Corvus corone: the carrion crow. Credit: Wikimedia Commons Two crows named Iggy and Lemmy have just beaten humans in a game of mental speed. Their task was simple: look at a screen full of moving dots and figure out which direction they were going. The crows made their decisions in less than a quarter of a second, about twice as fast as humans and other primates in comparable experiments. And they weren’t just guessing. Now, scientists have looked inside their brains to find out how. What they discovered is surprising: Despite having brains built very differently from ours, crows appear to use remarkably similar neural machinery to make decisions. But they are faster than us. The fastest brains in the laboratory At the University of Tübingen, Germany, neuroscientists Philipp Schmidbauer and Andreas Nieder trained two carrion crows, Iggy and Lemmy, to inspect a cloud of white dots on a touch screen. Some traveled together left, right, up or down. Others wandered around at random. The birds had to identify the general direction and peck the appropriate target to receive a mealworm reward. The dot experiment. There are two photographs of the animals provided by the authors, but I found no clarification as to which bird is which. So I’ll assume this is Iggy (looks like an Iggy). Credit: Andreas Nieder The researchers could make the challenge easier or harder by changing how many dots moved in the same direction. When almost all the points traveled together, the answer was obvious and the Ravens got it right virtually every time. But when only a handful moved together amid a sea of randomly moving dots, detecting the pattern became much more difficult. Even then, both birds identified the correct direction more often than they would have done by guessing. Even when only 3% of the dots moved together, both birds performed better than chance. ×Thank you! One more thing… Please check your inbox and confirm your subscription. The researchers performed thousands of tests and each bird took only about 235 milliseconds (0.2 seconds) to initiate its response. The researchers measured when each bird started turning its head, not when its beak hit the screen. Illustration: ZME Science. To put that speed into perspective, the researchers compared their results to six previous studies with monkeys and humans. In their analysis, it took monkeys approximately 410 to 600 milliseconds to make similar visual decisions, while humans took 450 to 820 milliseconds. The crows, by contrast, responded in just 235 milliseconds on average. So how does a crow’s brain come to a decision so quickly? A different brain, a familiar calculation And this must be Lemmy. Credit: Andreas Nieder The big surprise came from electrodes that recorded the activity of 248 nerve cells in the birds’ nidopallium caudolaterale, a region involved in planning and decision-making, roughly the equivalent of the prefrontal cortex of mammals. Of those cells, 58 responded differently depending on which direction the crow chose. About 70 milliseconds after the dots appeared, their activity began to predict the decision. As the crows weighed the visual cues, these neurons fired more rapidly, reaching a similar level of activity just before each bird made its choice. As the birds collected visual evidence, the activity of these neurons increased. Stronger evidence produced a steeper increase. By the time the crows began to respond, the signals had converged to a similar level. This resembles a process scientists previously documented in monkeys: The brain gradually weighs visual evidence, and certain neurons become increasingly active until the animal commits to making a decision. Think of it as a neural count. Each new piece of evidence brings the brain closer to making a decision. Surprisingly, the neural signals also predicted the crows’ choices when the dots moved completely randomly, and even when the birds chose incorrectly. The cells seemed to reflect the decision itself, not just the stimulus. This is where things get really interesting. Bird Brain Although birds and mammals share some basic brain structures, their brains have diverged onto very different paths over more than 360 million years. In mammals, much of our complex thinking takes place in the neocortex, whose neurons are arranged in six distinct layers. Birds lack this layered structure, but do possess a corresponding region of the forebrain called the pallium, where nerve cells are largely organized in groups. Despite these anatomical differences, the new findings suggest that both brains use remarkably similar neural processes to make decisions. “It’s not about architecture,” Mike Colombo, a neuroscientist at the University of Otago in New Zealand, who was not involved in the study, told NPR. “What matters are the circuits, and they are the same circuits.” Skills problem? So why were crows so fast? Scientists don’t know yet. But there are some intriguing possibilities. The crow’s brain is small and densely wired. A 2016 study of bird brains found that songbirds and parrots contain about twice as many neurons in the same brain mass as primates. Such compact cabling can offer a speed advantage: shorter connections mean signals have to travel less distance. “Long queues take time. Short queues speed everything up,” Nieder told Ars Technica. Temperature can also play a role. Many birds maintain a body temperature of around 41° or 42° Celsius, warmer than humans, which could speed up chemical processes underlying nerve signaling. Evolution may also have favored rapid visual processing in animals that must navigate in flight, detect predators, and guide their beaks precisely. Then there’s the matter of being a bird. Flying through cluttered environments, dodging obstacles, and precisely guiding a beak toward food requires exceptionally fast visual processing. Evolution may have favored neural systems capable of turning what a bird sees into action with minimal delay. But these are just hypotheses that have not been proven for now. The findings add to evidence that birds can achieve sophisticated feats without human-style brain anatomy. In 2020, Nieder’s team found that crows’ brains respond differently depending on whether the birds actually notice something they see, suggesting that crows may have a basic form of consciousness. Additionally, in 2024, researchers discovered that crows can count out loud, producing a specific number of calls, from one to four, when prompted. The latest work adds another twist: evolution not only found more than one way to build an intelligent brain. For at least one type of decision, you may have built a faster one. The study was published in the journal Science.
