A new study provides further evidence of the high level of intelligence in crows. When faced with a visual choice, these birds arrive at the correct decision twice as fast as humans or monkeys. Moreover, the decision-making process within their brains unfolds in much the same way as it does in primates.
In the past, the avian brain was often underestimated. However, it has become increasingly clear that, despite structural differences, the brains of birds are capable of supporting high-level cognitive functions similar to those found in mammals.
Crows are widely considered to be among the most intelligent birds. It has been shown that they can use tools, remember past grievances, and even hold “funerals” for their peers. The findings of a new study, published in the journal Science, add another entry to the list of the intellectual feats of crows: the ability to make accurate decisions based on visual information with lightning speed.
Neuroscientists Andreas Nieder and Philipp Schmiedbauer from the University of Tübingen (Germany) trained two carrion crows (Corvus corone) to perform a visual task on a touchscreen. The birds observed white dots moving against a black background; some of the dots moved in a specific direction (left or right), while others moved randomly. The crows’ task was to determine the dominant direction of movement and peck the corresponding area on the screen, for which they were rewarded with a mealworm.
By adjusting the ratio of dots moving in a single direction, the researchers were able to vary the difficulty of the task. When the majority of the dots moved in one direction, it was relatively easy for the birds to make the correct choice. If only a small fraction of the dots moved in a coordinated fashion, the birds had less visual data to rely on when making a decision.
Experiments showed that crows are capable of making deliberate decisions with striking speed: on average, they determined the direction of the dots’ movement on a screen in approximately 235 milliseconds—less than a quarter of a second—without any loss of accuracy. Similar experiments involving monkeys or humans have shown that it takes them about twice as long to reach a decision.
When many dots were in motion and the direction was clearly defined, the accuracy of the crows’ responses approached 100%. Even when only 3% of the dots moved in a coordinated way, both birds performed significantly better than they would have by mere chance, providing the correct answer 50% of the time. This high level of accuracy indicates that the crows did not sacrifice the quality of their judgments for the sake of speed, the researchers noted.
To understand how the birds manage to make decisions so quickly, Nieder and Schmidbauer recorded the activity of 248 neurons in the nidopallium caudolaterale (NCL)—a region of the avian brain that is functionally comparable to the prefrontal cortex in humans and primates. Although birds lack the layered cerebral cortex characteristic of mammals, the NCL performs equally complex functions.
In primates, neurons accumulate sensory information, and their activity increases until a critical threshold is reached, at which point the brain makes a decision. The researchers concluded that crows appear to employ a similar mechanism.
Based on this neural activity, the scientists were able to predict a crow’s choice as early as 70 milliseconds after the dots appeared. This occurred approximately 170 milliseconds before the birds performed a behavioral response—in this case, pecking at a screen.
“Flight places enormous demands on visual information processing and sensorimotor coordination. Birds must navigate three-dimensional space, avoid obstacles, and react quickly to moving objects. Foraging for food and hunting prey also require making rapid, accurate decisions. It is likely that such conditions fostered the development of an ability to process information quickly,” Nieder explained.
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