Prosody as a recursive embedding tool in production and perception of Karaja: an acoustic and neuro-psycholinguistic investigation

Hierarchical or indirect recursion can be found in different domains of human language and thus, it has been claimed to be the only part of language that is specific to humans (Hauser, Chomsky, and Fitch 2002). However, in the past decade, both the claims that, recursion is the central component of the “narrow faculty of language” and that, it should be present in all languages have been the object of intense debate (cf. Pinker & Jackendoff, 2005; Everett, 2005). This debate triggered the exploration of new frontiers in the examination of embedded structures, which have been examined in acquisition and in processing and have been shown to be implemented through a wide array of linguistic resources in different languages. This paper presents an acoustic description and a neuro-psycholinguistic analysis (ERP/EEG) of an uncommon cognitive device to embed relative clauses. It is implemented in Karaja, a Macro-Je language spoken in Central Brazil, which uses stress shift in relativization: (i) [tori do’rode] ‘the white man arrived’ versus (ii) [tori doro’de] ‘the white man who arrived’, as first described in Ribeiro (2006). The major interest in studying this phenomenon is because in Karaja, more than structuring envelopes for acts of speech, prosody codes directly onto the central syntactic algorithm of recursion. We found evidence in favor of a stronger facilitation to process a coordinated structure than a recursive structure. We found smaller RTs and amplitudes in the EEG related to the coordinated conditions versus the embedding conditions. Also, it seems that even though embedding is harder to launch, hierarchical structuring makes it easier to process in the third embedding, when comprehenders learn they are in an embedding mode. Coordination, on the other hand, being a default, is easier to launch, but it seems to become progressively harder as it does not benefit from hierarchical structuring.