Are you really into me?

Published in Computers in Human Behavior, the study by researchers from Israeli-based Interdisciplinary Center Herzliya and the University of Rochester finds that uncertainty about potential partners' romantic interest decreased their sexual appeal.

"People may protect themselves from the possibility of a painful rejection by distancing themselves from potentially rejecting partners," explains study co-author Harry Reis, a professor of psychology and Dean's Professor in Arts, Sciences & Engineering at Rochester.

While some scientists have argued that uncertainty spices up sexual desire, Reis says his team's results suggest the opposite holds true. "People experience higher levels of sexual desire when they feel confident about a partner's interest and acceptance," says Reis.

Lead author Gurit Birnbaum, a social psychologist and associate professor of psychology at the IDC Herzliya, says the findings suggest that sexual desire may "serve as a gut-feeling indicator of mate suitability that motivates people to pursue romantic relationships with a reliable and valuable partner." Conversely, "inhibiting desire may serve as a mechanism aimed at protecting the self from investing in a relationship in which the future is uncertain."

Are you really into me?

Over the course of six interrelated studies -- some of them experimental and some daily diary entries -- the researchers examined whether and under what circumstances uncertainty about a partner's romantic intentions would affect their partner's sexual desirability.

In the first study, 51 women and 50 men from a university in central Israel who identified as single and heterosexual, ranging in age from 19 to 31 years, were led to believe they would be participating in an online chat with another participant who was located in a different room.

Next, participants had their picture taken and were told it would be shown to the other person, who was in fact an insider, working with the scientists. Then the researchers showed the study participants a photograph of their purported chat partner. In reality, all participants were shown the same picture of an opposite-sex individual. At the end of the chat via Instant Messenger, the scientists told the participants that they were allowed to send one last message to their "partner." Some participants were told that a message from their chat partner was waiting for them; others were told there was no message, thereby creating either certainty or uncertainty, respectively, about the potential partner's intentions. Afterwards, the researchers asked the participants to rate the insiders' sexual desirability and their interest in future interactions with them.

Participants rated the sexual desirability of their potential "partner" on a 5-point scale ranging from 1 (not at all sexually desirable) to 5 (very much so). The data shows that study participants perceived the potential partner as more sexually attractive in the certainty condition (here the mean of the insider's sexual desirability was 3.15) than in the uncertainty condition (where the mean of the insider's sexual desirability dropped to 2.73).

The answer is clear -- sexual desire thrives on reduced uncertainty.

While studies one through four examined the uncertainty effect on single adults, studies five and six explored whether the effect of uncertainty could be generalized to the everyday lives of long-term partners. Here romantic interest was substituted with perceived partner regard. Again, the researchers found that feeling greater relationship certainty predicted greater desire for sex with one's partner -- which held true for both women and men in a committed romantic relationship.

Of course, uncertainty is more typical of initial romantic encounters when little is known about the new partner, compared to more advanced relationship stages, when the certainty about a partner's commitment and intentions is relatively high. When uncertainty about a partner's interest emerges in an established relationship, it clashes with the need for security that long-term relationships typically provide. Birnbaum says uncertainty "may therefore be particularly threatening and devastating for personal and relationship well-being in established relationships, in which it is least expected."

The studies build on the age-old debate as to whether or not knowing a partner's (or potential partner's) romantic interest increases or decreases their sexual desirability -- essentially the question of whether "playing hard to get" makes one more successful in the dating arena.

Do the findings put the debate finally to rest?

"Well, they don't put the final dagger in the heart of this idea, but our findings do indicate that this idea is on life support," says Reis, noting that the uncertainty idea was "never supported by solid science -- but folk wisdom at best."