Is there any known research on novel language features that are easy to acquire?
I'm most interested in language features that are unexpectedly easy to acquire despite not having an L1 equivalent (so the ease cannot be attributed to transfer).
An international auxiliary language will necessarily include some features that will be novel for some of the people it's intended for.
For example, English has post-nominal relative clauses and Mandarin has prenominal relative clauses and a prospective IAL would have to pick at least one strategy for encoding relative clauses. So some people speaking the language will be using a different word order than they're used to.
I've seen a few papers about second language acquisition regarding syntax and morphology that describe which new constructions are most difficult for specific groups. For example, L1 English speakers learning Mandarin have trouble with the topic comment construction. For example, they will sometimes reject grammatically valid sentences with the object in topic position when asked to distinguish grammatical and ungrammatical sentences.
I have also seen papers like this one that tested English speakers' ability to use a randomly-parameterized variant of a constructed language. The findings are interesting. English speakers are good at reproducing the SOV word order in a novel language, and bad at VSO. This is despite the fact that VSO occurs in English in questions.
