Of a right mind to fight

Natural History, Oct, 2002 by Stephan Reebs

A male tree lizard is sunning itself on a rock by the side of U.S. Highway 80 in New Mexico. Suddenly a competitor, another male, appears a few feet away. Never mind that this intruder is in fact introduced by an experimenter working behind the scene; tempers may still flare and a lateral display (the lizard showing one side to its opponent) may ensue, perhaps even followed by a charge. The stage is set for a study by Diana K, Hews and R. Andrew Worthington, of Indiana State University. Their objective: to determine if aggression is controlled by one side of the brain more than by the other. Their results: lizards that spotted the intruder with their left eye were more likely to present with their left side, and lizards that displayed with their left side were twice as likely to charge. Since information from the left eye is processed first in the brain's right hemisphere, these findings provide additional support for the idea that this hemisphere plays the greater role in aggression. (Previous studies on Siamese fighting fish and toads, as well as on humans and other primates, have yielded similar results.) Drawing conclusions about human behavior from such studies is always risky, but highway drivers should perhaps try to ignore cars aggressively passing on their left (don't succumb to road rage!). Far better instead to look for lizards sunning on the right side of the road. ("Fighting from the right side of the brain: left visual field preference during aggression in free-ranging male tree lizards [Urosaurus ornatus]," Brain, Behavior and Evolution 58, 2001)

Stephan Reebs is a professor of biology at the Universite de Moncton in New Brunswick, Canada, and the author of Fish Behavior in the Aquarium and in the Wild (Cornell University Press).