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Men are often taught to make the first move, push for the first kiss, and initiate ever-higher levels of sexual intimacy with a woman. This type of pressure to make the first move can feel onerous. But research shows that it is women who typically signal whether a man can make an approach in the first place — initiating the entire process.

Drawing from work on interactions among nonhumans, primarily birds, researchers in the 80s and 90s documented early courtship behavior in a series of creative observational studies conducted in bars, dance clubs, and other places where people meet. These researchers carefully tracked the nonverbal strategies used to signal sexual interest (see Moore, 1985; Perper, 1985; Walsh & Hewitt, 1985).

They consistently noted that women signaled men who interested them, helping to ensure their approach.

What are the nonverbal behaviors that women engage in to signal their interest in a particular man? Here was a typical scenario: A woman walks into a bar with some of her friends. She engages in a long, steady scan around the room, ultimately fixing her gaze on a man she finds attractive. Gaze is important here, and a key component of signaling interest. The woman maintains an extended gaze at the man until he notices her, she smiles, then she breaks the gaze, returns the gaze again, smiles, and again breaks the gaze. A woman interested in a man then might primp or self-groom, fixing her hair a bit, adopting an open body posture (e. ., arms away from the body), or starting to orient her body to face him.

Once he approaches (as he almost always does) both orient their bodies toward each other, and the woman may engage in other nonverbal behaviors, such as palming (displaying an open wrist and palm), self-touching (such as a breast graze), or exposing her neck, perhaps by leaning back or canting her head.

Once you know to look for these behaviors, you can see them all the time. Two newly acquainted people who are sexually interested in each other will show increasing synchrony in their gestures and movements, light touching (especially by men), smiling, leaning forward, and head tilting. Women may even notice belatedly that they find someone attractive by observing themselves self-grooming a little when an attractive man enters the room.

Research on other cultures finds similar behaviors: An eyebrow flash combined with a smile was a common signal in a range of cultural backgrounds, from the Balinese to Papuans, French, and Wakiu Indians (Eibl-Eibesfeldt, 1971).

What’s really intriguing, however, is that although most women could describe some aspect of this signaling process, men often were unaware that they had in fact been signaled by the woman they approached—thinking instead that they simply had the initiative to approach an attractive woman.

Trained observers have been able to predict to a startlingly high degree of accuracy the outcomes of interactions between women and men based on women’s nonverbal signaling behaviors alone (see Moore & Butler, 1989). One of the best predictors of who would be approached was signaling frequency: High-signaling women of average were much more likely to be approached than low-signaling, beautiful counterparts. In addition, the rate of signaling on the part of women was strongly correlated with how much interest they elicited in the men (Grammer, Honda, Juette & Schmitt, 1999).

Some men mistakenly approached a woman who had not signaled them, but they were typically shut down quickly. Researchers describe these individuals as having poor "decoding" abilities. Women have an equally impressive array of nonverbal shut-down behaviors, such as leaning away, crossing their arms over their chest, avoiding eye contact, and negative grooming behaviors, such as picking one’s teeth — the mirror-opposite of signaling behaviors (Moore, 1998). Unfortunately, men often were worse at picking up rejection signals, judging them to be weaker forms of communication than women intended them to be (Moore, 2002).

These field studies typically used evolutionary theory as a conceptual framework, so the focus tended to be on men and women’s courtship behaviors. However, other researchers have found great similarity between the behaviors used by women signaling their sexual interest in men and women signaling their sexual interest in other women (Rose & Zand, 2002).

There is a lack of more current research on signaling and more generally. Yet flirting is important for conveying initial interest in a potential partner, as well as maintaining interest in an established relationship. Men tend to view flirting as more sexual and instrumental than women do; women tend to view flirting as more fun and relational (Henningsen, 2004).

Current applications in this line of research have become narrower, focusing to a great extent on eye gaze as a metric of sexual interest vs. (Bolmont, Cacioppo, & Cacioppo, 2014). (Spoiler alert: Subjects spend more time looking at the face when making decisions about love, but more time looking at the body when making decisions about sexual desire.)

Neurophysiological research has found that mere eye contact with an attractive person activates reward-related brain areas and prompts approach. Flirting and expressing interest in initiating a relationship now rely heavily on written forms of communication in new digital technology environments.

We may be spending ever-increasing hours meeting new people through our virtual worlds, but ultimately, we connect face-to-face and rely on our nonverbal behaviors to convey far more than words alone can do.