Hauser, Chomsky and Fitch 2002 (HC&F hereafter) incited a flurry of discussion in response to its distinction between the faculty of language in the broad sense (FLB) and the faculty of language in the narrow sense (FLN): “FLB includes a sensory-motor system, a conceptual-intentional system, and the computational mechanisms for recursion, providing the capacity to generate an infinite range of expressions from a finite set of elements. We hypothesize that FLN only includes recursion and is the only uniquely human component of the faculty of language.” (HC&F, 1569). The implication is that the observable structural differences between human language and other forms of animal communication can be explained by the exclusivity of recursion to human language. This statement also operates on the assumption that recursion is a universal trait of human language.
Image courtesy of this site.
Daniel Everett’s work with the Pirahã tribe in the Amazon presents evidence contrary to HC&F’s claims. Everett found that the Pirahã language lacked embedding, at least representational recursion1: “Pirahã does not make use of CP-embedding or recursive possessors.” (Kinsella 2010: 188)2 Nonetheless, they can, through other linguistic and pragmatic means, express concepts which in other languages would be expressed recursively (ibid.). Everett says “..Pirahã most certainly has the communicative resources to expresses clauses that in other languages are embedded…” (Everett 2005: 631) Therefore, though Pirahã does not seem to have recursion, it is by no means restricted in its expressive capacity, countering the claims of Hauser, Chomsky and Finch 2002 regarding “the rich expressive and open-ended power of human language (based on humans’ capacity for recursion),” which capacity they claim animal communication lacks because it does not exhibit recursion (HC&F, 1570). If Pirahã’s expressive capacity is not hindered by its seeming lack of recursion, then perhaps recursion is not in fact a distinguishing feature of human language (Kinsella 188), or at least not the only one: perhaps it can be found in non-linguistic and non-human domains.
Image courtesy of HC&F 2002.
This may in fact the case. HC&F 2002 themselves speculate that recursion may be evident in animal navigation and kinship cognition, and songbirds have exhibited the capacity to comprehend recursive hierarchical syntactic structure (Abe & Watanabe 2011; Gentner et al 2006). Bengalese finches exposed to an artificially-constructed, center-embedded birdsong grammar “revealed a striking sensitivity to the recursive structure of the grammatical strings [they] were exposed to.” (Bloomfield et al 2011) The finches responded equally to familiar and novel grammatical strings, but decreased in response when presented with ungrammatical birdsong strings (ibid.). This indicates that recursion is not necessarily specific to humans, and that it is only sufficient, not necessary for human language, as Everett’s work with the Pirahã indicates. Therefore, since recursion as a unique feature of language is questionable, it would be fruitful to comparatively investigate the other possibly-distinguishing properties of language— the syntax-semantics interface particularly, as well as the lexicon and the nature of phrasal categories (Kinsella 2010).