Crows have their own version of the human cerebral cortex.
Corvids — the “crow family” of birds that includes ravens, jays, magpies, and nutcrackers — are intelligent. They utilize tools, identify faces, leave gifts for individuals they like, and one Facebook video shows a crow forcing a recalcitrant small hedgehog out of traffic. Corvids will also throw boulders into the water to attract floating food.
What the authors of a new study published last week in the journal Science discovered may surprise you: Crows are capable of thinking about their own ideas while they solve issues. This is a level of self-awareness that was formerly thought to represent the kind of higher intelligence that only humans and probably a few other mammals possessed. A crow knows what a crow knows, and if the phrase sentience comes to mind, you may be correct.
Higher intellectual functioning has long been thought to be solely the result of a layered cerebral cortex. However, bird brains are unique. The researchers discovered that crows’ unlayered yet neuron-dense pallium may have a comparable purpose for the avians. Another study published last week in Science suggests that the neuroanatomy of pigeons and barn owls may potentially enable higher intellect.
“It’s been a wonderful week for bird brains!” says University of Washington crow expert John Marzluff. (He was not a participant in either study.)
Corvids are thought to be as intelligent as monkeys and big apes. However, because bird neurons are so little, their palliums actually contain more of them than an equivalent-sized monkey cortex. This could be an indication of their broad mental ability.
In any case, there appears to be a general correlation between the amount of neurons in an animal’s pallium and intellect, according to Suzana Herculano-commentary Houzel’s for Science on both new findings. Despite our much lower body size, humans, she claims, rank “satisfyingly” atop this comparative chart, with even more neurons than elephants. Crow brains are thought to have 1.5 billion neurons.
The increased intelligence crows shown in the latest study is similar to how we solve problems. We collect relevant knowledge and then experiment with different combinations of what we know to come up with an action or solution.
The researchers trained two carrion crows (Corvus corone), Ozzie and Glenn, under the supervision of neurobiologist Andreas Nieder of the University of Tübingen in Germany.
The crows were taught to look for a flash of light — which did not always materialize — and then peck at a red or blue target to indicate whether or not a flash of light was seen. Ozzie and Glenn were also taught to recognize a changing “rule key” that indicated whether red or blue indicated the presence of a flash, with the other hue indicating no flash.
Following each round of testing, the crows were shown a rule key indicating the current meaning of the red and blue targets, following which they pecked their response.
This procedure kept the crows from just rehearsing their response on auto-pilot. In each test, participants had to start from the beginning, seeing a flash or no flash and then determining which target to peck.
Throughout this process, the researchers examined their neural activity. When Ozzie or Glenn witnessed a flash, sensory neurons responded briefly before stopping as the bird determined which object to peck. When there was no flash, no sensory neurons fired before the crow paused to determine the correct target.
According to Nieder’s interpretation of this sequence, Ozzie or Glenn had to see or not see a flash, deliberately note whether or not there had been a flash — demonstrating self-awareness of what had just occurred — and then, in a few moments, connect that recollection to their knowledge of the current rule key before pecking the correct target.
During the few moments following the cessation of sensory cell activity, Nieder reported activity among a wide population of neurons as the crows put the puzzle pieces together in preparation for reporting what they’d seen. The pallium was one of the busiest locations in the crows’ brains throughout this stage of the process.
Overall, the study suggests that the layered cerebral cortex may no longer be required for higher intelligence. As we learn more about crow intelligence, we can declare with some assurance that it is best to avoid provoking one.
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