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Kisses unleash chemicals that ease stress

In an experiment in the US, it was found that kissing unleashes chemicals that ease stress hormones in both the sexes and encourage bonding in men, though not so much in women.

world Updated: Feb 15, 2009 15:01 IST
Randolph E. Schmid
Randolph E. Schmid

“Chemistry, look what you’ve done to me,” Donna Summer crooned in Science of Love, and so, it seems, she was right. Just in time for Valentine’s Day, a panel of scientists examined the mystery of what happens when hearts throb and lips lock.

Kissing unleashes chemicals that ease stress hormones in both the sexes and encourage bonding in men, though not so much in women.

Chemicals in the saliva may be a way to assess a mate, Wendy Hill, dean of the faculty and a professor of neuroscience at Lafayette College, said in a meeting of the American Association for the Advancement of Science on Friday.

In an experiment, pairs of heterosexual college students who kissed for 15 minutes while listening to music experienced significant changes in their levels of the chemicals oxytocin, which affects pair bonding, and cortisol, which is associated with stress. Their blood and saliva levels of the chemicals were compared before and after the kiss.

Both men and women had a decline in cortisol, an indication of their stress levels having reduced. For men, oxytocin levels increased, indicating more interest in bonding.

In a test group that merely held hands, chemical changes were similar, but much less pronounced, said Hill. The experiment was conducted in a student health centre, though she plans a repeat “in a more romantic setting.” Hill spoke at the session on the Science of Kissing, along with Helen Fisher of Rutgers University and Donald Lateiner of Ohio Wesleyan University.

Fisher noted that more than 90 per cent of human societies practice kissing, which she believes has three components — the sex drive, romantic love and attachment.

The sex drive pushes individuals to assess a variety of partners and then romantic love causes them to focus on an individual. Attachment then allows them to tolerate this person long enough to raise a child.

Men tend to think of kissing as a prelude to copulation, Fisher said.

She noted that men prefer “sloppy” kisses, in which chemicals including testosterone can be passed on to the women in saliva, which increases the sex drive of men and women. Overall, the science of kissing — philematology — is under-researched, Hill concluded. “When you kiss an enormous part of your brain becomes active,” she added.

First Published: Feb 15, 2009 13:26 IST