Many a woman will tell you that her taste for sweet and stodgy foods varies according to her menstrual cycle. But now, researchers announce that there could be another preference that varies in line with womens’ monthly hormonal fluctuations: their taste in men: or, to be more precise, their taste in men’s faces, say Ian Penton-Voak of the University of St Andrews, Fife, UK and colleagues. Penton-Voak’s group, who last year announced that, on the whole, women prefer more ‘feminine’ male faces, now report in the 24 June issue Nature that there are times of the month when they actually prefer ‘masculine’ Clint-Eastwood types over more ‘feminine’ Leonardo-DiCaprio lookalikes.

The team questioned British and Japanese women as to which of a series of computer manipulated ‘average’ Caucasian and Japanese faces they found attractive. The women seemed to prefer more masculine male faces when they were in the middle of their menstrual cycle and hence most fertile. Just before, during and just after menstruation, on the other hand - that is to say, when they were least likely to conceive - the subjects were drawn to feminine male faces. A ‘control group’ of women taking the contraceptive pill , who were therefore not influenced by oestrogen/progesterone cycling - showed no such fickleness, and stuck by their taste in softer-faced men.

Interestingly, the researchers found that this capriciousness was more marked when women were asked to pick the “most attractive face for a short-term sexual relationship”. When choosing for a fling, it seems, women opt for hunkier men even though they (in other studies) describe this physical type as less dependable, dishonest and ‘cold’. When they were given the task of choosing Mr Long Term, however, their preference for ‘feminized faces’ - faces which previous research has shown are associated with better parenting and fidelity - showed more stability.

The researchers speculate that whereas females might choose a reliable, but not necessarily genetically optimal primary partner, they might, “when conception is most likely, pursue extra-pair copulations with males with a more masculine appearance” - males who, statistics show, have stronger immune systems. In other words, these cyclic preferences might be - in evolutionary terms, at least - allowing women to get the best of both worlds: a happy home and healthy children to put in it.