Carrion crows make decisions twice as fast as primates

Carrion crows can interpret visual information and make decisions in an average of 235 milliseconds, about twice as fast as humans and other primates in comparable conditions, ERR reports.

Neurobiologists at the University of Tübingen, led by Andreas Nieder, tested two crows using a touchscreen task to study how quickly their brains process what they see. The birds watched white dots move against a black background. Some dots moved consistently to the left or right, while the rest moved randomly. The crows had to identify the overall direction and tap the correct symbol with their beaks. A correct answer earned them a mealworm.

The researchers varied the difficulty by changing the proportion of dots moving in the same direction. When only 3 percent moved together, the visual cue was very subtle. Even then, the crows chose correctly 56 to 57 percent of the time, well above chance. When the direction was clear, their accuracy approached 100 percent. Accuracy remained stable across the rounds, even when the birds responded quickly.

The researchers also recorded electrical activity from 248 individual nerve cells in the crows’ brains. The cells gathered visual information until their electrical activity passed a threshold and the brain made a decision. Based on this activity, the researchers could predict a crow’s choice 70 milliseconds after the dots appeared, 170 milliseconds before the bird touched the screen with its beak.

Birds do not have the layered cerebral cortex that helps humans and monkeys solve complex tasks. Instead, the nidopallium caudolaterale performs comparable functions to the primate frontal lobe. The researchers said the decision-making process they observed in crows closely resembled processes previously recorded in humans and monkeys.

Birds and mammals diverged more than 310 million years ago. The study’s findings suggest that evolution arrived independently at the same computational solution in both groups.