Crows make visual choices in half the time monkeys do

Carrion crows reach visual decisions in roughly 0.5 seconds, a speed that is double what primates require for the same task. This finding changes how scientists understand bird intelligence, showing that brains without a neocortex can process complex visual data with high efficiency. The result suggests that fast decision making does not strictly require the specific brain structure found in mammals.

The study, led by neurobiologist Andreas Nieder at the University of Tübingen, used a test called the random-dot-motion task. In this experiment, a cloud of flickering specks drifts weakly in one direction. The subject must determine if movement is present and identify its direction. In primates, neurons in the neocortex collect visual evidence over time. Their firing rates increase until they cross a threshold, triggering a final choice.

Birds lack a neocortex, which left a gap in scientific understanding regarding how they handle similar decisions. "This was the big question," Nieder said. "How [would] a differently organized avian brain encode decisions?" To answer this, Nieder and colleague Philipp Schmidbauer tested two hand-raised carrion crows. The birds sat in front of a touch-sensitive monitor displaying white dots on a black background.

The crows reported the direction of the moving dots by pecking one of the targets flanking the display. A correct answer earned a mealworm. The researchers kept the setup identical to the monkey version to ensure a fair comparison. "We intentionally wanted to have exactly the same random-dot motion task," Nieder said. "The only difference was that the crows had to peck to indicate their decision, whereas monkeys were indicating by making an eye movement."

The team varied the difficulty by changing the percentage of dots that moved coherently. At the easy end, 81 percent of the dots moved together, making the direction obvious. At the hardest end, only 3 percent moved coherently, making the signal barely distinguishable from noise. The team also included a condition where 0 percent of the dots moved, meaning there was no correct answer.

The crows solved the task using the same mathematical logic as primates. Their brains arrived at decisions through a comparable process despite being organized very differently. The primary difference was speed. The crows completed the visual processing tasks twice as fast as the monkeys. This demonstrates that a brain without a neocortex can achieve high-speed decision making using alternative neural pathways.