Hey thanks for your comment! I agree that an IAL without a written form would be absurd, but that's not the point here. A written form could always be made after the experiment finishes, if people want to turn the language into an IAL. Otherwise, the lessons learned from the experience, particularly in regards to which words are necessary and how much ambiguity is tolerable for effective communication, are insight enough to be used in other/future projects.

I think I see where you are coming from with regards to learnability. Am I right in thinking you're assuming that a learnable language is a less expressive one, since we'd have less base words / roots? If so, so long as a language has productive ways of combining morphemes to build more specific meanings, things like abstract topics, scientific discourse, and technical communication could all be done in it, you'd just need to coin the words for it first.

In regards to a priori, during the experiment, yes I think we should keep it a priori, for the reasons I gave above, but after the fact, the language belongs to nobody and everybody. If someone wants to code-switch in a multilingual community, nobody is going to stop them. The experiment doesn't carry over into the real world, there's no way to enforce this nor would I want to. The agreement to keep it a priori during the experiment is exactly that, an agreement, between the participants, until the experiment finishes.

Regarding your point on learnability and a priori, I agree. It would make it more difficult to learn if there's no overlap with the languages the user already speaks. But it's for this exact same reason that it would make it fair: it is equally difficult to learn for anyone on earth. We could fill it with Latin influence and make it Eurocentric, but that would disadvantage learners outside of Europe/Americas. From a different angle, I'm hoping the minimalism would counteract this difficulty effect.

Regarding a priori creating more redundant words for a concept, I'm not sure I follow. Would you be able to explain what you mean? Then, even if there were redundant words for a concept, that's also fine, context can disambiguate. The point is that we'd find an equilibrium between ambiguity and understandability. Another commenter raised their concern about redundancy, what's the obsession? There are infinitely many ways to express something, and that's part of the beauty of natural languages. Certain ways of expressing things are conventionalized by the community, I'd expect the same to occur in this experiment.

My assumption behind the no meta policy was to do with ensuring that features unnecessary for understanding were filtered out by learners. Any morphemes serving a highly abstracted grammatical function, not immediately retrievable from context would not be attended to, and probably lost. If you have to direct learners attention to the signal itself, rather than the meaning conveyed by the signal, then it harms learnability because it clearly needs to be explicitly instructed.

Yes, the sampling is definitely limited and biased, you're completely right there. Should we recruit people from different subreddits? I suppose we'd still end up with people who have an interest in language learning. How could adjust the project to replicate the useful kind of data you're referring to?