Understanding sentences with relative clauses

Sentences containing self-embedded relative clauses are generally believed to be difficult to understand because such clauses interrupt the clauses in which they are embedded. However, the experiments that purport to have demonstrated this have confounded the self-embedded or fight-branching location of the relative clauses with their internal structure, comparing self-embedded object relatives with right-branching subject relatives. In order to break this confounding, Experiment I compared the comprehension difficulty of self-embedded and right-branching object relative clauses on two measures of comprehension difficulty. Experiment II made the same self-embedded vs. fight-branching comparison for subject relative clauses. The results of both experiments consistently failed to support the interruption hypothesis.