Swedish relative clause (RC) extractions are allegedly acceptable despite a universal constraint on NP extraction (Erteschik-Shir, 1973). In two eye-tracking experiments, we investigated the processing of RC extractions in Swedish by manipulating the plausibility of NP fillers relative to RC predicates. A similar study on English RCs (Traxler & Pickering, 1996) found plausibility effects in English for non-island but not island conditions, indicating a lack of integration in islands.

Experiment 1 tested for plausibility effects in extractions from RCs (alleged non-islands), that-clauses (non-islands), and non-restrictive RCs (islands; Engdahl, 1997). We expected that only the first two would show sensitivity to plausibility. Surprisingly, we found effects, and thus integration for all three structures. Experiment 2 tested for plausibility effects in RCs embedded in subjects (islands) vs. objects (non-islands). The RC verbs (optionally transitive) provided a potential gap and were hypothesized to allow for integration in the object condition only. A following clause provided the real gap. Again, we found plausibility effects for both conditions at the RC verb, suggesting integration. Our study calls into question the correspondence between acceptability- and processing-based metrics of Swedish islandhood and raises the possibility of cross-linguistic variation with regard to the processing of island violations.