notice that multiple‑choice quizzes often feel strangely predictable? I recently dug into why answers so often sit in the middle—and what this reveals about our deep, systematic difficulty with randomness. It’s more surprising than you might think. 🧵
1/10