The Dangerous Passion: Why Jealousy Is as Necessary as Love and Sex (23 page)

Notice the emotional intimacy, private whispers, personal
attention, and psychological closeness with someone Jayne already knew. None of
these ingredients pervade the typical man’s sexual fantasies, which more often
center on raw sex with strangers. Fifty-nine percent of American women but only
28 percent of American men report that their sexual fantasies typically focus
on someone with whom they are already romantically and sexually involved. Not
all women’s fantasies, of course, center on men they already know.

Here is one from Bobbi, a married woman in her 30s, about a man
she had never met: “I’m with a man I’ve never met in real life. He’s a cowboy
and an animal lover, self-confident and strong, yet also tender. We spend the
whole day together and discover that we have many common interests. He . . .
[is] hanging on my every word, and looks at me with burning desire. At his
home, we eat, drink, listen to music, dance close. . . . He says that I’m the
only one who has ever made him feel this way. This excites me and makes me want
him, too. His first kisses are gentle, and I return them that way. Then he
kisses me more aggressively, and I return that energy. When we undress each other,
I notice his lean, taut stomach, his contoured legs, his dark chest hair. As he
caresses me, he makes me feel worshiped, adored, safe, and very sexy. He takes
me to the edge with breast stimulation and oral sex, then thrusts inside me. We
climax together, then cuddle in bed for the rest of the day, talking and
touching.”

Emotions and personality are crucial for women. Although Bobbi’s
fantasy centered not on her husband but on a man she had never met, they don’t
just jump into bed. They build up to sex by getting to know each other, sharing
common interests, dancing, and eating. Bobbi becomes the center of the man’s
desires, arousing him like no other woman before her. He worships her, makes
her feel safe and protected, all qualities that signal emotional involvement
and commitment over time.

The formal studies bear out these themes: 57 percent of women
but only 19 percent of men report that they focus on feelings as opposed to
visual images. As one woman observed, “I usually think about the guy I am with.
Sometimes I realize that the feelings will overwhelm me, envelop me, sweep me
away.” Women emphasize tenderness, romance, and personal involvement in their
sexual fantasies, paying more attention to the way their partner responds to
them.

Men’s fantasies, in contrast, focus on sexual variety, since
those men in the past who were inclined in this direction tended to reproduce
more than men not so inclined. It’s not that men lack the desire to marry, as
as the journalist Natalie Angier and other critics have mischaracterized the
theory. It’s that men are more likely than women to be on the lookout for the
occasional casual fling in addition to whatever long-term commitments they
make.

It surprises me that some ideologues insist that the sexes are
identical and that women lack discernment when it comes to casual sex, just
like men. The data don’t support these positions. Women’s reproductive
resources are precious and finite, and ancestral women did not squander them on
just any random man. Obviously, women don’t consciously think that sperm are
cheap and eggs are expensive. But women in the past who failed to exercise
acumen before consenting to sex were left in the evolutionary dust; our
ancestral mothers used emotional wisdom to screen out losers. Lust is one
thing; acting on it is another. Not all people who experience extramarital
desires give in to them.

What telltale signs reveal a cheating partner? Some of these
signals are obvious—an unexplained absence, a sudden decrease in sexual
interest, unfamiliar sexual scents on a partner, an open flirtation with
others, or catching the partner in a nude embrace with a neighbor. Many signals
are more subtle, such as the personality characteristics of a partner. This
section explores who is susceptible to infidelity and what clues they leave
behind.

When studying the avian species of zebra finches,
Poephia
guttata,
the evolutionary biologist Nancy Burley made a striking
discovery. These birds were presumed to be monogamous, preferring to mate with
a single partner for many breeding seasons. When she monitored the birds over
the course of several months, however, she observed that some males in fact
copulated with several females, others copulated with only a single female, and
still others remained celibate. She also observed that the zebra finches varied
in coloration, and that some colors were more attractive than others.

Burley performed an unusual experiment that probably would be
unethical to perform on humans. She created bands of different colors and
placed them on the legs of the birds. Some males were banded with red colors,
which her observations suggested were highly attractive to females. Other males
were banded with green, a color less attractive to females. For females, black
bands seemed to be the most attractive to males, so some were banded with
black. Others remained unbanded. In this manner, Burley varied the relative
attractiveness of the zebra finches, and then observed their mating behavior
over the following 22 months. Food was readily abundant in her laboratory
aviary, so it did not play a role in mating.

She discovered two intriguing results when birds paired up with
those who were less or more attractive than themselves. First, the birds lower
in attractiveness devoted more effort than the birds higher in attractiveness
to the care and parenting of their offspring chicks. It was as if the less
desirable birds had “recognized” that they had to compensate for their lower
attractiveness with increased parental care; the birds higher in mate value
were able to trade their attractiveness for a lighter workload. Second, the
male zebra finches who were more attractive than their partners more often
mated with other female birds, enjoying extrapair liaisons in addition to sex
with regular mates. The birds higher in mate value, in essence, traded their
relatively greater attractiveness for increased opportunities for infidelity.

Do humans show a similar pattern? The first evidence for the
importance of attractiveness differences for marital infidelity came from a
Psychology
Today
survey. This study asked each participant: “Describe your partner’s
desirability: Much more desirable than I; Slightly more desirable than I; As
desirable as I; Slightly less desirable than I; Much less desirable than I.”
Those higher in mate value were defined as those who described their partners
as “slightly less” or “much less” desirable than themselves. Those lower in
mate value were defined as those who described their partners as “slightly
more” or “much more” desirable than themselves.

The study also asked the participants how willing they were to
engage in an extramarital sexual relationship. It posed two questions: How soon
after you began living with your partner did you first have sex with someone
else (if you have had sex with someone else at all)? With how many people have
you had extramarital affairs over the course of your relationship? Fifty-eight
percent of the partners turned out to be well matched, showing comparable
levels of mate value. What about those who were mismatched, where one partner
was more desirable than the other? The partner higher in desirability turned
out to be more likely to have more extramarital affairs with more partners than
those who were lower in desirability. Furthermore, the more desirable partner
in each pair was more likely to have affairs
earlier
in the marriage.
They began having affairs 6 to 8 years after the wedding. In contrast, those
who were equivalent or lower in desirability waited 12 to 15 years before
starting an affair, if they had an affair at all. Like zebra finches, human
affairs seem to be affected by the relative mate value of the partners.

In a more recent study of newlywed couples, Todd Shackelford and
I explored the importance of attractiveness differences for susceptibility to
infidelity in more detail. We studied 107 couples using three sources of data:
self-reports, partner reports, and interviews with each couple. When the
couples were physically separated to preserve privacy, we asked each spouse to
estimate the likelihood that their partner would perform various acts of
infidelity over the course of the next year. These included flirting with a
member of the opposite sex, passionately kissing, going out on a romantic date,
having a one-night stand, having a brief affair, and having a serious affair.
Subsequently, they all estimated their own likelihood of engaging in each of
these types of infidelity over the course of the next year. Participants were
then asked two questions: If this event occurred, what is the probability that
you
would end the relationship? If this event occurred, what is the probability
that
your partner
would end the relationship?

Following these private estimates, each couple was interviewed
together by a pair of trained interviewers, one man and one woman, drawn from a
rotating team of eight interviewers. Immediately after the interview, the staff
members independently judged them on their “overall attractiveness as a
potential mate,” which we defined as “market value to opposite sex.” The
separate judgments of each interviewer were then combined to form an overall
measure of everyone’s mate value. To evaluate dissimilarity, we then calculated
the disparity between the married partners in their overall attractiveness as a
potential mate.

We discovered that the partner higher in mate value was
significantly more likely to commit infidelity, confirming the results of the
Psychology
Today
study. Women married to more desirable men, for example, judged it
more likely that their husbands would kiss, date, have a one-night stand, and
have a brief affair with someone else. Furthermore, we discovered that
dissimilarity was linked with the likelihood of ending the marriage if their
partner had an affair, but this was only true for the more serious types of
infidelity. If the less desirable partner flirted or kissed someone else, this
could be overlooked, or at least would not result in divorce. If the less
desirable partner had a one-night stand, brief affair, or a serious affair,
however, the more desirable partner would seek a divorce. The less desirable
partners, in contrast, would tolerate infidelity by their more desirable
partner and stated that they would not seek divorce.

These findings have some degree of cross-cultural generality, as
illustrated by a study by Bram Buunk and his colleagues of 82 Dutch men and 132
Dutch women, all married, with an average age of 41. They examined the effects
of relative mate value on a person’s desire for extramarital sex and on their
actual frequency of extramarital sex. Desire was assessed through this
question: “How many times did you want to have sex with another (wo)man during
your marriage or cohabitation?” They were also asked how many extramarital
partners they had had.

The effects of relative mate value also proved especially strong
for the Dutch women. Women who perceived themselves as higher in mate value
than their partners were more likely to express a desire for extramarital sex
and were more likely to act on those desires. Women who felt that they were
well-matched with their partners, equals in what they brought to the mating
table, were the least likely to desire or engage in affairs. All these studies
point to a singular conclusion: those who are higher in mate value are
especially prone to infidelity.

Time and effort in each person’s life are finite. Life can be
viewed as a series of decisions about how to spend one’s time. Time spent at
one activity necessarily precludes time for others. Some of the most important
decisions men and women face are how much effort to spend pursuing various life
tasks, such as finding a mate, getting ahead in the workplace, and raising a
family. Effort devoted to getting ahead takes time away from the family. With
each activity, however, we reach a state of diminishing returns, where
additional effort yields less and less payoff.

Consider a simple example—time spent securing food, either
through hunting or gathering. Clearly, the first few morsels of food are highly
valuable. They may make the difference between starving and surviving.
Subsequent portions of food the same day, however, are progressively less
valuable. In the extreme case, the hundredth hunk of meat has almost no value;
it’s left to rot uneaten. This logic suggests that time spent searching for
food is effort that shows diminishing returns. Natural selection should have
created decision rules for spending a certain amount of effort toward getting
food, but then ceasing this activity when the returns dip too low.

The same logic applies to the time and energy we allot toward
attracting partners, what evolutionary biologists call “mating effort.” Time
and energy spent in enhancing one’s appearance, trying to attract potential
mates, and pursuing extramarital affairs may be profitable up to a point,
reproductively speaking, but as a general rule, each individual will reach
diminishing returns. Additional effort spent enhancing one’s appearance may
make only a trivial difference, for example, and so it’s not worth the time or
added expense. The same logic applies to effort devoted to attracting mates and
securing affair partners.

But here is the catch: the rate of diminishing returns depends
heavily on the mating success of the individual. According to the theory of
diminishing returns, the mating payoff for highly attractive men should be far
higher than the payoff for less attractive men. Attractive actors such as Matt
Damon or Ben Affleck would achieve more sexual success per unit of mating
effort than less attractive actors such as Steve Buscemi or William Macy. A
man’s attractiveness to women, therefore, should influence his decisions about
how much effort to spend on mating.