Men and women are different. Their “sexual engine” makes different use of the accelerator and brake. Author, sex researcher, and professor of women’s sexuality, Emily Nagoski, calls this the “dual control model” (Come As You Are, 2015). This model explains aspects of the biological and psychological difference between male and female sexuality and what we need to know to have sexual self-confidence and empathy for our partners.

Accelerator vs. Brake

The central sexual response mechanism in the brains of men and women consist of two universal components – a sexual accelerator and a sexual brake.

This dual control model consists of two parts:

1. The Sexual Excitation System (SES) or “accelerator” of sexual response receives information about sexually relevant stimuli in the environment. It sends signals from the brain to the genitals to “turn-on”. The SES constantly scans the “context” (including thoughts and feelings) for things that are sexually relevant. With the SES, anything you see, hear, smell, taste, or imagine might send a “turn-on” message.
2. The Sexual Inhibition System (SIS) is the sexual “brake.” This system notices all potential threats in the environment (such as STI transmission, unwanted pregnancy, social consequences of sexual activity) and sends signals to “turn off”. Nagoski calls this the sexual “foot brake.” It is primarily associated with the fear of consequences. There is also a second brake, more akin to a handbrake, associated with a fear of performance failure, like worry about not having an orgasm. “If you try to drive with the handbrake on,” says Nagoski, you might be able to get where you want to go, but it’ll take longer and use a lot more gas” (Come As You Are, p. 49).

For Arousal — Activate the Accelerator and Deactivate the Brake

Arousal (psychological desire) happens with activation of the accelerator and deactivation of the brake. The former is more salient for men, the latter more important for women. Male sexuality is accelerator-dominant because the SES scans for female attributes that are cues of fertility. The SES (in men) is the pursuer and the initiator. Women’s brake system comports with the evolutionary agenda for a cautious choice of a mate and a need for safety.

Accelerator and Brake in the Brain

Differences in brain structure between men and women are related to the male-dominant accelerator system and the female-dominant brake system.

Men, in general, have a higher baseline of activity in the older part of the brain, the limbic system, which makes them particularly alert during the first stage of seduction, according to Marianne Legato* (Why Men Die First). The medial preoptic area (MPOA), found in the hypothalamus, is related to sexual pursuit and is 2.5 times larger in males, according to neuropsychiatrist Louann Brizendine (The Male Brain). Men also show greater activity in the visual cortex when perceiving erotic pictures, reflecting a gender-specific visual mechanism for sexual selection.

Female Amygdala is More Sensitive to the Fear of Consequences

The brain’s danger and alert system is the amygdala. While larger in males, the female amygdala seems to be more sensitive to the fear of consequences descriptive of the braking system.

Brain’s Worry Center is Bigger in Women

Another part of the brain, the anterior cingulate cortex (ACC), is also involved in “braking.” According to Brizendine, the ACC is the worrywart, fear-of-punishment area, and center of sexual performance anxiety. It weighs options, detects conflicts, and motivates decisions. The ACC is also the area for self-consciousness (the “handbrake”). The ACC is bigger in women. In addition to a less active ACC in men, testosterone decreases worry about punishment and reduces the strength of a sexual brake and fortifies the sexual accelerator.

Women Put On the Brakes

For women, in both ancient and modern times, safety is a powerful need that activates the sexual brake: fear of being killed, being raped, getting pregnant, and/or having their reputation destroyed. A woman’s deepest unconscious fear is that a man will rape or kill her. (A man’s deepest unconscious fear is that a woman will sexually humiliate him.)

Sexual Temperament Questionnaire

According to Nagoski’s research using her “Sexual Temperament Questionnaire,” 50-65% of women have a moderately strong inhibition system (SIS). Any increase in stress (anxiety, overwhelm, exhaustion) will reduce interest. And, 25% of women have a “high” SIS or a very strong braking system. These women are sensitive to all reasons not to be aroused and have more sexual problems than women with less active SIS. Nagoski says low female desire is not about hormones or boredom with monogamy; it is most likely about stress, depression, anxiety, trauma, attachment, relationship satisfaction, and lack of self-compassion. [Other researchers say boredom and lack of novelty do affect female marital desire.]

SES and SIS Operate Independently

The sensitivity of the SES and SIS are individual traits. Both can be sensitive, both can be not sensitive, and one or the other can be sensitive and not sensitive, co-existing together. (It can get very complicated!) But the general differences of dual control between men and women directly affect their sexual relating and sexual psychology. These differences are congruent with evolutionary theory and mate selection science.

Asexuals Have Essentially No Sexual Excitation System

A fairly weak accelerator (independent of brakes) is one predictor of asexuality – people who do not desire sexual contact. In studies of self-identified asexuals, researchers found asexuals had significantly “less accelerator” activity than their sexual counterparts (Prause and Graham, 2007**). Nagoski posits that part of the cause of asexuality as a sexual orientation for women is that their brains do not notice sexually relevant stimuli. Nagoski says asexuals represent only about 1 percent of the general population. Whereas, about 5-10 percent of women score as having low SES on the Sexual Temperament Questionnaire.

Why is it Important to Understand the Sexual Accelerator and Brake?

Men and women have differences that we must acknowledge and understand to have fulfilling romantic and sexual relationships.

A difference in the level of desire is the single most common sexual dysfunction for couples. Usually, that dysfunction includes a belief by one partner that their level of desire is better or is the way it “should be.” Nagoski suggests it is not the differential in desire that causes the dysfunction but how the couple manages it. The problem isn’t desire itself; it’s the context. What is needed is more sexually relevant stimuli activating the accelerator and fewer things hitting the brake.

Advice for Couples

Good advice to couples is to focus first and foremost on the operation of her “brakes.”  What is the right context for romance and sex; what context for sexual expression takes her foot off the brake? What are the sources of her stress, anxiety, and relationship dissatisfaction? What trauma is still unexamined and unresolved? What triggers her handbrake — body image concerns or worry about orgasm? The to-do list in her head?

Nagoski has a helpful worksheet in Come As You Are to identify and list the “not-so-sexy” inhibitory contexts (as well as a worksheet for situational accelerators) in the following categories: mental and physical well-being, partner characteristics, relationship characteristics, other life circumstances, and the sexual activities practiced.

Conclusion

The composition of our excitation and inhibition systems is set by our biology, life experiences, and habits. Creating the right balance of acceleration and braking for any person or couple is more art than science, and probably hard work. Again, these are individualized sensitivities. But there is no substitute for giving your partner understanding, acceptance, and compassion. Start with how men and women are generally different and what part of that difference is true for you as a person and a couple. Let’s refuel that engine with the right contexts and get it back on the road at the right speed.

Notes

See blog: Spontaneous and Response Desire — the Underbelly of Heterosexual Mating and future blogs on the importance of context for women.

*Marianne Legato is an internationally renowned academic, physician, author, lecturer, and pioneer in the field of gender-specific medicine. She is Professor Emerita of Clinical Medicine at Columba University and founder of The Partnership of Gender-Specific Medicine.

**Prause, N. and Graham, C., “Asexuality: classification and characterization.” Archives of Sexual Behavior 36, 2007, p. 341-56).

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