When a man meets a friendly woman, chances are he thinks she’s into him even when she isn’t. (As discussed in BLONDES this evolutionary bias is reversed in women; in fact, we’re more likely to think a man is just not all that into us. It’s especially true now that a certain mantra-like book and movie has drummed the notion into women’s subconscious.)

But can men tell if a woman is into every man she meets, not just him specifically? The answer is yes, according to Tyler Stillman and Jon Maner at the University of Florida. In their latest study, the psychologists asked 24 women to take a questionnaire that measured their sexual strategies, from high restricted (highly selective) to unrestricted (highly promiscuous). Then, one by one, they paired the women up with a “fairly attractive” and charismatic male research assistant and asked the duo to solve a Rubik’s Cube puzzle without talking and using only one hand each.

Later, male and female judges watched videos of the Rubik’s Cube-solvers, paying special attention to the women’s body language as they interacted with the cute guy. When asked to identify which women had promiscuous dispositions, the judges were surprisingly accurate. This might not be so surprising. More interesting are the body language cues associated with high sociosexuality versus those that were not.

While you might think any friendly body language might be interpreted by an unknowing observer as licentious, that’s just not so. It turns out that classic cues such as smiling, laughing, tilting the head, wearing a provocative dress, touching the hair, leaning towards a man with an open posture, are not reliable signals of promiscuity — just friendly flirtation — and even impartial observers could tell the difference. What distinguished wanton women’s behavior from that of their more selective peers were just a handful of cues: eyebrow flashes (frequent raising of the eyebrows for one-sixth of a second), fervid glances, and easy distraction from the task at hand.

In keeping with evolutionary theory, women were even more accurate than men when it came to perceiving whether a woman was an indiscriminate tart. To men, knowing a woman’s sexual disposition is helpful. It’s an opportunity! To women, particularly to jealous types, a licentious flirt represents something even more visceral: a threat.