No, I am not talking about fingering...
A recent study (see article at the BBC News here) of Female Identical Twins, where one twin was straight while the other was a lesbian, found that the gays of the pairs had different sized ring & index fingers on one hand. This is a trait normally found with males rather then females.
Now I am not suggesting that you measure your wife's fingers in her sleep to see if she is a closet lesbian. Haha. While the study is "scientific", it is not a sure-fire way to find predetermined homosexuality in females. So you should only read into this study as a point of interest or as evidence that further studies in this field should be done.
"Bringing Sexual Awareness to the Global Consciousness."
Hahaha. Let me try this one.