SCIENTISTS have identified 91 ways of keeping an adulterous affair secret – or how to fool your partner. The very signs that make a marriage look rock-solid can also be signs that it is on the rocks.

Psychologists found that one of the most effective ways for a man to keep his wife from suspecting he is having affair is simply to pretend greater interest in her and their future together. And a woman should beware the man who talks about spending "quality time" together, as this can be the hallmark of a cheat.

Meanwhile, a husband should be wary of a wife who suddenly demands more sex, seems unusually attentive and wears her wedding ring more often than before. In fact, husbands should pay the closest attention because, it turns out, women are far better at deception than men.

The researchers, whose results are reported in the Personality and Social Psychology Bulletin, looked at the tactics involved in what they call "human mate-poaching". It is the first study of how people set out to have an affair and what they do to cover it up.

The psychologists found that men and women had 51 different strategies for "poaching" a mate, and 91 ways of covering up the affair. The most effective way for a man to hide an extramarital affair is to talk with his current partner about their future together as a family. For a cheating wife, the most effective way is to keep up a veneer of normality, taking care not to change her daily routine, clothes or beauty regime in any way.

Professor Todd Shackelford of Florida University, and other psychologists looked at the ways in which people entice others into illicit relationships and then covered it up. They questioned cheating partners and reviewed earlier research into relationships and lying. Then they asked the cheats which techniques worked best and rated each for its effectiveness.

Professor Shackelford said: "The goal was to identify the acts men and women perform to disguise the fact that they are trying to attract a mate-poaching relationship. "The result was a list of 91 distinct acts of mate-poaching deception. The top three techniques for women involved maintaining everyday activities. Apparently, a woman's mate-poaching enticements can be camouflaged best by not letting her daily life become noticeably altered.

The report says a woman can also deceive her mate by giving him more affection and sex. "Both indicate that women can be especially effective at disguising a mate-poach from their partner by satisfying his need for frequent sex," it said.