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Maybe “birdbrained” isn’t such an insult after all – crows, ubiquitous city birds, can count up to four out loud, new research has found.
According to a new study led by a team of researchers from the Laboratory of Animal Physiology at the University of Tübingen in Germany, the inquisitive creatures can not only count, but can also match the number of calls they make when shown a number.
The way birds recognize and respond to numbers is similar to the process we humans use to learn to count as toddlers and quickly recognize how many objects we are looking at. The findings, published Thursday in the journal Science, add to our growing understanding of crow intelligence.
“Humans do not have a monopoly on skills such as numerical thinking, abstraction, tool making and planning ahead,” animal cognition expert Heather Williams said by email. “It shouldn’t surprise anyone that crows are ‘smart.'” Williams, a biology professor at Williams College in Massachusetts, was not involved in the study.
In the animal kingdom, counting is not limited to crows. Chimpanzees learned to count in numerical order and understand the value of digits, much like young children. When some male frogs are trying to court mates, they count the number of calls from competing males to match, or even increase that number when it’s their turn to croak at the female. Scientists have even theorized that ants trace their paths back to their colonies by counting their steps, although this method is not always accurate.
This latest study showed that crows, like young people, can learn to associate numbers with values—and count aloud accordingly.
The research was inspired by toddlers learning to count, said study lead author Diana Liao, a neurobiologist and lead researcher at the Tübingen lab. Toddlers use number words to count the number of objects in front of them: If they see three toys in front of them, their counting might sound like “one, two, three” or “one, one, one.”
Perhaps crows could do the same, Liao thought. She was also inspired by a June 2005 study of chickadees that adapted their alarm calls to the size of a predator. The study found that the greater the wingspan or body length of the predator, the fewer “dee” sounds chickadees used in their alarm call. The opposite was true for smaller predators — songbirds would use more “dee” sounds if they encountered a smaller bird, which could be more of a threat to chickadees because they are more agile, Liao said.
The authors of the chickadee study could not confirm whether the little songbirds had control over the number of sounds they made or whether the number of sounds was an involuntary response. But the possibility piqued Liao’s curiosity—could crows, whose intelligence has been well documented over decades of research, demonstrate control over their ability to produce a certain number of sounds and effectively “count” like toddlers?
Liao and her colleagues trained three carrion crows, a European species closely related to the American crow, in more than 160 sessions. During training, the birds had to learn associations between a series of visual and auditory stimuli from 1 to 4 and produce the corresponding number of cows. In an example provided by the researchers, a visual cue might look like a bright blue number, and its corresponding sound might be a half-second drum song.
The crows were expected to perform the same number of caws as the number represented by the cue—three caws for the number 3 cue—within 10 s of seeing and hearing the cue. When the birds stopped counting and clucking, they pecked at the “enter” key on the touch screen that represented their cues to confirm they were done. If the birds counted correctly, they would get a treat.
As the cues continued, the crows seemed to take longer to respond to each cue. Their reaction times increased as “more vocalizations came in,” Liao wrote, suggesting that the crows were planning the number of caws they would make before opening their beaks.
The researchers could even tell how many calls the birds planned to make based on how their first call sounded—subtle acoustic differences that showed the crows knew how many numbers they were looking at and synthesized the information.
“They understand abstract numbers … and then they plan ahead how they’re going to adjust their behavior to match that number,” Williams said.
Even the mistakes the crows made were somewhat advanced: If the crows crowed too many times, stuttered the same number, or answered prematurely with their beaks, Liao and her researchers could tell where they were going by the sound of the first call. poorly. These are “the same kinds of mistakes that people make,” Williams said.
Previously, birds and many other animals were thought to make on-the-spot decisions based on cues in their immediate environment, a theory popularized by 20th-century animal behaviorist BF Skinner. But the latest research by Liao and her colleagues provides more evidence of crows’ ability to synthesize numbers to make sound, and suggests that they are in control of this skill.
The study team’s findings are highly specific but still significant — challenging the once-held belief that all animals are merely stimulus-responsive machines, said Kevin McGowan, a researcher at the Cornell Lab of Ornithology in Ithaca, New York, who spent more of the money. have been studying wild crows in their habitats for over two decades. McGowan was not involved in the study.
The study, McGowan told CNN, showed that “crows are not just simple unthinking machines responding to their environment — they actually think ahead and have the ability to communicate in a structured, pre-planned way. It’s kind of a necessary precursor to having a language.’
Crow intelligence has been studied for decades. Scientists have studied how New Caledonian crows create their own compound tools to access food. The birds seem to make the rules, according to a November 2013 study co-authored by University of Tübingen Laboratory Principal Investigator Andreas Nieder. The crow’s tongue has also puzzled scientists for decades with its very different tones and expressions, McGowan said.
Nor is the study by Liao and her colleagues the first to consider whether crows can count. This research was started by Nicholas Thompson in 1968, noted animal cognition expert Irene Pepperberg. A research professor of psychology and brain sciences at Boston University, Pepperberg is best known for her work with an African gray parrot named Alex.
Thompson hypothesized that crows can count based on their caws, the duration and number of which the birds seem to control in a given burst of sound. The computational abilities of crows “appear to exceed the demands placed on such abilities by survival,” he wrote.
Another University of Tübingen study on crows’ counting abilities from September 2015 trained the birds to recognize clusters of dots and recorded the activity of neurons in the part of the crows’ brain that receives and makes sense of visual stimuli. The researchers found that crow neurons “ignore the size, shape and arrangement of the dots and only extract their number,” the university said in a statement at the time.
“So the crow’s brain can represent different quantities, and crows can quickly learn to match those quantities with Arabic numerals — something that humans usually explicitly teach their children,” Williams said.