Letter | Published:

Recursive syntactic pattern learning by songbirds

Abstract

Humans regularly produce new utterances that are understood by other members of the same language community1. Linguistic theories account for this ability through the use of syntactic rules (or generative grammars) that describe the acceptable structure of utterances2. The recursive, hierarchical embedding of language units (for example, words or phrases within shorter sentences) that is part of the ability to construct new utterances minimally requires a ‘context-free’ grammar2,3 that is more complex than the ‘finite-state’ grammars thought sufficient to specify the structure of all non-human communication signals. Recent hypotheses make the central claim that the capacity for syntactic recursion forms the computational core of a uniquely human language faculty4,5. Here we show that European starlings (Sturnus vulgaris) accurately recognize acoustic patterns defined by a recursive, self-embedding, context-free grammar. They are also able to classify new patterns defined by the grammar and reliably exclude agrammatical patterns. Thus, the capacity to classify sequences from recursive, centre-embedded grammars is not uniquely human. This finding opens a new range of complex syntactic processing mechanisms to physiological investigation.

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Acknowledgements

We thank T. Brawn for help in conducting some of these experiments, and A. Henly, P. Visser and L. Kay for comments on an earlier draft. This research was supported by an NIH grant to D.M.

Author information

Correspondence to Timothy Q. Gentner.

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Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

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Supplementary Note

This file contains the Supplementary Methods, Supplementary Discussion, Supplementary Tables and Supplementary Figures. (PDF 1351 kb)

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Further reading

Figure 1: Grammatical forms.
Figure 2: Classification of grammatical pattern stimuli.
Figure 3: Generalization to new FSG and CFG sequences.
Figure 4: Agrammatical controls for alternative strategies.

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