alt Hacker NewsOK, I'll bite. I want to know more of the reasoning behind this, because I think it implies that S-expressions are alien to the innate/evolved syntactic knowledge in human languages. A lot of American linguistics, like Chomsky's gropings for how to construct universal grammar and deep syntax trees, or the lambda calculus of semantic functions, looks like S-expressions, and I think that's because there was some coordination between human linguists and computer science (Chomsky was, after all, at MIT). At the same time, I've had a gut instinct that these theories described some languages (like English) better than others (like ancient Greek), requiring more explanation of changes between deep structure and surface structure for languages that were less like English. If models trained on actual language handle s-expressions poorly, that could imply that s-expressions were not a good model for the deep structure of human language, or that the deep-structure vs surface-structure model did not really work. I'd be very happy to learn more about this.
S-expressions are just lists and trees. That’s it. If a language has groups of words and any hierarchy, you can use s-expressions to represent it. Sure, some human languages might be more or less flat and the groups might represent different things, but I don’t see how that prevents s-expressions from being suitable. Greek doesn’t rely on word order nearly as much as English (it does more with suffixes to indicate subject and object, for instance), but all of that can still be represented in s-expressions.