I'm not saying I'm surprised they believe something that isn't true. We all do, myself included I'm certain. But some things would be trivial to test to see if it's true or not.

I used to think carrots made your eyesight better, because that's what I was taught. I've since let go of that belief in light of new understanding and evidence. That is a claim that's harder to demonstrate, so it takes time to learn the truth of the matter.

If was selling you a charm that made you bulletproof, it would be trivial to demonstrate. I'd wear it and you'd shoot me and I would be unharmed. But I'd wager money that no vendor selling such a charm would ever agree to such a simple demonstration of their wares.

Yes, but some misconceptions are easier to disprove. And some misconceptions are genuine (in the sense that people genuinely believe them) and others are mere scams that even their alleged "believers" don't believe.

I know at least one source for the misconception that carrots make your eyesight better: a WW2 lie to hide the fact of the existence of either radar or encryption breaking (I forget which).

But someone who actually believed carrots make your eyesight better might try to test it for themselves. They may even keep on deluding themselves after doing an experiment (hey, the placebo effect is strong).

What about someone who believes a juju amulet makes them impervious to stabbing. Would they be willing to try it? You offer to stab at their heart with all your might, and if they survive you give them money. Do they accept your offer? If they don't -- and they never do -- what is happening is that they suspect it doesn't really work.

It reminds me of Jack London's story, "Lost Face": https://americanliterature.com/author/jack-london/short-stor...