1. A few dozen
   1,000
2. 150 million

Although the average ejaculate contains about 150 million sperm, only a few dozen will complete the arduous journey all the way to the egg.

1. 15 percent
   25 percent
2. 45 percent

Between 10 and 15 percent of adult women report anorgasmia, or never having an orgasm.

1. inability to have an orgasm
   infidelity
2. bisexuality

A 2008 headline-sparking genetic investigation out of Sweden identified allele 334, a genetic variation associated with male infidelity. Allele 334 interferes with the brain’s processing of vasopressin, a neurochemical associated with monogamous pair bonding.

1. 30 percent
   50 percent
2. 70 percent

A 2011 survey from Indiana University’s Center for Sexual Health Promotion found that 70 percent of men welcome sex toy assistance in the bedroom.

1. oxytocin
   dopamine
2. testosterone

Locking lips with a fellow is like taking a testosterone pill, since guys pass it along in their spit.

1. dopamine
   serotonin
2. oxytocin

During the early attachment phase of love, serotonin takes a back seat, residing at low levels, while other reward-regulating chemicals take over. As a result of that serotonin dampening, people become borderline obsessed with their beloveds, unable to focus or eat whenever apart.

1. 500
   2,000
2. 8,000

The clitoris is an incredibly sensitive sex organ, and its external hooded glans is packed with 8,000 nerve endings.

1. estrogen
   oxytocin
2. vasopressin

Oxytocin is especially potent in the female body, washing over the brain during a climax as well as after childbirth, bonding mother and baby.

1. 3 percent
   10 percent
2. 30 percent

Only 3 to 5 percent of mammalian species practice lifelong social monogamy, sticking to the same pair bond for the life term.

1. women
   men
2. Neither. Men and women initiate "I love you" equally.

A 2011 study conducted at Pennsylvania State University found that male college students were more likely to fall in love and drop the magic three words sooner than their female co-eds.

1. true
2. false

Approximately two-thirds of adulterous men didn't think they would ever cheat on their partners. Women, on the other hand, tend to anticipate their cheating behavior before it happens.

1. flushed cheeks
   sweating palms
2. constricted pupils

People's pupils dilate rather than constrict when they're looking at someone who rings their bell. Moreover, heterosexual men find women with wider pupils more feminine and attractive.

1. 4
   8
2. 12

The female study sample reported 12 dates as the appropriate amount of time to wait before having sex, compared to men who preferred to sleep over after eight dates.

1. 1.5 percent
   5 percent
2. 11 percent

Based on 1994 survey data from British households, about 1.5 percent of people have never felt sexual attraction to men or women.

1. true
2. false

Most men apparently have better things to do than think about sex every 7 seconds. For instance, a study published in 1990 in the Archives of Sexual Behavior asked 49 male college students to tally up their sexual fantasies over a week, and the results averaged to just 7.5 sexy thoughts per day, which works out to once every 3.2 hours.

1. dopamine
   norepinephrine
2. adrenaline

During early-stage romantic love -- scientific terminology for the honeymoon phase -- the brain releases norepinephrine whenever we’re around a love interest, amping our heart rate and shaking us into action.

1. true
2. false

A recent Australian study at last debunked the popular correlation between sperm quality and vocal tone.

1. a drop in vocal pitch
   wearing less makeup
2. infidelity

Women's peak fertility can result in a range of interesting behaviors, including shopping for new outfits and wearing more makeup. One study also found that ovulating women are more likely to cheat on their current partners.

1. sight
   smell
2. taste

Of course, heterosexual women want handsome hunks by their sides, but the nose might know better than the eyes. Research has found that the female body innately "sniffs" out a man's genetic compatibility, and those with the most pleasing musk are better candidates for having healthier offspring.

1. dopamine
   oxytocin
2. vasopressin

Although oxytocin and vasopressin initially establish the romantic bond between two people, dopamine is what refreshes the romance as the years wear on. Brain scan studies of happily married couples have demonstrated how their dopamine reward system lights up in response to merely seeing a picture of their 'til-death beloved.