Xenolinguistics: the scientific study of languages of non-human intelligences. Publications in this field tend to be speculative as few people have made the claim to have understood an alien language, at least not reliably.
Hallucinations as Alien Art
The key to this discussion is a conceit of the extraordinary vision-producing ability unleashed in consciousness by psychedelics, as alien art: aesthetic productions of an unknown, hence alien, source. Whether the alien is an unknown (normally unconscious) aspect of the Self, an Other,