Elsevier

Consciousness and Cognition

Volume 26, May 2014, Pages 169-188
Consciousness and Cognition

Is recursion language-specific? Evidence of recursive mechanisms in the structure of intentional action

https://doi.org/10.1016/j.concog.2014.03.010Get rights and content

Highlights

  • Recursion has been hypothesized to be language-specific.

  • We identify the formal features of recursion in the domain of intentional action.

  • We review evidence that linguistic recursion might be embodied in motor processing.

  • We review evidence that linguistic and motor-intentional recursions might be double dissociated.

  • We conclude that recursion is not language-specific.

Abstract

In their 2002 seminal paper Hauser, Chomsky and Fitch hypothesize that recursion is the only human-specific and language-specific mechanism of the faculty of language. While debate focused primarily on the meaning of recursion in the hypothesis and on the human-specific and syntax-specific character of recursion, the present work focuses on the claim that recursion is language-specific. We argue that there are recursive structures in the domain of motor intentionality by way of extending John R. Searle’s analysis of intentional action. We then discuss evidence from cognitive science and neuroscience supporting the claim that motor-intentional recursion is language-independent and suggest some explanatory hypotheses: (1) linguistic recursion is embodied in sensory-motor processing; (2) linguistic and motor-intentional recursions are distinct and mutually independent mechanisms. Finally, we propose some reflections about the epistemic status of HCF as presenting an empirically falsifiable hypothesis, and on the possibility of testing recursion in different cognitive domains.

Introduction

In their seminal work Hauser, Chomsky, and Fitch (2002) argued that linguistic, syntactic recursion can be considered as the only constitutive feature of the faculty of language in the narrow sense. In other words, even though the faculty of language “broad sense” (FLB) also includes a phonological system based on the operations of the sensory-motor apparatus, and a conceptual-intentional system conferring meaning to syntactically structured representations, syntactic recursion is the only component of the faculty of language “narrow sense” (FLN).

More specifically, HCF’s hypothesis is that FLB – the set of syntactic, conceptual and phonological mechanisms constituting the faculty of language as a whole – includes mechanisms shared by language with other cognitive skills and shared by humans with other species. FLN, on the contrary, is composed only by “the core mechanisms of recursion as they appear in narrow syntax and the mappings to the interfaces”, which are “recently evolved”, “unique to our species” and “quite specific to FLN” (HCF, 2002, p. 1573). Recursion and the interfaces allowing interaction with the conceptual-intentional system (responsible for semantics and pragmatics, cf. Fitch, Hauser, & Chomsky, 2005, p. 182) and with the sensory-motor, phonological system might be the features differentiating human cognition from non-human animals and the faculty of language from the rest of our cognitive skills. Language essentially is, according to HCF, a system of sound-meaning connections endowed with a core syntactic recursive component enabling the construction of an infinite number of discrete expressions starting from a finite number of primitive elements.

The authors regard this hypothesis as providing a multidisciplinary conceptual framework, or research program (Brattico, 2010), able to analyze not only language but also, more generally, human creativity. The idea is that a recursive syntactic engine emerged in a cognitive economy that already included a phonological system and a conceptual system. The phonological and conceptual systems causally bond the syntactic system by way of imposing “legibility conditions”: syntactic structures, for example, must be able to express a conceptually valid meaning in a phonologically structurable format (Chomsky, 2000). But recursion allows the previously existing conceptual thought to go beyond the narrow scope of the sensory-motor horizon of the here and now through discrete infinity (Fitch, 2010, cf. Brattico, 2010).

HCF’s hypothesis has been criticized in different ways: there is evidence of the ability to discriminate recursive strings in non-human animals (Abe and Watanabe, 2011, Corballis, 2007, Gentner et al., 2006; cf. Bloomfield et al., 2011, van Heijningen et al., 2009) and there are non-syntactic (i.e., phonological, cf. Schreuder, Gilbers, & Quené, 2009) recursive structures in language. Relatively little work has been done, on the contrary, to test the claim that recursion is “quite specific to FLN” – that is, that recursion is language-specific.

In this work we will focus on this latter claim. We will argue that there are sensory-motor recursive structures in the domain of intentional action – that is, at the sensory-motor level that mediates our fundamental interactions with the environment. To this aim, we will first sketch the core concepts of HCF and current objections against it in order to clarify the target of the investigation: what is “recursion”? What are its central properties? What does it mean that they are “quite specific to FLN”? We will then introduce John R. Searle’s (1983) analysis of the intentionality of action, which characterizes intentions as logically and biologically primitive mental representations with a causally self-referential (and, therefore, self-embedding) logical structure which cannot be reduced to the logical structure of beliefs and desires (Searle, 1983, p. 36). On the grounds of this analysis, we will then argue that the specific features of recursion (self-embedding, long-distance dependence, identity preservation, discrete infinity) might be already present in the structure of the sensory-motor system. We will then review evidence from cognitive science and neuroscience to support the claim that motor-intentional recursion is language-independent. We will distinguish two explanatory hypotheses. According to the first hypothesis, linguistic recursion is embodied in sensory-motor processing: the available evidence allows us to hypothesize that HCF’s causal-evolutionary route might be taken the other way round, identifying in sensory-motor processing the roots of linguistic recursion. According to the second hypothesis, linguistic and motor-intentional recursions might be independent mechanisms, realized in distinct neural circuits, that can be (and in some cases are) double dissociated.

Finally, we will propose some reflections about the epistemic status of HCF as presenting an empirically falsifiable hypothesis, and on the possibility of testing recursion in different cognitive domains.

Section snippets

Recursion as the core of the faculty of language

Despite the pivotal role of recursion in HCF in explaining the evolution and uniqueness of language, both the original paper and the answer to the objections raised by Pinker and Jackendoff (2005, cf. Fitch et al., 2005) have very little to say about what the authors mean by “recursion” or about the reasons for regarding this mechanism as language-specific.

In HCF recursion is characterized just as “a core property of FLN” attributed to “narrow syntax”, that is “a computational mechanism […]

Recursion outside language: some potential counterexamples to HCF

Debate after HCF focused mainly on the issue of what is “recursion” and on whether recursion is human-specific and FLN-specific. By comparison, relatively little work has been done on the claim that recursion is language-specific.

Recursion and the logical structure of intentional action

Our hypothesis is that John R. Searle’s (1983) philosophical analysis of the intentionality of acting and perceiving can be extended to capture the presence of the crucial features of recursion (self-embedding, long-distance dependence, identity preservation, discrete infinity) in sensory-motor processing. Intentionality is, in philosophical jargon, a property of mental states in virtue of which some of them (such as beliefs, desires, hopes, fears, and intentions) are directed to, refer to, or

How many recursions? Disentangling the relationship between action and language

In the last paragraph we have discussed our hypothesis of recursive processes and structures in the domain of intentional action. Even assuming that this hypothesis is correct, a question remains: what are the relationships between linguistic recursion and recursion in the structure of intentional action? Adopting a Chomskyan perspective the answer seems reasonably predictable: since recursion is language-specific, then recursion in non-linguistic domains must be language-dependent. Therefore

Conclusion

In this paper we examined the issue of whether recursion is language-specific starting from HCF’s hypothesis that recursion is the only constitutive mechanism of the faculty of language.

The analysis of the structure of intentional action has led us to hypothesize the presence of recursive mechanisms at the level of motor intentionality. Intentions (both simple intentions-in-action and complex prior intentions) are satisfied if and only if the corresponding action is realized in a specific way

Acknowledgments

Research on the topics of this paper has been made as part of GV’s research projects on “Embodied, Embedded Mind and the Challenges of Subjectivity: Theoretical Perspectives and Historical-Philosophical Perspectives”, (Post-doctoral research funds, MIUR 2009, University of Palermo) and “The ecological and embodied bases of recursion” (PhD course in neuroscience, University of Turin). MA was supported by MIUR of Italy (FIRB 2012, RBFR12FOBD_001) and by the University of Turin (Ricerca

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