Evaluation of dependency parsers on unbounded dependencies

We evaluate two dependency parsers, MSTParser and MaltParser, with respect to their capacity to recover unbounded de-pendencies in English, a type of evalu-ation that has been applied to grammar-based parsers and statistical phrase struc-ture parsers but not to dependency parsers. The evaluation shows that when combined with simple post-processing heuristics, the parsers correctly recall unbounded dependencies roughly 50 % of the time, which is only slightly worse than two grammar-based parsers specifically de-signed to cope with such dependencies.