You missed the working part. Success was a prerequisite to their after the fact feelings. At least some of the control group will be in old age but still alive when we know it woris. They might not know if it is infinite life (and side effects may turn it into die at 85, so some control may outlive the intervention group after the study ), but they will know on average they did worse

> At least some of the control group will be in old age but still alive when we know it woris.

The anti-aging serum could work (i.e. make you older), but have strong negative side effects.

So then it wouldn't "work", where "work" as used here is defined, "to function or operate according to plan or design".

And no, it's not reasonable to assume I meant "work" as in, "have an anti-aging serum that has strong negative side effects."

An anti-aging serum works if it reduces or removed specific (or even most/all?) effects that are related to aging.

Relative to other side effects. Remember we are in a post serum existing scenario so we would have the knowledge of those as part of the discussion on if it works.

People opt into the study in the first place. I'm willing to bet that no one opts into the study hoping to be in the control group.

Well, some medical studies pay good money, so it's perfectly rational to sign up for these and hope to get the placebo.

Fair enough. I tend to think of most of them as paying just a small amount where the main goal is to get treatment, but I'm sure some pay better than others.