Non-crossing Dependencies: Least Effort, not

Abstract The use of null hypotheses (in a statistical sense) is common in hard sci-ences but not in theoretical linguistics. Here the null hypothesis that the low fre-quency of syntactic dependency crossings is expected by an arbitrary ordering of words is rejected. It is shown that this would require star dependency structures, which are both unrealistic and too restrictive. The hypothesis of the limited re-sources of the human brain is revisited. Stronger null hypotheses taking into account actual dependency lengths for the likelihood of crossings are presented. Those hy-potheses suggests that crossings are likely to reduce when dependencies are short-ened. A hypothesis based on pressure to reduce dependency lengths is more parsi-monious than a principle of minimization of crossings or a grammatical ban that is totally dissociated from the general and non-linguistic principle of economy.