Lessons from a Bird Brain

Right-footed parrots offer pointers on how the mind organizes language.

"Nous parlons avec l'hemisphere gauche!" ("We speak with the left hemisphere!") declared the French neurologist, Paul Pierre Broca in 1864. The halves of the brain watch over distinctly different tasks and, as Broca noted, speech is the provenance of the brain's left side. A century and a half later, that principle of brain function remains largely true--that is, unless you happen to be left handed. Unlike righties, some left handers use parts of their right brain for processing language.

Are these fundamental asymmetries in brain function a peculiarity of humans or do their roots lie deep in the evolutionary history of the mind? Intrigued by that question, Peter Snyder, a neuroscientist at Allegheny General Hospital in Pittsburgh, went looking for a suitable animal model. Just down the street at the National Aviary, Snyder found some perfect candidates: parrots. Right footed African Grey parrots, Snyder says, know more words than their lefty brethren. Here then might lie a clue to the brain's odd division of labor.

For 300 years people have noted the parrot's dexterity and tendency to favor one foot over the other when handling food, Snyder reports. But all of the scientific attempts to quantify this behavior were deeply flawed. Snyder therefore began by developing the largest and most accurate study to date of parrot footedness, encompassing the pedestrian habits of more than 500 birds. He created questionnaires describing a set of experiments and strict guidelines for carrying them out; he then published these both in bird magazines and on the Internet. From the responses, Snyder concluded that parrots in general show a tendency toward left footedness. Among one species, the Australasian Cacatuinae (cockatoo), 82% of the birds are left-footed--close to the percentage of humans who are right handed. That degree of lateral preference is unknown in any other vertebrate animal, including our primate cousins.

Hoping to find a link between brain function and footedness, Snyder focused on the best avian articulators around, the African Greys. Parrot owners reported on the size of their Psittacinan sidekicks' vocabulary, providing lists of up to 300 words. Amazingly, the right-footed birds had memorized a significantly larger number of words than their left-footed counterparts. Even after adjusting for age and for how pushy the owners were about teaching them to talk, right-footers won wings down.

As in humans, the left side of a bird's brain controls the right side of its body, and vice-versa. Likewise, studies in chickens show that avian memory for categories (like words) resides in the left hemisphere. Snyder therefore suggests that "right footedness might be a behavioral measure of preferential activation of the contralateral (left) hemisphere." Until now there was little evidence of a connection between motor dominance and higher cognitive functions in any animal other than humans.

The evident link between foot preference and language skills in parrots is especially striking because avians split off from our branch of the evolutionary tree some 150 million years ago. Perhaps birds and people have followed a strangely parallel evolutionary path, Snyder notes, or else they share brain asymmetries inherited from an even older ancestor. Either way, he believes that the new findings will improve scientists' understanding of why our brains are organized they way they are, and of how brains adopt a preferred handedness during fetal development. Such information could lead to new insights into the nature of brain disorders, such as those associated with strokes and epilepsy.

Snyder plans to extend his work by directly measuring parrots' mnemonic abilities--testing their ability to distinguish objects by color and shape, for instance, or to count a number of objects. Such experiments have been successfully done on primates and on one famous research parrot, Alex, but testing a large sample of parrots will be difficult. Until now, "I don't think anybody's been crazy enough to do this test with 80 to 100 birds," he says. "I think I may be that crazy person."

--Samuel K. Moore Posted 2/23/1998

(c) Copyright 1998 The Walt Disney Company.