The Brain in Love: 12 Lessons to Enhance Your Love Life by Daniel G. Amen

and being “in love” when you have regular sex for several reasons. First, the skin is sensitized by oxytocin, encouraging affection and touching behavior. Then, oxytocin levels rise during subsequent touching and eventually even with the anticipation of being touched. Oxytocin increases during sexual activity, peaks at orgasm, and stays elevated for a period of time after intercourse. This may also be why men are more likely to talk and feel emotionally connected after sex. In addition, there is an amnesic effect created by oxytocin during sex and orgasm that blocks negative memories people have about each other for a period of time. The same amnesic effect occurs from the release of oxytocin during childbirth, while a mother is nursing to help her forget the labor pain, and during long, stressful nights spent with a newborn so that she can bond to her baby with positive feelings and love.
    Higher oxytocin levels are also associated with an increased feeling of trust. In a landmark study by Michael Kosfeld and colleagues from Switzerland published in the journal Nature , intranasal oxytocin was found to increase trust. Men who inhale a nasal spray spiked with oxytocin give more money to partners in a risky investment game than do men who sniff a spray containing a placebo. This substance fosters the trust needed for friendship, love, families, economic transactions, and politicalnetworks. According to the study’s authors, “Oxytocin specifically affects an individual’s willingness to accept social risks arising through interpersonal interactions.” The scientists studied oxytocin’s influence on male college students playing an investment game. Each of fifty-eight men was paid $64 to participate in the experiment. The volunteers were paired up, and one man in each pair was randomly assigned to play the role of an investor and the other to play the role of a trustee. Each participant received twelve tokens, valued at thirty-two cents each and redeemable at the end of the experiment. The investors decided how many tokens to cede to the trustees. Both participants, sitting face to face, knew that the experimenters would quadruple that investment. The trustee then determined whether to keep the entire, enhanced pot or give some portion of the proceeds—whatever amount seemed fair—to the investor. Among the investors who had inhaled oxytocin, about half gave all their tokens to the trustees, and most of the rest contributed a majority of their tokens. In contrast, only one-fifth of the investors who had inhaled a placebo spray forked over all their tokens, and another one-third parted with a majority of their tokens. Oxytocin influenced only the investors. Trustees returned comparable amounts of money after inhaling either spray. The trustee responses were generous when the investors offered most of their tokens and were stingy when the investment was small. The influence of oxytocin was limited to social situations. The oxytocin influence is “a remarkable finding,” says neuroscientist Antonio Damasio of the University of Iowa College of Medicine in Iowa City in an editorial published with the research report. Damasio had previously argued that the hormone acts somewhat as a love potion. “It adds trust to the mix, for there is no love without trust,” he says.
    Bonding chemicals can also enhance fertility. Increases in oxytocin have enhanced fertility in some studies in animals. In humans, increased oxytocin levels are associated with decreased stress levels and increased trust, both of which are likely to enhance conception.
    Vasopressin
    Other clues to male commitment come from new research on the hormone vasopressin. This chemical is involved in regulating sexual persistence, assertiveness, dominance, and territorial markings. Not surprisingly, it is found in higher levels in the male brain. Why do some men constantly live with the discomfort of a wandering eye, while others remain content with fidelity? The