Whether they are playing tricks, imitating speech or holding "funerals", crows attract the public's attention with their unexpected wisdom. Researchers at the University of Tübingen have discovered for the first time that crows are capable of statistical reasoning. These results could help scientists better understand the evolution of intelligence (and possibly give us a better idea of what's going on in our backyards).
With a population of over 27 million, crows are almost everywhere in the United States. Their loud "calls" are hard to ignore, and the pitch of these calls varies depending on the message the bird is trying to convey. Like other corvids, crows have large brains with particularly pronounced forebrains, which are related to human statistical and analytical reasoning abilities. Thanks to these properties, ornithologists and animal behaviorists have discovered that crows perform a variety of "intelligent" activities, such as using branches as tools to extract bugs from tree bark. Some experts even believe that crows have the same intelligence as a 7-year-old child.
In addition to using tools, corvids can perform basic mathematical operations such as addition and subtraction. "Few animals in nature have been shown to possess substantial amounts of mathematical intelligence (beyond basic numerical discrimination)—such as numerical ability, understanding of arithmetic, abstract thinking, and symbolic representation," explained Dr. Kelly Swift, a postdoctoral researcher in avian ethology at the University of Washington. "Several species of corvids have been shown to possess some of these skills, which makes them quite special."
Dr. Melissa Johnston, a Humboldt researcher at the University of Tübingen, certainly appreciates the special nature of these animals because she and her colleagues have been studying them for several years. "Our lab has demonstrated that crows have complex computational abilities, exhibit abstract thinking, and exhibit deliberation in their decision-making processes," she said. In recent experiments, Johnston and her team took these abilities to a new extreme, testing statistical reasoning abilities.
Research involving crows is not for the faint of heart. "It takes a lot of training to do an experiment like this because we can't ask a crow a verbal question (like we typically ask humans) and expect the crow to give an answer," Johnston said. "So, like teaching any complex task, we start with simple tasks and then gradually increase the complexity as the subject's skills improve."
To do this, Johnston and her team first trained two crows to peck at various images on a touch screen in order to obtain food. Starting from this simple "pecking first, then eating" routine, the researchers greatly increased the difficulty of the training. "We introduced the concept of probability, such that not every peck on the image will result in a reward," Johnston elaborated. "This is where the crows learn the unique pairing between the images on the screen and the likelihood of receiving a reward. As a result, the crows quickly learn to associate each image with a different probability of reward."
In the experiment, two crows had to choose between two images, each corresponding to a different probability of reward. "The crows' task was to learn fairly abstract quantities (i.e., non-integers), associate them with abstract symbols, and then apply this combination of information in a reward-maximizing way," Johnston said. "After 10 days of training and 5,000 trials, the researchers found that both crows continued to choose the crow with the higher probability of reward, demonstrating their ability to use statistical reasoning."
Statistical reasoning is the use of limited information about a situation to draw conclusions and make decisions. People use statistical reasoning every day without even realizing it, such as when deciding which cafe has more seats for a group of friends. Johnston added: "You only have time to go to one cafe, so you might think back to cafes you've been to before and conclude that there are (relatively) more seats available in cafe A than in cafe B, so you choose to go to cafe A. In either case, you're not guaranteed a seat, but one is considered the better choice. Likewise, crows remember the link between the image on the touch screen and the probability of reward, and use this memory to ensure they get the highest reward most of the time."
To further stimulate the crows, Johnston and her team waited a full month before testing them again. Even after a month of no training, crows were able to memorize reward probabilities and pick the highest number every time. Crows can use statistical reasoning to secure rewards in almost any situation, which excites Johnston and her team. "Working with these birds every day is so rewarding! They are very responsive animals, so I enjoy my time with them," Johnston added.
Crows are one of the few animals that have successfully adapted to urbanization, no doubt thanks to their intelligence. These birds often use man-made structures such as tunnels as places to stay warm during the winter. These behaviors are why urban ecologists classify corvids as "exploiters" because they not only tolerate humans but actually thrive in urban environments. As Johnston and her team discovered, part of this exploitative behavior may be due to the birds' ability to use statistical reasoning. Johnson added: "Wild crows may use statistical inference in their ecological behavior; although I suspect they have crow cafes, they visit a variety of sites associated with varying degrees of foraging success."
As research further reveals the intelligence of crows, public perceptions of these birds continue to change. Historically, crows have symbolized death. In the West, crows are viewed with a mixture of admiration and hostility. "Many people desire a relationship with crows, while others view them as pests and look forward to the opportunity to control them."
Thankfully, these animals are protected under the Migratory Bird Treaty Act. The law doesn't stop some states from selling crow hunting licenses at certain times of the year, though. "There are still a lot of people who will happily get their annual crow license and shoot hundreds of crows for fun," Swift noted.
Increasingly, though, the public is beginning to appreciate the intelligence of these animals. From neighborhood crow social media channels to sports team mascots to important studies like this one, crows are increasingly viewed as attractive and approachable. "I think, for a lot of people, these studies allow them to appreciate crows in a way they didn't before," Swift said. "They may start to pay more active attention to crows because they realize they might be doing some fun and exciting things, like playing. I think these studies could help improve our relationship with urban crows and change what crows symbolize to us."