A study published today in the journal Science reveals that carrion crows (Corvus corone) can complete visual perceptual decision-making tasks in approximately 235 milliseconds — roughly twice as fast as monkeys and humans. The finding, conducted by Philipp Schmidbauer and Andreas Nieder of the University of Tübingen in Germany, not only challenges the notion that cognitive speed is tied to brain architecture, but also illuminates a fascinating aspect of convergent evolution: structurally different brains can arrive at the same outcomes, and in some cases, surpass mammals.
The experiment was simple in its logic but rigorous in its execution. Two crows, nicknamed Iggy and Lemmy in the laboratory, were trained to identify the predominant direction of movement of white dots displayed on a touchscreen. Some of the dots moved left or right in a coordinated manner; the rest moved randomly. The birds needed to peck the correct point on the screen to indicate their response — left or right — and were rewarded with food when they were correct. The test measured not only speed but the ability to make a deliberate decision based on ambiguous visual stimuli, integrating enough information before acting.
The results were striking. On average, the crows responded in 235 milliseconds, with 74% accuracy — a level comparable to primates in identical tasks, but half the time. When motion patterns were particularly difficult to discern, with only 3% of dots moving coherently, the birds still exceeded chance, demonstrating that they were not sacrificing accuracy for speed. "We've never forced the crows to be as quick as possible," Nieder explained. "We just gave them a self-paced decision." The fact that they performed so well in their own pace suggests that the extreme speed observed is not an artifact of stress or experimental pressure, but rather a natural cognitive capacity of the species.
What makes the finding truly extraordinary is the neurophysiology behind it. While mammals rely on the cerebral cortex — a layered structure that houses the prefrontal cortex, responsible for reasoning and decision-making — birds do not possess a neocortex. Instead, crows and other corvid species use a structure called the nidopallium caudolaterale (NCL), a region of the endbrain that is functionally analogous to the primate prefrontal cortex but is built in a radically different way. In mammals, information is processed by circuits organized in vertical layers. In crows, the same processing occurs through densely packed fusiform cell nuclei, without any of the layer divisions that define mammalian brains.
Neural recordings made during the tasks showed that NCL neurons exhibited ramping signals — patterns of increasing activity that precede and predict the bird's choice — in essentially the same way observed in primate prefrontal cortex. In other words, the mathematical logic behind perceptual decision-making is the same; only the hardware architecture is entirely distinct. It is one of the best documented examples of convergent evolution in action: two lineages separated by more than 300 million years of evolutionary divergence arrived at an equivalent computational solution.
So why are crows so fast? Nieder proposes several hypotheses, all plausible but still without definitive answers. One has to do with brain size. Birds' brains are much smaller than mammals', which means axons are shorter. Shorter wires = faster signal travel. It's the same reason that smaller chips operate at higher frequencies: less distance for electricity to travel. Another hypothesis concerns neuronal density. Compared to primates, corvids have two to three times more neurons in the same volume of brain tissue. More processors per cubic centimeter potentially means more decision cycles per unit of time.
There is also the question of body temperature. Birds maintain higher body temperatures than mammals, which could accelerate ion channel opening and neurotransmitter flow across synaptic clefts. "These are some hypotheses, but this is an entirely wide-open research question," Nieder said. The biophysics itself favors avian speed; what remains are empirical data isolating each variable.
The study does not investigate more complex types of decisions — economic choices, risk assessments, or long-term evaluations. The task was strictly perceptual and visual. Nevertheless, the finding has broad implications. Since the 2010s, comparative neuroscience has been dismantling the notion that birds' brains are "fish brains" with feathers. Crows use tools. They recognize geometric patterns. They count. They plan future actions. Now, we know they can also evaluate visual stimuli and decide with a speed that puts primates in second place.
What remains open — and what will likely define the next wave of research — is whether this extraordinary speed is a general characteristic of birds or something specific to corvids. "Among birds, the corvids are renowned to be extremely intelligent," Nieder said. Marc Schmidt, a professor at the University of Pennsylvania who was not involved in the study, captured the sensation the work provokes: "Holy cow!" he said reading the numbers. "This study shows the power of the comparative approach, and how much we can learn and how much we can be surprised."
Bird brains' smaller size, shorter axons, and high neuronal density make them a hardware naturally optimized for rapid processing. The question remains whether this advantage is exclusive to corvids or a more general trait of birds. A crow observing city traffic is likely processing visual information at a speed no human could match.
Sources: Science, The Transmitter, University of Tübingen
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