In the April 27, 2006, issue of Nature, the researchers 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.
"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, assistant professor of psychology at UCSD and lead author of the study. "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, a characteristic, found in all human languages. Recursion is one way of creating of new and grammatically correct meanings by inserting words and clauses within sentences -- theoretically, without limit. So, for example, "The bird sang," can become "The bird the cat chased sang."
Following the lead of language theorist Noam Chomsky, linguists have held that this recursive center-embedding is a universal feature of human language and, moreover, that the ability to process it forms a unique computational ability important for human language.
"Linguists have developed a mathematically rigorous set of definitions, a hierarchy of syntactical complexity, that governs the process of how humans create and understand utterances," said Daniel Margoliash, professor of anatomy and organismal biology at the University of Chicago and co-author of the study. "These rules govern how to properly express yourself – how to structure your phrases and sentences.
Language experts have used properties of these rules, whose complexity is described by the Chomsky hierarchy, "to define the boundaries between humans and other creatures," said Margoliash. "Now we find that we have been joined on this side of that boundary by the starling. It should no longer be considered an insult to be called a bird brain."
Although they are not known for the lilting beauty of their songs, starlings produce an amazing array of complex sounds, combining chirps, warbles, trills and whistles with rattling sounds.
They also have a talent for mimicry. One starling famously copied an unpublished tune that Mozart whistled in a pet store; the composer purchased the bird and kept it as a pet. The starling is mentioned only once in all of Shakespeare, but in that passage an angry warrior, forbidden by the King to speak of a rival, Mortimer, decides he will "have a starling shall be taught to speak nothing but ’Mortimer,’ and give it him to keep his anger still in motion." (Because of this passage, 100 European starlings were first introduced to New York City’s Central Park in the 1890s. They flourished. North America now has an estimated 200 million starlings.)
One previous study, however, suggested that even non-human primates are incapable of recognizing anything beyond the simplest syntax. A paper published in Science in 2004 by scientists at Harvard and MIT found that cotton-top tamarin monkeys were not able to master higher-level grammar patterns. "The acquisition of hierarchical processing ability," the authors of that paper conclude, "may have represented a critical juncture in the evolution of the human language faculty." They also noted that vocal learners, such as songbirds, might have produced different results.
"When I saw that study I was not convinced of the significance of the failure of the monkeys," said Howard Nusbaum, chairman and professor of psychology at the University of Chicago and senior author of the Nature study. "There are many ways for an experiment to fail and most failures are not scientifically interesting. I immediately thought: we could do that in starlings."
Nusbaum, Margoliash and psychologist Kimberly Fenn had previously collaborated on studies of the role of sleep in speech perceptual learning. Gentner, a neuropsychologist, expert on starlings and, at the time, a postdoctoral fellow at the University of Chicago, was an essential addition.
To assess the birds’ syntactical skills, the research team 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. These songs followed 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. These songs were built up from a rattle-warble base by adding rattle-warble pairs at the end. The simplest song (ab) was one rattle followed by one warble. The next simplest a rattle, then a warble, followed by a different Rattle and Warble (abAB).
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. So a context-free sequence also began with rattle-warble base (ab) but built up by inserting new sounds in the middle, such as rattle-Rattle-Warble-warble (aABb).
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, 9 of 11 tested starlings learned to distinguish the patterns. 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 also checked to see how the birds responded to "ungrammatical" strings, songs that violated the established rules. The starlings treated these differently, as expected if they had learned the patterns.
The experimenters then asked if the birds were capable of a key feature of human grammars. Could the starlings extrapolate these patterning rules to distinguish among longer strings? 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 (abababab – vs – aaaabbbb).
The finding that starlings can grasp these grammatical rules shows that other animals share basic levels of pattern recognition with humans. "There might be no single property or processing capacity," the authors write, "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 add, "to consider species differences as quantitative rather than qualitative distinctions in cognitive mechanisms."
"The more closely we understand what non-human animals are capable of," Gentner said, "the richer our world becomes. Fifty years ago, it was taboo to even talk about animal cognition. Now, no one doubts that animals have complex and vibrant mental lives."
"When I describe our results to linguists and psycholinguists, they are amazed," Nusbaum said. "When I mention them to people who study animal behavior," Margoliash countered, "they are not surprised. They are well aware of the cognitive abilities of many animals."
"These birds are a lot smarter than you might think," Margoliash said. "They have innate abilities. They solve interesting problems and learn difficult tasks. Any number of times during the experiments I said ’they can’t possibly do that,’ and they did."
"There has long been a temptation," writes cognitive neuroscientist Gary Marcus of New York University in a commentary, "to sum up the differences between human and other species in a neat turn of phrase – but most posited differences turn out to have been overstated."
But these iridescent six-inch, three-ounce singing black birds have known this all their lives. They were only waiting for this moment to arise.
John Easton | EurekAlert!
Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel
Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences