Only one in three of us turn left to snog.
For the past two and a half years, neuroscientist Onur Güntürkün has hung around airports, railway stations, parks and beaches, watching people kiss. "After two years, I could feel when people were approaching to kiss," he says.
His motives were scientific. Güntürkün, who works at Ruhr University in Bochum, Germany, was noting which way kissers turn their heads. They turn to the right twice as often as to the left, he found1.
About twice as many people also prefer their right foot, eye and ear to their left. But the head-turning habit precedes all of these: it develops during the final weeks in the womb. Until now, no one knew whether adults retained it.
"I think head-turning comes first, and the body has a tendency to attend to the right side," says Güntürkün. The initial preference may be small, but experience reinforces it until kicking a ball with the left foot - or approaching a kiss from the left - feels weird.
It's a reasonable idea, comments child-development researcher David Lewkowicz, of the New York State Institute for Basic Research in Developmental Disabilities. "Babies attend and act more to the right," he says. "All of these things cascade one after the other."
Kiss and tell
Güntürkün's study began during a five-hour stopover in Chicago. He realized that airports, where loved ones from many races and cultures mix, are good places to collect data on whether adults have a head-turning preference. But getting a good kiss turned out to be a lot harder than he thought.
Pecks on the cheek were out, as "they're deeply influenced by culture", says Güntürkün. Also excluded was any kisser who was carrying something - a shoulder bag, for example - that might skew their movements. Five hours yielded only a couple of data points.
“Pecks on the cheek are deeply influenced by culture Onur Güntürkün , Ruhr University, Germany”
Over the next two and a half years, Güntürkün recorded 124 scientifically valid kisses in public places across the United States, Germany and Turkey.
When not watching snoggers, Güntürkün also studies chicks, most of which turn their heads to the right inside the egg. Such off-centre trends are widespread in vertebrates.
For hands, the rightist tendency is far stronger - there are eight for every lefty. This may be because handedness is controlled differently to other preferences, or there may be cultural influences that drive more people to use their right hands.
Güntürkün, O. Adult persistence of head-turning asymmetry. Nature, 421, 711, (2003).
Ruhr University, Germany