FOUR: THE BRAIN BELOW THE BELT
average of one or two : For more on men wanting a greater number of short-term sexual partners, see Schmitt 2001.
interest in one-night stands: For more on one-night stands, see Schmitt 2001, Laumann 1999b, and Mulhall 2008a. For more on men's satisfaction with their sex life, see Colson 2006, who found that almost 70 percent of men reported that they wished to change some things about their sexual life.
men's testosterone levels to go up: Van der Meij 2008.as sexually hot--or not : Ortigue 2008 found that the male brain's decision about desirability of sexual stimuli occurs within the first 200 milliseconds after seeing a woman. This means it occurs before conscious processing.
way their penis is shaped: Sanchez 2007.happy with their partner's size : Lever 2006 surveyed 52,031 men and women and found that many men wished they had a larger penis. And only 2 out of 1,000 men wished their penis were smaller. Dillon 2008 found that penile size is a considerable concern for many men from teens to old age. Wessells 1996 found that neither a man's age nor the size of his flaccid penis accurately predicted erectile length. But stretched penis length most closely correlated with erect penis length. For more on penis size, see Francken 2002.
is their most important feature : Francken 2002 found that a great many men believe that the size of the penis is directly proportional to its sexual power.
larger than it needs to be : Diamond 1997 notes that since the penis only has to be able to fit into a woman's vagina, men with penises that are too large may not be able to sire as many offspring, thus making larger penises undesirable.
from 5.5 to 6.2 inches : Wylie 2007 found that the average erect penis is 5.5 to 6.2 inches long and that an average-sized man is likely to be troubled by concerns that his penis is not large enough to satisfy his partner or himself and to be ashamed to have others view his penis, especially in the flaccid state.
to their females, it's supersize : Diamond 1997 describes that, compared with other mammals, the human penis is larger than necessary.
conscious desire to have sex : Janssen 2008 found in his survey that most men say that they can experience erections without feeling aroused or interested.
to start an erection: Tsujimura 2006. Holstege 2003 found that erection starts as a man imagines having sex with his partner or with other women in any of various positions and locations, both indoors and out. For more on erection, see Janssen 2008, Baskerville 2008, and Schober 2007.
"order for him to function" : Beach 1967 found that none of this circuitry for sexual arousal or erection works in males who are deprived of testosterone. Steers 2000 found that it is testosterone, along with oxytocin and neurochemicals like dopamine, acetylcholine, and nitric oxide, that acts within the brain, spinal cord, and penis to produce an erection. Swann 2003 found that in the male brain, there is a sexually differentiated, testosterone-responsive network that relays signals to the muscle-control areas to produce copulation. For more on intercourse, see Redoute 2005.
men to become fully erect: Miyagawa 2007.the
hormonal engines for erection : Mouras 2008 found
that while being shown sexual video clips, 8 out of 10 healthy men
registered an erection, as demonstrated by a measuring cuff around
the penis.
hope of a sexual
reward: The nucleus accumbens (NAc) is a major center
in the brain for anticipation of reward. For more on sex and
reward, see Ponseti 2009 and Paredes 2009.
one smooth thrust, he was inside: For more on vaginal penetration and condom use, see Crosby 2007.
sexual tension, arousal, and pleasure: Arnow 2002 and Holstege 2003.
and fellatio twice as often as women: Laumann 1999b.
becomes less and less sensitive : Payne 2007. Shafik 2007 found that stimulating the urethral opening keeps the nerves and muscles of the penis activated to maintain a throbbing, hard erection, thus enabling a forcefully ejected stream of semen, which has a better chance of impregnating the woman.
from pain during sexual intercourse: Payne 2007.neurochemical stars need to align : Murstein 1998 found that men score higher than women in studies of sexual interest, frequency of sexual arousal, and sexual enjoyment.
happens three minutes before entry : Meston 2004. For more on women's orgasm, foreplay, and vaginal-penile intercourse, see Weiss 2009. For more on female sexual function and dysfunction, see Basson 2005.
penis or clitoris to orgasm: Georgiadis 2009. Muehlenhard 2009 found that both men and women pretend or fake orgasm--females 67 percent and men 28 percent of the time during penile-vaginal intercourse.
periaqueductal gray (PAG)--activated intensely: Parra-Gamez 2009 and Georgiadis 2009 found that the only prominent gender difference during orgasm was greater male activation of the PAG--the area for decreased pain and sexual moaning. Holstege 2003 found that brain scans taken of men while they are ejaculating show vivid activations in the ventral tegmental area (VTA), where dopamine is made.
problems of his early twenties : Revicki 2008 found that up to 75 percent of men ejaculate within ten minutes of penetration. Richters 2006 found that men had an orgasm in 95 percent of sexual encounters and women in 69 percent. Weiss 2009 found that women's likelihood of orgasm during intercourse increases when penile-vaginal penetration lasts longer. For more on female sexual function, see Meston 2004, McKenna 2000, Mong 2003, and Basson 2005.
or off by the brain : Truitt 2002. Beaureguard 2009 found that the anterior cingulate cortex (ACC), the worrywart center, is alerted to the impending erection. This heads-up in the ACC lets it team up with other brain circuits, like the insula, or disgust center, to turn off the spinal erection generators when necessary.
seven to thirteen minutes or more : Waldinger 2005. Corty 2008 found that the normal, average length of intercourse is 3 to 13 minutes. Sex therapists recommend that men use Kegel squeezing exercises, masturbation, and mental distraction during intercourse, or condoms and penile-numbing gel if necessary, to treat rapid ejaculation. SSRI medication is also available to slow down ejaculation and help males last longer. However, SSRIs can prevent sexual arousal entirely.
experienced it at least once : Symonds 2007 and Revicki 2008. The diagnosis of PME, premature ejaculation, is made only when a lack of ejaculatory control interferes with sexual or emotional well-being in one or both partners. For more on the treatment of PME, see Sadeghi-Nejad 2008.
achieving an erection : Tanagho 2000 found that when the penis is massaged or when a sexual fantasy occurs in the brain, an erection is initiated parasympathetic division of the system. These PNS nerve branches cause the release of nitric oxide in the penis, dilating the arteries to fill it with blood and become hard. Viagra-like medicines act on the nitric oxide system to aid erections. Erection stops when the parasympathetic stimulation is discontinued and the SNS, the sympathetic division of the autonomic nervous by the PNS, the autonomic nervous system, starts constriction of the penile arteries, forcing blood out and making the penis get soft.
get the erection he wanted: Tanagho 2000. For more on erections, see Brody 2009 and Costa 2009.triggering the brain's sleep center : Veenema 2008 found oxytocin is released in the male brain, during and after sex, for up to four hours, thus increasing sedation and relaxation and decreasing anxiety. For more on oxytocin and sex, see Waldherr 2007.