Asymmetries in relative clause comprehension in three European sign languages

Relativization is a robust subordinating type across languages, displaying important typological variability concerning the position of the nominal head that the relative clause modifies, and sign languages are no exception. It has been widely assumed since Keenan & Comrie (1977) that the subject position is more accessible to relativization than object and oblique positions. The main aim of this paper is to investigate the extension of this famous generalization both across modalities (sign as opposed to spoken languages) and across relativization typologies (internally as opposed to externally headed relatives), and to verify how it interacts with age of first language exposure. We here report the results of a sentence-to-picture matching task assessing the comprehension of subject and object relative clauses (RCs) in three sign languages: French Sign Language (LSF), Catalan Sign Language (LSC), and Italian Sign Language (LIS). The results are that object RCs are never easier to comprehend than subject RCs. Remarkably, this is independent from the type of relative clause (internally or externally headed). As for the impact of age of exposure, we found that native signers outperform non-native signers and that a delay in language exposure emphasizes the subject/object asymmetry. Our results introduce a new potential diagnostic for LF movement: the existence of a Subject Advantage in comprehension can be used as a reliable and measurable cue for the existence of long-distance dependencies, including covert ones.