语言学博客 Linguistic Blog

A common European starling named Sturnus Vulgaris may have the ability to recognize grammar, an ability that linguists have ascribed to humans exclusively, scientists reported on Wednesday.

The researchers from the University of Chicago and the University of California, San Diego (UCSD), show that these starlings, long known as virtuoso songbirds and expert mimics, can be trained to reliably discriminate between two different patterns of organizing the sounds they use to communicate.

These challenging findings were published in the April 27 issue of Nature.

"Our research is a refutation of the canonical position that what makes human language unique is a singular ability to comprehend these kinds of patterns," said Timothy Gentner, lead author of the study at UCSD.

"If birds can learn these patterning rules, then their use does not explain the uniqueness of human language."

The researchers focused on recursion, or center-embedding, which means creating of new and grammatically correct meanings by inserting words and clauses within sentences.

Linguists have held that recursion is universal and unique for human languages, and used rigorous rules to define the boundaries between humans and other creatures.

Previous study also suggested that even non-human primates cannot recognize anything beyond the simplest syntax. But now the researchers find that the starlings possess the most complicated linguistic ability.

Starlings produce an amazing array of complex sounds, combining chirps, warbles, trills and whistles with rattling sounds. They also have a talent for mimicry. To assess the birds' syntactical skills, the researchers exploited the diverse sounds in starling songs.

They recorded eight different 'rattles' and eight 'warbles' from a single male starling and combined them to construct a total of 16 artificial songs following two different grammars, or patterning rules.

Eight songs followed the "finite-state" rule, the simplest sort thought to account for all non-human communication. A finite-state grammar allows for sounds to be appended only at the beginning or end of a string.

The other eight songs followed the "context-free" rule, which allows for sounds to be inserted in the middle of an acoustic string, the simplest form of recursive center-embedding.

Eleven adult birds were given lessons on distinguishing between these two sets of songs using classic reinforcement techniques. The birds were rewarded with food when they heard a song from the context-free set and for refraining when they heard one from the finite-state set.

After 10,000 to 50,000 trials over several months, nine of the tested starlings learned to distinguish the patterns. /此乃经典行为主义的训练模式之胜利！

The birds were not simply memorizing particular sequences of rattles and warbles, they could distinguish between different patterns even when presented with entirely new sequences of rattles and warbles. They were applying rules to solve the task, the researchers said.

When they heard the "ungrammatical" strings -- songs that violated the established rules, the starlings treated these differently.

And remarkably, after learning the patterns with shorter songs made up of two pairs of rattles and warbles, the birds were able to recognize strings containing 6-to-8 song elements.

The finding that starlings can grasp these grammatical rules shows that other animals share basic levels of pattern recognition with humans, according to the researchers.

"There might be no single property or processing capacity," they wrote in the Nature paper, "That marks the many ways in which the complexity and detail of human language differs from non-human communication systems."

"It may be more useful," they added, "to consider species differences as quantitative rather than qualitative distinctions in cognitive mechanisms."

Source: Xinhua