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.

Even within the same Ph.D. programs, adaptationists were at least as liberal as their non-
adaptationist graduate student colleagues. There were no significant group differences between
adaptationists and non-adaptationists with respect to political party identification, presidential
candidate preference, or two of the three political attitudes factors. The only exception was that,
contrary to the ARC hypothesis, adaptationists were more liberal than non-adaptationists on
beliefs regarding individual rights, even after removing a potentially biasing religion item.

We thus demonstrate that starlings can recognize syntactically well-formed strings, including those that use a recursive centre-embedding rule. At least a simple level of recursive syntactic pattern processing is therefore shared with other animals. These results challenge the recent claim that recursion forms the computational core of a uniquely human narrow faculty for language (FLN)4. We attempted to rule out the most plausible finite-state solution strategies that could account for accurate classification of A n B n patterns (Supplementary Information), suggesting that the learned patterning rule conforms to a stochastic context-free grammar. In practice, however, the stimulus sets used to test such claims must be finite. Thus, the theoretical possibility remains that a finite-state grammar, however heavily contrived, may account for the observed behaviour (see Supplementary Information). Of course, theoretical difficulties in proving the use of context-free rather than finite-state grammars extend to studies of grammatical competence in humans as well, and therefore call into question the falsifiability of claims regarding CFGs in humans compared to non-humans.

Although uniquely human syntactic processing capabilities, if any, may reflect more complex context-free grammars or higher levels in the Chomsky grammatical hierarchy, it may prove more useful to consider species differences as quantitative rather than qualitative distinctions in cognitive mechanisms. Such mechanisms (for example, memory capacity) need not map precisely onto strict formal grammars and automata theories. There might be no single property or processing capacity that marks the many ways in which the complexity and detail of human language differs from non-human communication systems13. Future studies can gauge the extent of the recursive syntactic abilities demonstrated here, by examining the
processing of right-embedded structures more common in human languages (and more easily understood), and the interface between generalized syntactic and semantic knowledge.

Fideikommiss är en feodal kvarleva som inte hör hemma i en folkstyrd demokrati som Sverige. Att svensk arvslagsstiftning inte gäller för de största gods- och markägarna i Sverige är ju helt barockt och inte förenligt med ett modernt tänkande om alla människors lika värde. Äldste sonen bör rimligtvis inte få ärva allt. Därför bör en socialdemokratisk regering när den kommer till makten arbeta för att avskaffa denna möjlighet i lagstiftningen och ersätta den med samma regler och lagar som gäller för övriga medborgare.