"Sure."

She grins. Seeing Promise smiling is so great. She wants to do more of that.

So, languages. Novial? Sona? Esperanto II?

Results are consistent with it mattering how much a language has ever been used, insofar as they have this information, with some confounding from related conlangs that share vocabulary.

Does it look like a gradation with lots of intermediate steps or a sudden jump from not-understanding to understanding?

There's some gradation, especially in the valley of overlapping vocabulary.

What about... pidgin forms of languages? Creole?

Novel pidgins have the grammar valley thing going on, creoles are understandable as themselves.

"Okay, the usage thing seems solid, how do we falsify that now?"

"You know more about what languages there are to try than I do."

"Well, yeah, but I mean, what kinds of things should I be looking for that this hypothesis wouldn't allow. Very new languages being instantly understandable, I suppose, is the obvious one."

"Or old well-used ones that aren't."

"Yep. I kinda want to nail down what 'well-used' means more precisely but that I think might not actually be possible with our range of available languages."

"Why not?

"'Cause new languages don't really appear very often, and when they do it's usually hard to count how many people actually speak them, or—like, those middle grounds with pidgin languages, hard to keep track of actual usage."

"What's so hard about it exactly?"

"It's... fuzzy? There isn't a boundary that really determines when someone speaks or not a language, and when a language can be said to be itself as opposed to a dialect. And with emerging languages small different sets of people will have different ways of doing it, I think, before anything becomes standard enough."

"...plain speaking is so much easier."

"It is! If there was a way to get mortals it by sorcery or something that would be so useful and also make me even richer."

"People would pay for it?"

"People would pay so much for it. People already pay a lot for several years of training to become conversational in a single other language. Not to mention that it's very hard for a mortal to be as fluent as a native in another language if they learn it after around age ten."

"Well, it'd probably be mental sorcery, which is really, really hard..."

"Yeah, there's that... But if either learning the spell or getting to know someone well enough to cast it on them takes less than, say, twenty or thirty years, it could still be worth it."

"You could probably come to know someone well enough in that time if you hung out with them a lot and they had a particularly open personality."

"How long would it take to actually learn a spell like that, do you think? I'd expect people to know themselves well enough to do it, if it's less than that..."

"Learning the spell wouldn't take nearly as long, but you can't perform mental sorcery on yourself."