A new study suggests that flirtatious men are most likely to get lucky when a woman is at the peak of her fertility.
To reach the conclusion, evolutionary psychologist, Dr Edward Morrison, of the University of Portsmouth, asked a group of women to examine various facial expressions.
He found when the women were ovulating they preferred flirtatious expressions, reports The BBC.
Dr Morrison said: "If we wanted to attract someone at the Christmas party, flirting effectively may help."
He added: "An ability to 'read' and interpret the facial expressions and an awareness of what you are signalling with your own expressions could improve your chances of successful flirting.
"It is difficult to define what constitutes flirtatiousness and much of it may be something we perceive without even realising it. "But it seems that in the absence of other cues, the 'social properties' of facial movement influences how we judge attractiveness."
However, Dr Morrison added: "Science is still a long way from discovering the magic formula for what women find attractive in a man."
The study has been published in Archives of Sexual Behaviour.