Subject islands do not reduce to construction-specific discourse function

A central question about our shared capacity for language is how it is integrated with other cognitive systems. One important debate focuses on the extent to which the form of linguistic expressions is grounded in their communicative function: Can all constraints on linguistic form be attributed to the way constructions package information, or is linguistic form autonomous of meaning and function? One area of disagreement involves islands: phrases which block the formation of long-distance filler-gap dependencies (Ross, 1967). Grammatical subjects are considered islands, since questioning a sub-part of a subject results in an ill-formed sentence, e.g., "Which topic did the article about inspire you?". Autonomous syntactic approaches to islands attribute this ungrammaticality to the abstract movement dependency between the wh-phrase and the subject-internal position with which it is associated. An alternative developed in Abeillé et al. (2020) suggests that subjects' island status is specific to the information structure of wh-questions, suggesting that subjects are not islands for movement, but for focusing, due to their discourse-backgroundedness. This predicts that other constructions that involve movement but not focusing should not create a subject island effect. We test this in three acceptability studies, using a factorial design to isolate subject island violations across three constructions: wh-questions, relative clauses and topicalization. We find a subject island effect in each case, despite only wh-questions introducing what Abeillé et al. (2020) call "a clash in information structure". We argue that this motivates an account of islands in terms of syntactic representations shared across constructions, independent of communicative function.