Tailing Lateralization

A dog's tail reveals unambiguous messages about its mood. Now, a study on tail wagging may lend credence to the contested theory that nonhuman vertebrates have asymmetric brain function. Angelo Quaranta and colleagues from the University of Bari and the University of Trieste in Italy trained video cameras on the posteriors of 30 dogs while exposing them to four separate visual stimuli: the dog's owner, an unfamiliar person, a dominant unfamiliar dog, and a cat.

Familiar and nonthreatening sights induced right-biased wagging, indicating left side "approach" brain activation. The dominant unknown dog procured left-leaning wags, indicating right brain "withdrawal." Peter MacNeilage, a member of the Faculty of 1000 and a University of Texas professor in psychology, calls the work "a confirmation of what others have argued" - that nonhuman vertebrates have behaviors linked to specific brain hemispheres.

Prior to this research, he says, "In a single subject population, not one study has shown both avoidance and approach. ... Usually when people study the two hemispheres, they use different experimental paradigms. In this case [Quaranta] uses the same experimental paradigm, making it more consistent. This paper supports the theory that when one half of the brain is sensing some danger, it's more connected to the opposite side of body." A mystery remains, however: "Why do animals have this brain lateralization in the first place?"

These papers were selected from multiple disciplines from the Faculty of 1000, a web-based literature awareness tool (www.f1000biology.com).