Branching (linguistics) - Binary Vs. N-ary Branching

Binary Vs. N-ary Branching

Much work in Government and Binding Theory (GB), the Minimalist Program (MP), and Lexical Functional Grammar (LFG) takes all branching to be binary. Other theories (both constituency- and dependency-based ones), e.g. early Transformational Grammar, Head-Driven Phrase Structure Grammar, Meaning-Text Theory, Word Grammar, etc. allow for n-ary branching. This distinction can have a profound impact on the overall nature of the theory of syntax. The two main possibilities in a phrase structure grammar are illustrated with the following trees:

The binary branching on the left is closely associated with the structures of GB, MP, and LFG, and it is similar to what the X-bar schema assumes. The n-ary branching structure on the right is a more traditional approach to branching. One can muster arguments for both approaches. For instance, the critics of the strictly binary branching structures charge that the strict binarity is motivated more by a desire for theoretical purity than by empirical observation.

Strictly binary branching structures increase the amount of syntactic structure (number of nodes) to the upper limit of what is possible, whereas flatter n-ary branching tends to restrict the amount of structure that the theory can assume. Worth noting in this area is that the more layered the syntactic structures are, the more discontinuities can occur, which means the component of the theory that addresses discontinuities must play a greater role. Given the flatter structures associated with n-ary branching, certain phenomena (e.g. inversion and shifting) do not result in discontinuities, a fact that reduces the role that the component for discontinuities must play in the theory.