The current work tests the hypothesis that the island status of clausal adjuncts, as determined by judgments on wh-questions, are predicted by the degree of “backgroundedness” of the adjuncts, as determined by a separate negation task. Results of two experiments support the hypothesis that acceptability of extraction from adjuncts in wh-questions is inversely correlated with the degree to which the adjunct is backgrounded in discourse. Taken together, results show that temporal clausal adjuncts (headed by before, after, while) are stronger islands than adjuncts that are causal (here, headed by to or by). This demonstrates that adjuncts differ in degree of island status, depending on their meaning, despite parallel syntactic structure.