Finite adjunct clauses are often assumed to be among the strongest islands for filler–gap dependency creation cross-linguistically, but Kush, Lohndal & Sprouse (2019) found experimental evidence suggesting that finite conditional om-adjunct clauses are not islands for topicalization in Norwegian. To investigate the generality of these findings, we ran three acceptability judgment experiments testing topicalization out of three adjunct clause types: om ‘if’, når ‘when’ and fordi ‘because’ in Norwegian. Largely replicating Kush et al. (2019), we find evidence for the absence of strong island effects with topicalization from om-adjuncts in all three experiments. We find island effects for når- and fordi-adjuncts, but the size of the effects and the underlying judgment distributions that produce those effects differ greatly by island type. Our results suggest that the syntactic category ‘adjunct’ may not constitute a suitably fine-grained grouping to explain variation in island effects.
