When asked about sexual orientation, most people typically identify the categories: straight, gay and bisexual. We tend to place people into the straight category if they are in relationships with opposite-sex individuals, in the gay category if they are in relationships with same-sex individuals and into the bi- category if they pair with members of either sex. However, sexual orientation is much more complex than simply who one is in a relationship with. In fact, sexual orientation, the different expressions of it, what determines it, how it is defined and how it may change over one's lifetime, is a puzzle. This summer, approximately 60 international researchers met in Lethbridge, Alta., to share the latest findings at the Puzzle of Sexual Orientation Conference. I learned a few new things that you might find interesting (and surprising!).

Research tracking the sexual attractions of men and women over many years has found that many people experience fluidity in their sexual attractions. Sexual-orientation researcher Dr. Lisa Diamond has followed women's sexual preferences over a number of decades and she has found that sexual preferences, attitudes, behaviours and identity are malleable to some degree, depending on their immediate situation or environment. For example, an individual who identifies as a lesbian at one point in time may identify as bisexual at some time in the future. Although researchers are now studying the factors and contexts that lead to this fluidity, it is clear that (at least for women) attraction to a particular individual, regardless of gender, may be more important for predicting whom one chooses to be in a relationship with, than that person's gender. So, if a woman is attracted to and wants to be in a relationship with a particular woman, she may be more likely to identify as a lesbian at that point of time than if she were attracted to (and in a relationship) with a man.

There also seems to be consensus on the finding that, at least for most women, a genital response to a certain person or sexual image will not tell you about that person's sexual orientation. Sex scientists measure sexual response in a laboratory to gain insights into patterns of sexual arousal. For readers watching the third season of Showtime's Masters of Sex, they will have a better sense of what I am referring to, since the TV series depicts sex researchers Masters and Johnson measuring how the body responds during sexual activity. For women, their body's sexual response can be measured with a vaginal photoplethysmograph (a tampon-like probe that women insert before watching erotic films). Women who are sexually attracted to men show the same arousal response whether they are watching an opposite-sex or a same-sex couple engaging in sex. Dr. Meredith Chivers of Queen's University is studying this phenomenon in women of different sexual orientations and her research concludes that, for women, the presence of a physical response does not tell you anything about her sexual attraction or her sexual orientation. Rather, women's ability to lubricate to sexual triggers seems to be an evolutionarily evolved automatic response.

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Dr. Lori Brotto is an associate professor of gynecology at the University of British Columbia and a registered psychologist. You can find her at brottolab.com and follow her on Twitter @DrLoriBrotto.