Lateralized brains are not unique to humans. Parrots prefer picking up things with their left foot. Toads tend to attack other toads from the right but go after prey from the left. Zebra fish are likely to look at new things with their right eye and familiar things with their left. Even invertebrates are biased. Pinar Letzkus, a vision researcher at Australian National University, rewarded bees with sugar whenever they extended their tongue at the sight of a yellow rectangle on a computer screen. He then fashioned tiny eye patches and put them on a new set of subjects. Bees with their left eye covered learned almost as quickly as did bees without a patch. But bees with their right eye covered did far worse.
The broken symmetry of the nervous system may thus be as old as the symmetry itself. If so, it is an ancient puzzle. Being biased to one side would seem like a serious handicap: A toad that hopped to the left whenever it was startled by a predator, for instance, would be easy prey for an attacker that could anticipate which way it would go; the same holds for any other kind of ingrained behavioral imbalance. A number of scientists have run experiments to find the benefits that might offset such costs.
One hypothesis is that a lateralized brain is more powerful than one that works like a mirror image. Instead of two matching parts of the brain performing an identical task, one can take charge, leaving the other free to do something else.
No comments:
Post a Comment