How small can a brain get, and still work?

Anthropologists like to distinguish humans from other animals, by pointing to our large brain capacity, and our ability to learn and imitate language. But new research suggest the lowly hummingbird, with a brain smaller than the size of a pea, may share some of our most complex abilities. I'm Jim Metzner, and this is the Pulse of the Planet.

Erich Jarvis is an Assistant Professor of Neurobiology at Duke University Medical Center. He's comparing brain activity of hummingbirds with that of other animal species that can learn and reproduce sounds.

"Hummingbirds have taught me that brain size does not matter. They have one of the smallest brains in the world, and yet they do behaviors that are very complex, similar to humans. Dogs for instance, or cats, have much larger brains than hummingbirds. But they don't have this ability to imitate sounds. So size does not matter, it's the actual structures in the brain that matter."