Published: Thursday, May 23, 2024
The study shows that carrion crows are the first species to link vocalizations and quantity. Sven-Erik Arndt/Arterra/Universal Images Group via Getty Images
Before they master the art of symbolic counting, where “one” represents a single item and “two”, double that amount, toddlers go through a stage in which they verbally count. When asked to count the number of apples in a group, a child may say, “one, one one”, “one two three” or even “apple apple apple” in an early form of proto-counting. The child knows there are three apple, but is not yet able to say the number “three” in an abstract way.
Diana Liao is a post-doctoral neurobiologist at the University of Tubingen, Germany. She was inspired by this information and decided to ask an obvious question: can crows also do it? Spoiler alert! They can, according a study that was published in Science on May 23. According to the new research, carrion crows are able to control their vocalizations, and correlate the number of calls with a cue in a kind of proto-counting.
The study is a new addition to the list of cognitive abilities corvids (the family of birds that includes crows and ravens as well as magpies and jays), possess. This new study also helps in the quest to discover the evolutionary origins for humans’ mathematical abilities. Scientists can learn more about our numeracy by studying the capacities and limitations of other animals.
Popular Science reports that Jessica Cantlon is a professor at Carnegie Mellon University, who specializes in quantitative reasoning. She was not involved in the investigation of the crows. The connection between our vocal system and mathematical brain is an important part of our number-sense in humans. “When you use vocalizations in the real world, it changes the way that you think. [is the way that] She explains that humans develop a sense of counting over time. Cantlon says, “It wasn’t clear until now that any other animals could do that.”
Research has shown that animals, such as crows and chimpanzees can perform basic math, distinguish between amounts, and even conceptualize zero. The level of vocal control that humans have is the only one among all animals. Cantlon says that even other primates are “so bad” at producing human language-type vocalizations. Cantlon says that people have given up on trying to train primates to speak human language. [vocalize] “Quantitative reasoning tasks”
The “ca-cawphony” of nature is not limited to crows. In contrast to people though, scientists think most animal calls are involuntary and instinctual-programmed in at birth and elicited by external environmental cues, Liao explains. Chickadees for example, have been shown to add more “dees” syllables in their alarm calls when larger predators are present. But this trend does not necessarily mean that songbirds measure predator size by their tweets. It’s more likely that the number “dees”, or alarm calls, corresponds to how much arousal is elicited when a predator appears. Larger threats will be more alarming. Liao and her team wanted to investigate this phenomenon under a controlled environment, in which an artificial lab setup would allow them to eliminate the role instinctual fear or arousal.
The study on carrion crows was the first to show that other species, besides humans, can also link vocalizations and quantity. Girogio Vallortigara is a neuroscientist from the University of Trento, Italy. He has published research on numeracy among zebrafish and newborn chicks. He explains that tracking vocalizations requires “timing” and extensive memory. It is a very advanced cognitive ability.
Liao, along with her co-authors, trained three carrion raves to recognize colored arabic numbers (1, 2, 3 and 4), and neutral auditory clues (i.e. Sounds that were not related to natural threats or prey were paired with a flexible, corresponding series of vocalizations. Liao said that the process took a year and was mostly a result of trial and error. Researchers would show each crow a number or pre-recorded sounds on a screen and reward the bird if it made the matching number of sounds.
After training, the crows underwent repeated tests lasting between one and two hours. The birds were positioned in front a screen and pecked a target to start the trials. A number or audio cue was displayed on the screen as a response. The crows call back in response and then tap an “enter key”, on the screen, to show that they are done. The crows were rewarded with mealworms or birdseed pellets if they correctly matched the number cue.
All three crows were able to match their vocalizations much more accurately than by chance, across 20 sessions. The crows were usually right. They responded to number one with 100% accuracy, number two with more than 60%, number three with over 50%, and number four was about 40% accurate. The researchers also found, using a computer-based analysis tool, that the first call in a sequence differs significantly depending on how many calls will follow. This suggests that crows plan their response from the first caw. Researchers also assessed the trails of crows that got it wrong and found two types of errors: stutters, where birds repeat the same call, and skips, when a bird forgets to make a particular call. This suggests that birds who get it wrong usually start out with the right plan and lose track as they go.
The experiments show that carrion crows are able to respond to random cues by making or not making vocalizations. They also count aloud, just like toddlers.
The study has some limitations, however. Liao says that the authors did not measure arousal, but it may still have played a role in the birds’ responses. Cantlon says that it is possible the birds are tracking call duration and not discrete syllables in their responses. In that case, the birds may not be able to make a direct connection between a particular call and an object. They could simply associate the length of time of the stimulus with the duration of the call. To be sure, further research is needed.
Liao hopes to explore the brain systems that support the newly discovered vocalization ability. He also plans to do additional experiments to see how crows use this capability in the wild. “The avian and primate lines diverged over 300 million years back. We have evolved brain architectures that are dramatically different. “It would be fascinating to see how brains can produce similar behaviors.”
What we learn from crows today could help us understand ourselves in the future. Cantlon says that mathematics is “a defining characteristic” of the human mind, but it’s not like we have invented a completely new way of thinking. We can see that modern species have a history behind everything they do. We can trace our thinking history by looking at the different branches of the evolution tree.