Secret of true love revealed

Love, according to romantics, can have a dramatic effect on the senses - striking lovers blind, deaf or rendering them tongue-tied but the simple answer to the question of whether any relationship is "the one" seems to be that your ideal man or woman gets up your nose.

In the new study researchers looked for the first time at the effect of being born without a sense on smell on men and women's relationships.

The research involved analysing data on men and women aged 18 to 46 with no sense of smell and comparing it with information gleaned from a healthy control group.

The results showed that men and women who were unable to smell had higher levels of social insecurity, although this manifested itself in different ways.

In men, but not in women, it led to fewer relationships. The men with a faulty sense of smell averaged two partners compared with 10 for healthy men.

One theory is that the lack of a sense of smell may make men less adventurous. They may have more problems assessing and communicating with other people. They may also be concerned about how they are perceived by others, and worry about their own body odour.

The two groups of women had the same average number of sexual partners - four. But the women who couldn't smell well lacked confidence in their partners - they were around 20 percent less secure in their relationship than the women in the control group.

Lacking a sense of smell had no impact on their relationships with close friends, suggesting that smell plays a role for women specifically when it comes to their partners.

"The sense of smell provides social information about others," the researchers from the University of Dresden said.

"Its absence is related with reduced social security in men and women, and affects partnership. Men exhibit much less explorative sexual behaviour and women are affected in a way that they feel less secure about their partner. Our results show the importance of the sense of smell for social behaviour," they said.

The role of smell as a trigger for arousal in men features widely in fiction, from Patrick Suskind's ‘Perfume: The Story of a Murderer' to Al Pacino's lead role in ‘Scent of a Woman', where blind Colonel Frank Slade can name or describe the appearance of women by their perfume alone.

Phillip Hodson, a psychotherapist and author of "How ‘Perfect' Is Your Partner?" described the new study as "a very astute piece of work."

"Instead of testing pheromones - which control moths but may not control humans - they've studied the smell-disabled to see how they differ from the rest. And both sexes with faulty noses appear to be less than sexually confident. We know the nose is a sexually interactive organ: it tends to run when we get aroused and often people sneeze when extremely excited," he said.

"The French take the subject so seriously they even have a word for the scent of a woman when perfume is mingled with body oil: her cassolette," he added.

The study has been published in the journal Biological Psychology.