All the while, a significant body of opinion has suspected that the final answer will not be quite a simple as that. As more and more information comes in, it is beginning to look as if there are multiple factors, with the more important ones inborn. But post-natal factors may play a part in how a person's sexuality is expressed.

As discussed in many previous articles in Yawning Bread, "inborn" doesn't equate with genetic causation. Yes, genes probably play a part as some research have shown, but the most fascinating of the latest research concerns the role that hormones play in organising the foetal brain. The neuronal architecture of people's brains are not all alike. There seems to be differences between male and female brains, hetero-and homosexual brains. The way the person responds to stimuli (e.g. erotic stimuli), or the way one processes one's emotions, is dependent on the way the brain is wired.

In contrast, there is much less known about post-natal influences. To date, no particular factor has been demonstrated to have an effect on a person's sexual orientation. The best one can say is that post-natal influences have not been eliminated as possible factors. One or more may still be proven to be a factor. However, chances are that even if such factors are found, they are likely to merely modulate a person's sexual orientation rather than determine it. The neurological architecture that each person has determines the range of possibilities for him; post-natal socio-environmental influences may fine-tune his choices within those possibilities.

Take, for example, in the very simple case of men who are 100% gay, i.e. who are exclusively attracted to men. But the type of men they are attracted to -- whether beefcakes or princesses, hairy or hairless -- may be something they acquire post-adolescence.

As another example, take men who are 100% heterosexual. To what extent are they able to appreciate male beauty; to what extent are they able to perform homosexual sex even if their heart is not in it? To what extent do they revel in homo-social bonding even if things don't quite get as far as the physical? One suspects that post-natal and post-pubertal influence may have a role to play. Their inborn conditions will never make these heterosexual men a "6" on the 7-point scale, but the socio-environmental effects may make the difference between a "0" or a "1".

Basically the war between the "choice" and "inborn" positions is winding down. The pure "choice" argument is essentially lost with diehards confined to the fundamentalist churches who anyway dispute that evolution ever occurred. Concern for empirical science is not one of their strong points.

Even in those quarters, some are beginning to concede that there is such a thing as homosexual orientation, though their platform is that if an individual "suffers" from it, he should do his utmost to "turn away" from it, preferably through prayer. At least be celibate, they say.

But this prospective "victory" for science is not as simple as it looks, for in a strange way, the "choice" argument lives on, particularly among lesbians and bisexuals. The fact that for so long the argument has been reduced to a simplistic dichotomy between "everybody is heterosexual, but some choose to be deviant" and "your sexual orientation is inborn" is really a reflection of the way the male voice has dominated the debate, on both sides.

It's a complex issue, but this essay will take a peek at what it's about.

 
Genital arousal

First, let me introduce the term "penile plethysmography". It's a way of measuring the engorgement of the penis as a man gets genitally aroused. It is done through a simple cuff around the penis, and has been used widely since the 1950s when it was invented by Kurt Freund, a Czech physician. In the early days, it was used to ferret out homosexual men in order to bar them from military service, but lately, it has been used primarily for scientific research. With the large amount of data collected over the years, it is considered a reliable measure.

Usually, the cuff is used in conjunction with videos. The subject wears the cuff and is given a variety of short videos to watch. Typically, in any experiment, the subject (in a private cabin) watches male-female sex, male-male sex and female-female sex, interspersed with non-sexual sequences, e.g. scenery or animals.

For women, the photoplethysmograph was invented in 1975. It's shaped like a tampon and is meant to be inserted into the vagina. It emits light onto the vagina wall and measures the amount of light that is bounced back. The theory is that as blood flow to the vagina increases in response to sexual arousal, the colour of the vaginal wall changes, just like how pallid cold skin is a different colour from hot-flushed skin.

Like male subjects, the women are given videos to watch while the photoplethysmograph measures what is happening "down there".

Typically, subjects are asked prior to the lab assessment, to complete a questionnaire about their sexual preferences and activities. Some very interesting results are emerging from various studies about the way these self-reported profiles correlate with or conflict with the lab measurements.

In a 2004 paper it was reported that men's self-reports correlated very well with their plethysmograph readings. Heterosexual men responded most strongly to watching female-female sex, and least to male-male sex. Homosexual men responded most strongly to watching male-male sex, and least to female-female sex. Almost all respondents' penises confirmed their sexual orientation as declared on the questionnaire [1]. The correlation was generally very good.

For the women, the findings were quite different. Arousal patterns for heterosexual women were remarkably similar to arousal patterns for homosexual women. Generally, for both straight and gay women, the photoplethysmographs registered vaginal arousal for all kinds of sex scenes, more or less equally, but seldom strongly. It appeared that women found the various kinds of sex stimulating to roughly similar degrees. This was strikingly different from the men's results, where straight men and gay men had totally different bell curves.

Secondly, 37% of the women had photoplethysmograph readings showing their strongest arousal opposite to their declared sexual orientation, that is to say, over a third of the heterosexual women, for instance, showed higher readings of arousal watching lesbian sex than any other kind.

So much for gay and straight, what about those who declare themselves bisexuals?

 
Bisexuals and fluidity

Kurt Freund, the man who invented the penile plethysmograph, said that his "many investigations over more than 25 years led him to conclude that, though some [men] may engage in physical activity with both sexes, very few actually show physical erotic responses to both."

Men who declare themselves bisexual mostly show a penile response indistinguishable from gay men's. This and Freund's statement were reported in the book 'The Sexual Rainbow' (2003), by Olive Skene Johnson.

I am aware that such a claim is a scalding hot potato. In mid 2005, the New York Times published an article about a recent study by Michael Bailey making the same claim. That article raised a storm of protest accusing Bailey of trying to "erase" bisexuality. In addition, many opponents pointed to Bailey's ethical lapses in some other research pertaining to transsexualism, thus questioning his credibility overall. I won't go into that argument here (because it is tangential to the thrust of this essay), except to point out that Bailey was hardly the first person to report such findings pertaining to male bisexuals.

I'm more interested in bisexual women. In her book, Johnson gave a concise review of the situation with respect to them. "One of the most curious findings about bisexuality is that it appears to be much more common among women," she wrote.

Furthermore, "for women, bisexuality is a stable orientation." Quite often, men who label themselves bisexual tend to change that label this way and that over time; women, less so. Women seem to be more sure that they are bisexual. Why, we'll examine in a minute.

Now, changing subject a little bit, a closer look at lesbians also shows up an interesting difference from gay men. In fact, one of the first things I regularly try to disabuse gay men of, is the notion that lesbians are mirror images of gay men.

A 2000 study by psychologists Lisa Diamond and Ritch Savin-Williams found that two-thirds of lesbian women reported experiencing periodic attractions to men.

On the other hand, women who didn't see themselves as lesbian sometimes reported same-sex involvement. For them, one of the most common triggers was an intense, emotionally intimate relationship.

How many straight men would say they sometimes got into a gay relationship through intense emotional attachment? How many gay men would say likewise but vice versa? I think it's a pretty rare thing among men.

Men seem to get into relationships via physical attraction. It's what propels them to approach the girl, or the guy. Very often, it's just for sex and goes no further (though straight men are conditioned by our culture to protest their love in order to justify the sex), but sometimes, the erotic attraction (which may not be immediately fulfilled) leads to a relationship.

Some lesbians too are driven mainly by erotic interest, but it is quite striking how many studies show that a substantial number speak of getting to know the person first, before the question of sex arises. This is also a frequent observation made of straight women.

There seems to be a fluidity that is more apparent among women, straight and gay, than among men.

Another clue lies in how men and women fantasise about sex. It's a well-known fact that for women, the fantasy often involves a specific person with a face and a personality, at least an imagined one. Most times, it's an actor or pop star [2].

Men, on the other hand, tend to fantasize about having sex without putting a face or name to the imaginary partner. The body is imagined more than the personality.

All these differences have consequential effects on how we speak of sexual orientation.

 
Two kinds of sexual attraction

James Weinrich of the University of California, San Diego, has postulated that there are two kinds of sexual attraction: romantic and physical. Men and women may be giving different weights to these two kinds of attraction.

Considering what I have outlined above, it would seem clear that men are more driven by physical attraction. 

Women, on the other hand, have a greater tendency to put more weight on romantic attraction. The personality of the partner, the emotional connect, is critically important in order to trigger or sustain sexual interest. 

The problem this presents is that unlike physical bodies, personalities and emotional consonance do not differ that greatly between men and women. Just as there are humourous, sensitive, cat-loving women, so there are humourous, sensitive cat-loving men.

Hence, if a person is predisposed to looking first at personality and emotional intimacy as a trigger for sexual interest, then it can get pretty confusing. Sometimes the person of interest is male, sometimes she is female. So, does that make one straight or gay?

This probably explains why women tend to be uncertain (compared to men) whether they're straight or gay, since the answer is far more situational than the case with men's sexual interests. This probably also explains why a larger number of women, as they get older and look back on a lifetime of partners, are surer that they're bisexual.

This is not to say there aren't any "true" lesbians. Of course, there are. There are women who, even if they're looking for emotional bonding before physical attraction, are predisposed (inborn again) to find it only in other women. The whole idea of dating a man and having sex with him is repulsive.

On the other hand, there are men whose sexual interest is first triggered by emotional affinity rather than big boobs, tight buns or pretty faces. Some may be open to developing emotional affinity and sexual interest with both males and females (thus bisexual), while others can't conceive of any romance with women (thus pure gay).

Human variety is quite wide, and while in the above, I speak of "generally" or "tend to", some men and women do overlap in their characteristics. For example, men are generally taller than women, but it doesn't mean that all men are taller than all women. So while I say women tend to get to erotic attraction indirectly via romantic interest, it is only relative to men's tendencies, and should not be taken as a dogmatic statement applying to all women. Ditto when I say men look for sex first before love, it doesn't mean every last man is like that.

 
When indirect, there may be a little choice

The male conceit is to think that everybody experiences sexual orientation the way that men generally do, that is, by knowing full well how our brains and genitals respond to physical attraction. There are people out there, disproportionately women, whose sexual interest is triggered by the specific person, not the sex or the objectified anatomical attributes.

For this group of people, asking them "Are you primarily interested in males or females?" may seem a rather strange question. For them, it all depends on the person of the moment. For some women, that person somehow is always male, so they know they are straight. For some women, that person somehow is always female, so they know they're gay. For a significant number of women (and a much smaller number of men), that person is sometimes male, sometimes female.

In such circumstances, the "choice" issue arises again. She can choose to turn away from one woman and hope that the next person of interest turns out to be a man.

For gay men and women, there is still no choice. Even if he or she turns away from one lover, the next lover is still going to be the same sex.

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