Crows can make visual decisions in just 235 milliseconds, nearly twice as fast as humans, according to a study published in the journal Science. This rapid processing is enabled by a brain region that mirrors the function of the human prefrontal cortex, despite a vastly different brain structure.
Lightning-Fast Choices
Researchers at the University of Tübingen in Germany trained two carrion crows, Iggy and Lemmy, to watch moving dots on a touchscreen and determine their direction. The birds indicated their choice by pecking a corresponding target to receive a mealworm reward. The crows made their decisions in an average of 235 milliseconds, a speed that roughly doubles the time taken by humans and monkeys in similar experiments.
“Even when the patterns of motion were hard to recognize, the crows’ decisions were still better than random choices,” said Philipp Schmidbauer. He added that with clear signals, they achieved an accuracy of nearly 100 percent
.
In prior experiments, humans and monkeys had also completed this random-dot motion discrimination task. A comparison of this data showed that monkeys took approximately 410 to 600 milliseconds to make similar visual decisions, while humans took 450 to 820 milliseconds, confirming the crows’ superior speed.
The test was self-paced, with the crows given a wide window of time to choose their response. The birds had undergone extensive training, completing more than 100 sessions each before the data for the study was collected to ensure they fully understood the task.
A Different Brain, a Familiar Calculation
The study also examined the crows' brain activity. The researchers implanted electrodes to monitor the nidopallium caudolaterale (NCL), a brain region analogous to the prefrontal cortex in humans, which is crucial for decision-making. They found that direction-selective neurons in the crows’ brains began encoding the upcoming choice as early as 70 milliseconds after the dots appeared on the screen.
Neural activity then increased gradually as the birds processed the visual information, eventually reaching a particular threshold associated with making a decision. The researchers noted that these neural signals mirrored both the distinctness of the movement patterns and the final direction chosen by the birds.
These findings show that neuronal dynamics in the avian brain are consistent with established models of decision-making in humans and nonhuman primates,
said Andreas Nieder, a co-author of the study. This suggests that different brain structures can achieve similar high-level cognitive functions.
Unlike primates, birds do not possess a layered cerebral cortex. However, their body-to-brain mass ratio
is remarkably high, packing an enormous number of neurons into a small volume. Nieder noted that with this independently evolved endbrain design, the corvid brain affords twice as many neurons as a primate brain of equal mass, adding up to enormous processing powers in a small and densely packed ‘birdbrain’
.
Evolutionary Pressures for Speed
The researchers believe the crows’ remarkable speed is an evolutionary adaptation to their lifestyle. In terms of being able to make rapid decisions based on visual inputs, birds are under some of the strongest selection pressure given their dependence on rapid movement during flight
, the study noted.
Birds rely on their vision to carry out precise, rapid maneuvers during flight and to guide their beaks toward objects when foraging,
Nieder explained. This constant demand for rapid visuomotor control may have shaped the extraordinary efficiency of the avian decision-making circuitry. The study highlighted that these findings highlight the extraordinary efficiency of avian decision-making circuitry, possibly shaped by evolutionary pressures for rapid visuomotor control
.
Mike Colombo, a neuroscientist at the University of Otago in New Zealand who was not involved in the study, told NPR that it’s not about the architecture
, agreeing that different brain structures can achieve similar computations. Aaron Blaisdell, a neuroscientist at the University of California, Los Angeles who also did not participate in the study, questioned the prevalence of this swift characteristic among birds, wondering whether it was something that’s avian versus mammal, or is it something about crows specifically?
The findings add to a growing body of evidence that birds can achieve sophisticated cognitive feats without human-style brain anatomy. The study, titled Ultrarapid decision-making in an avian brain,
was published in Science.
