DEPTH IN ENGLISH GRAMMAR

Corpus data are used to investigate Yngve's claim that English usage a voids grammatical structures in which the number of left branches betw een any word and the root node of a sentence exceeds some fixed limit. The data do display a marked bias against left-branching, but the pat tern of word-depths does not conform to Yngve's concept of a sharp lim it. The bias could alternatively reflect a statistical invariance in t he incidence of left-branching, but whether this is so depends on how left-branching is counted. Six nonequivalent measures are proposed; it turns out that one (and only one) of these yields strikingly constant figures for left-branching in real-life sentences over a wide range o f lengths. This is not the measure suggested by Yngve's formulation; i t is the measure whose invariance is arguably the most favourable for computational tractability.