Constraints on multiple center-embedding of clauses

A common view in theoretical syntax and computational linguistics holds that there are no grammatical restrictions on multiple center-em bedding of clauses. Syntax would thus be characterized by unbounded recursion. An analysis of 119 genuine multiple clausal center-embeddings from seven 'Standard Average European' languages (English, Finnish, French, German, Latin, Swedish, Danish) uncovers usage-based regularities, constraints, that run counter to these and several other widely held views, such as that any type of multiple self-embedding (of the same clause type) would be possible, or that self-embedding would be more complex than multiple center-embedding of different clause types. The maximal degree of center-embedding in written language is three. In spoken language, multiple center-embedding is practically absent. Typical center-embeddings of any degree involve relative clauses specifying the referent of the subject NP of the superordinate clause. Only postmodifying clauses, especially relative clauses and that-clauses acting as noun complements, allow central self-embedding. Double relativization of objects (The rat the cat the (log chased killed ate the malt) does not occur. These corpus-based soft constraints' suggest that full-blown recursion creating multiple clausal centerembedding is not a central design feature of language in use. Multiple centerembedding emerged with the advent of written language, with Aristotle, Cicero, and Livy in the Greek and Latin stylistic tradition of 'periodic' sentence composition.