Psychology Today: A Wink and a Smile:
"Men, don't assume that a new woman likes you simply because she listens to you. In fact, her 'come hither' signals may be misleading. That's the conclusion researchers at Vienna's Ludwig Boltzmann Institute of Urban Ethology reached. In their study, appearing in the journal Evolution and Human Behavior, 45 male-female pairs of strangers who thought they would be rating videos suddenly found themselves alone when the experimenter left to take a phone call.
For 10 minutes the couple's interactions were secretly recorded and then examined for women's 'courtship' signals such as hair-flipping and head-tossing. 'Rejection' signals from both parties, such as avoiding conversation, were also measured, along with how much each person spoke. Later, each participant rated the other's attractiveness and their own interest level in dating that person.
'One of the surprising facts in this study was that women do not send clear rejection signals,' write the study's authors, led by Karl Grammer, Ph.D. 'A woman sends sexually explicit signals without having much interest in the man.' This behavior may encourage men to reveal more about themselves, the authors suggest, allowing women to verify their initial impressions. What's more, women used subtle signals such as nodding to direct the flow of conversation, and they avoided contact with men only if the men talked too much initially."