Güntürkün explained in his paper that to be included in this study, the act had to meet a few kissing criteria: lip contact, face-to-face positioning, no hand-held objects, and an obvious head-turning direction during the kiss.
It turns out that roughly twice as many people turn their heads to the right when they go in for a kiss than to the left. Of the 124 pairs observed, 80 turned their heads to the right and 44 to the left.
This right-kissing, two-to-one bias is the same ratio as the bias toward the right foot, ear, and eye, according to Güntürkün. Preference for the right hand is eight to one, but scientists believe it is skewed because of cultural pressures.
"These data suggest that a head-motor bias still persists in adulthood and could therefore modulate the establishment of various forms of sidedness over the entire lifetime," said Güntürkün.
Chris McManus, a psychology professor at University College London and author of the book Right Hand, Left Hand published by Harvard University Press in 2002, questions the methodology of Güntürkün 's find.
McManus said that it may be possible that head-turning preferences of babies are the root of preferences for one side or the other, "but the only way to test the hypothesis is to follow infants whose head-turning direction is known."
Güntürkün did not know the couples he observed, so did not know if they turned their heads to the right or left as infants. However, Güntürkün believes his research may eventually show that head-turning preference is one of the very few sided behaviors controlled by genetics, and that all others are secondary.
Daniel Geschwind, a research scientist with the Center for Neurobehavioral Genetics at the University of California at Los Angeles, said it is unclear whether this head-turning behavior is related to other types of asymmetries such as being right-eared and right-eyed.
"The reason other asymmetries are interesting is they have a lot to do with early patterning, such as language," he said. Ear-sidedness, for example, is related to language. "It is unclear if this is related to any of that."
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