Until reading this book, I didn’t know how much of our behaviors are shaped by the chemistry in our brain, especially the ones between the sexes. Many kinds of our bodily chemicals are introduced here: oxytocin, dopamine, vasopressin, tosterone and etc. I learned a lot about the sexual behavior of animals like Angler Fish, Bonobos, and etc. This is a very interesting book. In a way, it ruined my perception of love but it explains a lot of our human behavior between sexes. We owe a lot to our human evolution that shapes our brain to propagate our species. Most of time it’s above our “free will.” This is an excellent book if you’re interested in how the various chemicals affect our brain.
A short summary is here:
Chapter 1: Building a Sexual Brain
The story of machihembra was the first I read about. Interesting that girls turn into a boy at twelve years old in Dominican Republic. Society does not make sexual gender. Boys and girls are made differently started in the brain, not dictated by socialization nor the genitals which they’re born with.
Chapter 2: The Chemistry of Desire
Estrogen or production of progesterone receptors during ovulation (in estrous) puts animals (mouses, cats) and women in heat or more receptive to mating. Testosterone drops when men are near their babies or losing a sports match. It rises when encountering another ovulating female, also more mate-guarding behavior.
Chapter 3: The Power of Appetite
Our appetite is based on MPOA (medial preoptic area), nucleus accumbens, the amygdala, and the VTA. Dopamine hits D1 receptors of MPOA, we become attentive to sex-related cues. MPOA directs the parasympathetic nervous system to send blood to the genitals, creating erections in males and clitoral engorgement in females. VTA transmits dopamine into the prefrontal cortex (disinhibiting sexual desire and giving us tunnel vision for cues that lead to satisfying the desire. After orgasm, Endocannabinoids, the brain version of marijuana, make use a little sleepy. Serotonin gushes, inducing a feeling of calms, satiety, and satisfaction. Endorphins floods into the limbic system and hypothalamic area. Fetishes or partner preferences can be developed from early sexual experience due to satisfying the specific appetite via dopamine release.
Chapter 4: The Mommy Circuit
Oxytocin causes contraction for giving birth and induces maternal behavior. Prolactin stimulates the breasts to make milk and stimulates the MPOA, which signals the amygdala to suppress the fear and cause the mother to be calmer. Dopamine rewards the mothers for caring for their children.
Chapter 5: Be My Baby
Prairie voles (Monogamy, mated for life) vs. Meadow (Polygamy) voles. More oxytocin receptors in the accumbens, reward center in the brain, are seen in the Prairie voles. Bonding takes all oxytocin, dopamine, opioids, and good social memory (recognizes faces/smell) with the partner when the feel-good cocktails are released. Couples when nose sprayed with oxytocin (or having the vaginal-cervical stimulated as in sheep) tend to be exhibit more “positive” behavior/communication toward each other and create the bond. “A man is a woman’s baby.”
Chapter 6: Be My Territory
Vasopressin in males stimulate territory guarding behavior. Switching on the avprla gene makes the male meadow voles monogamous and good bonders due to increase of Vasopressin receptors. “A woman is an extension of a man’s territory.”
Chapter 7: Addicted To Love
Drug addiction is parallel to falling in love.
Vasopressin serves as a chemical trigger (like in a loaded rifle) in the CRF system to fire off the HPA axis during separation from partner or drug in an addict. For humans, “falling in love is like putting a gun to your head.”
Chapter 8: The Infidelity Paradox
Normal self control, your prefrontal cortex’s talk with your amygdala, ventral tegmental area (VTA) and accumbens, said “cut it out!” before cheating takes place. Once married/bonded, male’s testosterone and stress hormone drops, hence having less sex. This is a phenomenon named after Calvin Coolidge: slow death of passion experienced by many human couples, and rejuvenation of sexual appetite and performance by lure of novelty and infidelity. There is a D4, cheating gene, associated with human ability to resist impulsive desire or yield to temptation.
Chapter 9: Rewriting the Story of Love
Knowing how all the various chemicals work in our brain, do we feel we still have the free will or are we puppets of those “drugs” inside our brain. Is love induced by a drug still a love, real and true? That’s the difficult question.