The research is fairly unclear regarding whether women experience qualitatively different types of orgasm. Research has shown that perhaps different contexts or stimulation of different sites may lead to a change in the intensity of orgasm, but very limited research has demonstrated difference in the physiological response associated with different types of orgasm.

Well, new research published in the Archives of Sexual Behavior found that when 265 women were asked about their orgasmic experience, they identified two distinct types of orgasm, to which the researchers, King and Belsky (who also has a blog on Psychology Today), named "surface" and "deep" orgasms.

The research was framed from an evolutionary standpoint, where different types of orgasm may have different adaptive significance, which is worth mentioning in order to put into context some of the interesting findings.

One evolutionary line of reasoning regarding the female orgasm is related to the existence of what's called "orgasmic insuck". This idea is at the core of the evolutionary claims around orgasm as a mechanism of female choice, where women experience a different type of orgasm (one that involves insuck) when with an evolutionarily-speaking preferred partner. Insuck is thought to help explain why only some types of orgasm have an adaptive significance.

Insuck is a pressure change between the vagina and uterus that involves a peristaltic action and allows females to preferentially select sperm from their male partner. And insuck doesn't just happen in humans. Insuck has been found to occur in other mammals such as rats, cows, dogs, horses, rabbits, and macaques, lending more support to it being an adaptive function.

The study I mentioned earlier by King and Belsky was conducted to test the proposition that there are different kinds of female orgasms, to see if women could tell the difference when experiencing characteristics associated with insuck (such as internal sucking sensations), and to extend this by determining whether certain partner characteristics and behaviors are different depending on the type of female orgasm experienced.

As I mentioned, King and Belsky found that women did describe two qualitatively different "types" or orgasm: "surface" and "deep". Additionally, they found that "deep" orgasms were associated with internal sensations similar to those experienced with the occurrence of insuck. The partners who the "deep" orgasms occurred with were perceived to be considerate, dominant, have a notably attractive smell, and provided firm penetration. So the male partners of women who experienced "deep" orgasms did demonstrate some of the evolutionarily relevant characteristics to support "deep" orgasms as an evolutionary trait.

Keep in mind, the researchers asked the women to recall their subjective experiences. There were no physiological measurements taken. Additionally, women were asked if they felt specific physiological reactions such as "internal sucking sensations" in order to attempt to measure insuck. What's interesting about this is that most women can't even match their level of subjective arousal to their level of physiological arousal based on genital response. Therefore, I find it hard to believe a woman would be able to accurately distinguish an "internal sucking sensation" from any other physiological experience during an orgasm using a recall method.

Regardless of this limitation, an important take-away from this study is that we still have severely limited knowledge when it comes to the female orgasm.

Additionally, although there is not one way to experience orgasm, creating any sort of hierarchy of orgasm is not beneficial. Women experience orgasm differently from one another, and perhaps this experience is also different depending on the context. Using self-reports from women is limiting if the intent is to categorize, because we don't know if one woman's idea of "deep" is the same as another woman's idea of "deep".

The authors of this study suggest that sexual passion between partners is a non-accidental component of sexual functioning that has too frequently been missing in research, and I couldn't agree more. This study contributes one piece to the incredibly complicated puzzle of female orgasm that is still missing a lot of pieces.