Memory limitations are hidden in grammar
This challenges the assumption in linguistics that grammar can be defined independently of cognitive constraints, potentially impacting theories of human language productivity.
The study investigated whether formal grammars, which describe syntactic dependencies in language, are independent of human memory limitations by uniformly sampling sentences from possible syntactic structures. It found that average dependency distances in state-of-the-art dependency grammars are less than expected by chance, indicating memory constraints are embedded in grammatical descriptions.
The ability to produce and understand an unlimited number of different sentences is a hallmark of human language. Linguists have sought to define the essence of this generative capacity using formal grammars that describe the syntactic dependencies between constituents, independent of the computational limitations of the human brain. Here, we evaluate this independence assumption by sampling sentences uniformly from the space of possible syntactic structures. We find that the average dependency distance between syntactically related words, a proxy for memory limitations, is less than expected by chance in a collection of state-of-the-art classes of dependency grammars. Our findings indicate that memory limitations have permeated grammatical descriptions, suggesting that it may be impossible to build a parsimonious theory of human linguistic productivity independent of non-linguistic cognitive constraints.