Crows Decide in 235 Milliseconds, Twice as Fast

A carrion crow can call a visual decision in about a fifth of a second. In a University of Tübingen study published in Science on October 22, two crows judged the main direction of a cloud of moving dots in 235 milliseconds on average. That's roughly twice as fast as monkeys and humans have managed in matched versions of the same test, and the birds didn't trade away accuracy to get the speed.

The test is a classic. Dots drift across a touchscreen, some moving together and some scattering at random, and the subject reports whether the group leans left or right. Primates have taken versions of it for decades, and their times cluster far above the crows': about 410, 490 and 600 milliseconds across three earlier monkey studies. The Tübingen birds, two hand-raised carrion crows, pecked their answers in less than half the slowest of those times.

The brain recordings explain where the speed comes from. Philipp Schmidbauer and Andreas Nieder, at the university's Institute of Neurobiology, recorded 248 neurons in the nidopallium caudolaterale, an associative region of the bird brain that plays a role comparable to the prefrontal cortex in mammals. Direction-selective neurons there encoded the crow's upcoming choice about 70 milliseconds after the dots appeared, roughly 170 milliseconds before the bird moved its head to answer.

The structure makes the result hard to file as a trick. A crow brain has no neocortex, the layered sheet that mammals use for this kind of computation. The Tübingen team found the same basic decision signal running on different hardware: evidence gathering in a pallial region, a choice forming early, and a fast motor answer once the signal settles. Two very different brain designs converged on the same logic, and the bird's version runs quicker.

The limits are plain, and the researchers state them. The study rests on two birds, which is the standard sample for monkey experiments that combine behavior with single-neuron recordings, but it's still two birds. Nobody tested monkeys or people side by side with the crows in the same lab, so the two-to-one gap is a comparison against published times, not a head-to-head race. What the result establishes is narrower and still striking: an avian brain can run a deliberate perceptual decision at a speed the primate literature hasn't matched.