How hierarchical is language use?

Stefan L. Frank, Rens Bod and Morten H. Christiansen have written an interesting paper on the topic "How hierarchical is language use?". The paper has been published in the Proceedings of the Royal Society, online since 12th of September, 2012. This contribution is an important addition to the chain of critical arguments on Chomskyan view of linguistics. In the paper, the authors state, e.g., that

"[i]t is generally assumed that hierarchical phrase structure plays a central role in human language. However, considerations of simplicity and evolutionary continuity suggest that hierarchical structure should not be invoked too hastily. Indeed, recent neurophysiological, behavioural and computational studies show that sequential sentence structure has considerable explanatory power and that hierarchical processing is often not involved. In this paper, we review evidence from the recent literature supporting the hypothesis that sequential structure may be fundamental to the comprehension, production and acquisition of human language."