Crows solve visual puzzles with primate-like speed

Scientists have long relied on primate experiments to understand how biological brains process information and make choices. However, a new study suggests that avian brains, which lack the complex structure found in mammals, utilize a remarkably similar logical framework. The key difference is efficiency. Crows appear to reach final decisions twice as fast as monkeys when faced with ambiguous visual data.

The core of this inquiry centers on the random-dot-motion task. In this standard experiment, a subject watches a cloud of flickering specks that drift weakly in one direction. The animal must determine the overall flow of movement. In primates, researchers have observed that neurons in the neocortex gradually accumulate visual evidence. The activity of these cells rises until it hits a specific threshold, triggering a definitive choice.

This mechanism posed a puzzle for scientists studying birds, as they do not possess a neocortex. Andreas Nieder, a neurobiologist at the University of Tübingen, noted that this gap left the encoding process unclear. He described the situation as a major unanswered question regarding how a differently organized avian brain handles decision-making signals.

To address this, Nieder and colleague Philipp Schmidbauer conducted tests on two hand-raised carrion crows. The birds interacted with a touch-sensitive monitor displaying white dots against a black background. A subset of these dots moved coherently in one of four directions. The crows indicated their perception by pecking a target adjacent to the screen, earning a mealworm for each correct answer.

The team maintained strict consistency with existing primate protocols to ensure comparability. Nieder explained that they intentionally used the identical random-dot motion task for both groups. The only operational change was the method of response. Monkeys typically use eye movements to signal their decision, while the crows relied on beak pecks to communicate their choice.

The researchers adjusted the difficulty levels by varying the proportion of dots moving together. The easiest condition involved 81 percent of dots moving coherently, making the pattern obvious. The hardest condition used only 3 percent, creating a signal that was barely distinguishable from random noise. A zero percent condition was also included to test scenarios with no correct answer.

The results showed that the crows solved the task using the same mathematical logic as primates, despite their distinct brain architecture. More significantly, the birds processed the information and made decisions at a rate twice as fast as the monkeys. This finding suggests that a brain without a neocortex is fully capable of executing comparable decision-making processes with greater speed.