Science on the Edge

We used to think that "handedness" was a characteristic unique only to humans, but recent research is suggesting that it is present, and possibly even common, in other vertebrate groups. A recent publication in Biology Letters by a group of researchers from Macquarie University in Australia tested for the presence of handedness in 322 birds from 16 parrot species found in Australia. They found that in all but one species (the cockatiel) the eye the birds used to look at their food corresponded to the foot they used to pick it up, and that this relationship was carried on through their lives. In four of the species tested, near exclusivity in handedness (or footedness, I guess) was found, with the Sulfur-crested cockatoo still having no right-handed individuals to speak of. This suggests that the handedness characteristic has become fixed in these populations.

Extreme handedness situations like those found in these parrot populations are some of the only known cases outside of humans (we have about a 90:10 ratio). Some of the previous research done in this research area has shown that handedness in humans reflects the use of one brain hemisphere over the other, a behaviour that scientists call "laterality". The presence in animal species for one limb over the other suggests that an animal's brain function may also be lateralised, with one side of the brain dominating control of certain functional tasks (like picking up food). The researchers believe that the hemisphere of the brain associated with food selection may also be the hemisphere associated with the determination of handedness. It is interesting to note that juvenile parrots will experiment with each foot before settling on one, much like what human children do.