Sexy Science

Despite the fact that jealousy can drive people to the most awful acts, it seems that it could be a tool for cementing relationships and, in moderation, may even be a good thing

THE woman known as "Madame Sex" caused sensation and scandal the world over in 2001 with her explicit sexual memoir, The Sexual Life of Catherine M, which chronicled her encounters with an "incalculable number" of sexual partners, often at orgies where she could get through literally scores of men. Given Catherine Millet's espousal of the merits of being a sexual libertine, her new book, Day of Suffering, makes a surprising revelation: that she suffered obsessive and desperate jealousy when her lover Jacques Henric, now her husband, decided to exercise some sexual freedom of his own.

Millet's crise de jalousie drove her to fits of rage and tears and she ended up on tranquilisers, so it seems that even the most sexually liberated among us can't escape the grip of the green-eyed monster, and most of us know how debilitating and stomach-churning that feeling can be. But evolutionary psychologists start from the premise that if you have a strong emotion appearing consistently in a given situation, then it must have some value in helping us to propel our genes into future generations. In other words, it must help us to survive and breed.

The most obvious function of romantic jealousy is that it helps us detect threats to a valuable relationship, so we can take action to defend it, and it turns out that men and women differ in the type of threats that elicit the strongest jealous reactions. Several studies have shown that a man is likely to react most intensely when his partner ends up in bed with another bloke, or looks like she fancies him. And while women are likely to be pretty unhappy about their mates' sexual infidelity, they tend to become even more distressed when he gets emotionally involved with another woman.

Considering the threats that sexual and emotional infidelity entail, this makes sense. If a man's partner has sex with someone else, then he could end up putting his time and money into another man's child while foregoing his own chance to reproduce. For women, it's easier to raise children with the help, commitment and resources of the father. If he plays away, it may be hurtful but doesn't necessarily mean he's going to stop that investment, but if he becomes emotionally attached to another woman, his partner could get left holding the baby.

Achim Schutzwohl of Bielefeld University in Germany carried out a study which showed that men are better at picking up cues to sexual infidelity and women are better at detecting a change of heart. But he also found that the target of our jealous feelings tends to be the same for both sexes: it's the woman. In the case of men, they heap their bad feelings on their partner when she has committed real or imagined infidelity, while women usually direct their jealousy at the rival, the "other woman".

Schutzwohl says that we're most likely to target the protagonist whose behaviour we stand the most chance of changing. Men more than women use physical violence to punish or prevent their partner's sexual infidelity, and sometimes this can spiral out of control with the deadly results that we hear about in the news with heartbreaking regularity, when some spurned man has murdered his wife or even his children.

Women, though, tend to direct verbal possession and sometimes aggression signals to other women they think might be making a play for their man. Women are also not averse to deliberately stirring up a bit of jealousy in their partners by flirting with other men, which can increase his commitment to her. And if he doesn't get jealous, she knows that the relationship probably isn't that important to him.

Sometimes a little bit of jealousy is needed to keep the passion going in a relationship. Novelist Howard Jacobson believes that male jealousy has an enormous role to play in love affairs, that there is something potentially thrilling about being jealous.

"I've always been interested," he said in interview, "in the way that jealousy can quicken love." And in Jacobson's latest book the main character secretly wants his wife to be unfaithful to him, for the paradoxical ecstasy of it.

Most of us wouldn't go that far, but maybe a little bit of jealousy, now and then, can be a good thing.