Scientists have long been baffled by the smarts displayed by some birds with tiny brains.
But a new explanation may turn the term "bird brain" on its head: Birds have more densely packed neurons in their brains than other animals, contributing to cognitive ability on par with that of primates, researchers said on Monday.
A macaw's brain may be the size of a shelled walnut, far smaller than that of a macaque monkey -- which has a brain the size of a lemon -- but the parrot has many more neurons, or brain nerve cells, in its forebrain, a region crucial for intelligence, according to a study published in the Proceedings of the National Academy of Sciences.
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The researchers were the first to systematically measure neurons in the brains of 20 bird species ranging in size from the tiny finch to the six-foot (1.8-meter) emu.
"For a long time having a 'bird brain' was considered to be a bad thing," said senior author Suzana Herculano-Houzel, a neuroscientist at Vanderbilt University. "Now it turns out that it should be a compliment."
Parrots and crows have cognitive abilities similar to those of primates, the study found.
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