Syntactic recursion and iteration

The nature and origin of syntactic recursion in natural languages is a topical problem. Important recent contributions include those of Johansson (2005), Parker (2006), Tomalin (2006; 2007), and Heine and Kuteva (2007). Syntactic recursion will here be discussed especially in relation to its cognate concept of iteration. Their basic common feature is plain structural repetition: “keep on emitting instances of the current structure, or stop”. Their main difference is that recursion builds structure by increasing embedding depth whereas iteration yields flat output structures which do not increase depth. My focus here is on the types of recursion and iteration, and on what empirically determinable constraints there are on the number of recursive and iterative cycles of application. Recursion comes in two subtypes, nested recursion (= center-embedding) and tail-recursion, the latter covering left-recursion and right-recursion. There are six functionally different types of iteration: structural iteration, apposition, reduplication, repetition, listing and succession. It will be empirically shown that multiple nested syntactic recursion of degrees greater than 3 does not exist in written language, neither in sentences nor in noun phrases or prepositional phrases. In practice, even nesting of degree 2 is extremely rare in writing. In speech, nested recursion at depths greater than 1 is practically non-existing, thus partly confirming an early hypothesis of Reich (1969). Left-branching tail-recursion of clauses is strictly constrained to maximally two recursive cycles. Right-branching clausal tail-recursion rarely transcends three cycles in spoken language and five in written language. On constituent level both leftand right-branching is less constrained (especially in written language), but e.g. left-branching genitives rarely recurse more than two cycles ([[[Pam’s] mum’s] baggage]).