Reblogged:The Trouble With 'No Evidence'

[Gus Van Horn blog]

A recent post by Scott Alexander at Astral Codex Ten makes the following much-needed point about scientific communication that seems head-slappingly obvious ... but only after he makes it after giving us a bunch of real-world examples:

Doesn't that rube know there's 'no evidence' that parachutes prevent deaths? (Image by Ernesto Velázquez, via Unsplash, license.)

... Science communicators are using the same term -- "no evidence" -- to mean:

1. This thing is super plausible, and honestly very likely true, but we haven't checked yet, so we can't be sure.
2. We have hard-and-fast evidence that this is false, stop repeating this easily debunked lie.

This is utterly corrosive to anybody trusting science journalism.

Imagine you are John Q. Public. You read "no evidence of human-to-human transmission of coronavirus", and then a month later it turns out such transmission is common. You read "no evidence linking COVID to indoor dining", and a month later your governor has to shut down indoor dining because of all the COVID it causes. You read "no hard evidence new COVID strain is more transmissible", and a month later everything is in panic mode because it was more transmissible after all. And then you read "no evidence that 45,000 people died of vaccine-related complications". Doesn't sound very reassuring, does it?

One common example from the pandemic -- which he briefly takes up -- is face masks, for which there isn't (as far as I know) conclusive scientific evidence one way of the other of efficacy against Covid transmission, but for which there is a strong common-sense case. And yes, Alexander does mention that it does not serve the cause of clarity to make a big deal out of that lack of a particular kind of evidence.

The whole post is well worth a read, and includes my favorite example of the silliness of demanding that everything be proven through a scientifically rigorous study: the claim one can make that there is "no evidence" that using a parachute helps prevent injuries and deaths when jumping out of planes.

-- CAV

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