Straight, bi, or gay. Know the facts about sexual orientation. BeingGirl.com goes to the experts. Here's a little bit of information about the people who wrote this article. Lorna Sarrel received her Master's Degree in Social Work from Columbia and has worked at Yale University for 30 years. Phil Sarrel is a M.D. and Professor of Obstetrics and Gynecology and Psychiatry at Yale University. They have given us some insight on the complexity of our sexual orientation that we'd like to share with you. We are sexually complicated beings. Many girls and women have always felt that they were attracted only to guys and that is how they will continue to feel all their lives. This is called being entirely heterosexual, and it is the most common sexual orientation. What makes it kind of complicated is the fact that many heterosexual women have sexual dreams and fantasies about females, sometimes feel attracted to females, and may even have some sexual interaction with a female. Some same-sex "fooling around" is not unusual in the teen years and, for the large majority, this is just a developmental phase. A female who is entirely or mostly sexually attracted to other females is known as lesbian, gay, or homosexual. Interestingly, these women usually report some opposite sex fantasies, attraction, and experience. Women who are about equally attracted to either sex are called bisexual. Just to make things more complicated, a small percentage of women find that they have different sexual orientations at different times in their lives. They usually explain that their sexuality seems to be secondary to love. If they are in love with a guy, they are heterosexual, but when they love a woman they are lesbian. This is probably a kind of bisexuality. No one knows why there are differences in sexual orientation. There are lots of theories about the relative influence of "nature" (genes, hormones, etc.) versus "nurture" (your upbringing and other experiences in life). Many people would like to know whether a person can change their sexual orientation. Those who view it as a learned behavior and a moral choice subject to your will, believe that yes, you can be changed. Those who see sexual orientation as more biologically determined think it is not really changeable and that attempts to change are likely to be psychologically damaging. The bottom line is this: There are no clear-cut answers to many questions about sexual orientation, including the question of whether or not it can be changed. Learn about sexual orientation and read helpful articles at BeingGirl.com.