Whether playing tricks, mimicking speech, or holding “funerals,” crows and ravens (collectively known as corvids) have captured the public’s attention due to their unexpected intelligence. Thanks to results from a new Current Biology study, our understanding of their capabilities only continues to grow, as researchers from the University of Tübingen found for the first time that crows can perform statistical reasoning. These results can help scientists better understand the evolution of intelligence (and may give us a better appreciation of what’s going on in our backyard).
Bird brains
With a population of over 27 million and counting, crows seem almost ubiquitous across the US. Their loud “caws” are hard to miss, and the tone of these cries varies depending on what the birds are communicating. Like other corvids, crows have a large brain for their size and a particularly pronounced forebrain, which is associated with statistical and analytical reasoning in humans. Thanks to these attributes, ornithologists and animal behaviorists have found crows doing various “intelligent” activities, such as using twigs as tools to extract bugs from tree bark. Some experts have even classified corvids as having the same intelligence as a 7-year-old child.
Beyond using tools, corvids can also do basic mathematical functions, like adding or subtracting. “In the scheme of the natural world, very few animals are demonstrated to possess much in the way of mathematical intelligence (beyond basic numerical discrimination)—things like numerical competence, an understanding of arithmetic, abstract thinking, and symbolic representation,” explained Dr. Kaeli Swift, a postdoctoral researcher in bird behavior at the University of Washington (she was not involved in the Current Biology study). “That several corvid species have been demonstrated to possess some of these skills makes them quite special.”
Dr. Melissa Johnston, a Humboldt Fellow at the University of Tübingen, certainly appreciated the specialness of these creatures, as she and her colleagues have been studying these animals for several years. “In our lab, it has been shown that crows have sophisticated numerical competence, demonstrate abstract thinking, and show careful consideration during decision-making,” she said. In her most recent experiment, Johnston and her team pushed these abilities to a new extreme, testing statistical reasoning.
A crows’ guide to statistical reasoning
Studies involving crows are not for the faint-hearted. “A lot of training goes into experiments such as this, as we cannot ask a crow a verbal question (the way we generally do with humans) and expect an answer,” Johnston said. “Therefore, as one would do when teaching any complex task, we start with a simple version and increase the complexity step-by-step as the subject develops their skills.”
To do this, Johnston and her team began by training two crows to peck at various images on touchscreens to earn food treats. From this simple routine of peck-then-treat, the researchers significantly raised the stakes. “We introduce the concept of probabilities, such as that not every peck to an image will result in a reward,” Johnston elaborated. “This is where the crows learn the unique pairings between the image on the screen and the likelihood of obtaining a reward.” The crows quickly learned to associate each of the images with a different reward probability.
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