Infidelity or extramarital affairs have been extensively studied over the past two decades.
Basically, when it comes to infidelity, two related explanations have been given.
The first explanation is probably the most well known: Spouses cheat because of problems in their relationship - something is missing, passion has faded, partners feel lonely, people find someone who treats them better or who appreciates them more than their current spouse, and so on.
Simply stated, people claim that they are not happy in their relationship so they look for love and affection elsewhere.
The second explanation is more detailed in nature.  This explanation ignores the reasons that people "give" for cheating and looks deeper into our human nature.
The second explanation explores what it means to be human and asks, "why is being faithful to a spouse so difficult for many people to do?"
Probably the best way to think about these two explanations is to view them as two sides of the same coin.
One explanation looks at what people "say" about infidelity, while the other explanation looks at "how and why infidelity" occurs.
Together, both explanations give us a more complete picture about infidelity, love and romance.






On the pages that follow, these specific issues are addressed:
• coming to grips with infidelity
• making the decision to cheat
• role of sexual desire
• who is likely to cheat
• how to prevent infidelity













Coming to Grips with Infidelity
Again, a lot of research has been done on the topic of human sexuality, especially infidelity.
Unfortunately, most of the evidence indicates being faithful to a single romantic partner over the course of one’s lifetime is difficult to do.
And while not everyone will stray, it is estimated that 30 to 60% of husbands and wives will cheat on a spouse at least once during the course of their marriage.
To understand and come to grips with infidelity, it helps to examine the following questions in detail:
• How do people make decisions about their sexual behavior?
• What is the role of "will power" or "self-control" when it comes to infidelity?
• What motivates our sex drive?
• What makes it so difficult for men and women to be faithful?
• Why do people cheat, but then expect or demand their partners to be faithful?
• Why are some men and women more likely to cheat than others?
• What can be done to prevent infidelity?





How Do People Make the Decision To Cheat?
To start with, human sexuality is incredibly complex.  Decisions about our sexual behavior are typically not planned in advance.  Few people intentionally plan on committing infidelity (at least not the first time it happens).
When making promises to be faithful, most people are serious and have every intention of keeping their word.
But while people generally have the best intentions when making such promises, human behavior is not always governed by the fact that vows were taken and that promises were made.
When it comes to making decisions about love and betrayal, logic and reason have a difficult time competing with our emotions for control.  So from time to time, our emotions influence our behavior and lead us down paths we had no intention of traveling.
In fact, three separate emotional systems are involved in cheating - sexual desire, romantic love, and attachment.  And often these distinct emotional systems pull people in different directions.
The movie, Unfaithful, does a great job of portraying how infidelity occurs.  In this movie, Diane Lane’s character plays a happy housewife, who cheats on her husband, because of a chance encounter with an attractive stranger.  Her emotions, in particular, her sexual desire, gets the best of her resulting in decisions which even she finds appalling.
In short, most infidelity occurs, not because it is planned, but because people find themselves in situations where their emotions overwhelm them.
What types of situations influence our emotions and bring out the worst in our behavior?
• Being close or interdependent on someone other than one’s spouse
• Being around someone who is sexually interested
• Spending a lot of time one-on-one with someone else
• Not feeling close or connected to one’s spouse (e.g., feeling lonely, being upset or angry with a spouse, etc.)
• Situations that create the sense of opportunity - the feeling that one will not get caught (e.g., meeting someone in private, out of town trips, etc.).
• Situations involving alcohol or drugs
When placed in these types of situations, one’s emotions often prompt people to act in ways which are contrary to what is right.  On occasion, poor decisions get made.  Unfortunately, for many people, it is very difficult to always be in control of one’s emotions when placed in these types of situations.
What about "will power" or "self-restraint?"
Research shows that "will power" or "self-restraint," alone, does little to change or influence our behavior.
In fact, some cultures have decided that individual "will power" and "self-restraint" can not be trusted.  Some cultures have made the decision that the best way to prevent infidelity is to make sure that the situations listed above do not occur - essentially, controlling situations is the best way to control behavior.
In western cultures, however, we place greater value on individual responsibility.  We do not collectively try to prevent these types of situations from occurring.  Rather we allow situations to happen, but then we hold individuals accountable for their behavior and we expect people to behave appropriately.
Individuals are supposed to exercise their self-restraint and have the will power to control their emotions and their actions.
Unfortunately, for many people this does not work.
Perhaps a somewhat related example will help bring home this point.
Relying on will power or self-restraint also fails to work when dieting.  The very same problem occurs - people make promises and vows they can not keep.  More often than not, will power and self-restraint are not enough to control one’s weight.  To diet successfully, more drastic measures are often needed.  Successful dieting often requires a change in lifestyle, environment, social networks, and sometimes even surgery.
Of course, there are some important differences between dieting and trying to be faithful to one’s spouse.  The consequences of cheating are much more severe than the consequences of failing a diet (most people admit to failing a diet, but not to cheating).  In any case, people do struggle with these issues and making promises alone typically does not result in a lasting change.
Overall, infidelity, like many other human behaviors, is difficult to control.  Being faithful to a spouse is more complicated than simply making promises to do so.
Being faithful to a spouse often requires avoiding situations which bring out the worst in our behavior...


Role of Sexual Desire
Part of the reason why infidelity is so common stems directly from our sexual desire.
Our desire for sex, whether we are conscious of it or not, is one of lives most basic and fundamental needs 
To begin with, we want to apologize for coming across as sexist.  But when talking about sexual desire, some sexism is involved.  There are some sex differences between men and women.
And for the most part, our sexual desire influences a lot of our behavior and we are not always aware of its influence.  
For example, why are most women so concerned about their appearance – looking young and beautiful – even putting on make-up to enhance their beauty?  In fact, it is estimated that people spend more money on trying to appear beautiful than we do on education.
And why are men so obsessed with status, respect, and success?  And why are they so concerned about their height?
People care so much about these issues because they are directly linked to our sexual behavior.


Why is sex so important?
Because whether we like to acknowledge it or not, our sexual desire underlies much of what we do.
The long story, told short:
For a more detailed discussion about how evolution shaped our human nature,.
Otherwise, here is an abbreviated version:
Evolution shaped human behavior – how we think, feel, and behave.  And most of the time we are not aware of the motivations that influence our behavior – life kept many of the factors that influence our behavior hidden from us (we don't really need to know why we do the things we do, just as long as we do them).
But, evolution rewards life forms that survive, reproduce and help relatives get ahead.  So evolution rewarded humans that were sexual in nature – we are all the descendants of individuals who were driven and motivated to act on their sexual impulses.  Accordingly, people today are stuck with the sexual desires which drove our ancestors to reproduce (and this process went on for millions and millions of years).
And whether we like it or not (again, evolution didn't care that we liked what we were doing, just as long as we did it), cheating is a part of our sexual desire.  For millions of years, people who cheated on their mates reproduced faster than more sexually reserved individuals (cheaters won at the game of creating offspring).  So now the desire to cheat is a universal part of our human nature - something we inherited a long time ago from our cheating ancestors.
This, however, does NOT mean that EVERYONE will cheat; it only means that the tendency to cheat is innate - it’s part of who we are.
So, why do some people act on their desire to cheat while others remain faithful...















Who Is Likely to Cheat
While the desire to cheat is a fundamental, and unconscious, part of our human nature, not everyone will be unfaithful.
Like most of our behaviors, infidelity is not intentional, but, for the most part, it is situational driven.
When placed in the right situation (or wrong situation, in this case), our emotions can get can prompt us to act in ways which are counter to our beliefs.  Please note that some of the factors listed below are drawn from Buss and Shackelford’s work on infidelity.
What factors influence an individual’s willingness to cheat?
Attractiveness

All things being equal, an individual’s attractiveness influences how likely he or she is to cheat.  Attraction comes in many different forms – it is influenced by one’s physical appearance, one’s social skills, and one’s tangible resources (money).  The more one is in demand, the more likely one is to cheat.  People, who have higher incomes, more education, and successful careers, are more likely to cheat than people who are less successful.  Physical attractiveness also plays an important role.
Opportunity
Again, all things being equal, the more individual free time people have the more likely they are to cheat.  Couples who have separate social lives, friends, careers, travel plans, and so on are much more likely to cheat than couples who spend most of their time together.  The more opportunity people have to cheat, the greater the odds that cheating will occur.
Risk Taking
People who like to take risks or have a sense of adventure are more likely to cheat than people who are more fearful or timid by nature.  There is most likely a genetic component involved in risk-taking behavior - some people may be predisposed to taking risks.
Personality Differences
Individual personality traits also play a role in who is likely to commit infidelity.  Individuals who have psychopathic and Machiavellian personality traits are much more likely to cheat.
Power
People in a position of power are more likely to cheat.  Power increases one’s confidence leading powerful individuals to act in more assertive and outgoing ways.  Powerful people are more likely to make direct eye contact, strike a confident pose, and approach potential lovers.  Power influences the likelihood of cheating for both men and women.
Who Is Likely to Cheat
Sexual Desire
Sexual desire varies from person to person.  Some people have a very high sex drive while other people are much less concerned or interested in sex.  People with a high, rather than low, sex drive are more likely to cheat.  Again, sexual desire appears to be influenced by genetic factors.  Some people are inherently more easily aroused and driven by their desire for sex than other people.  People who have multiple affairs are often addicted to the novelty and excitement which infidelity can provide.  Men, more so than women, also tend to have a higher sex drive and are more likely to cheat.
Attitude toward Love and Romance
Attachment and Love Styles
Some people view love and romance as a sacred bond between two individuals.  Other people see love as a game, where the goal is to manipulate another individual and gain emotional power over a partner.  People who view love as a game are much more likely to have multiple love interests; cheating is just another way to gain control over one’s spouse.  Also, people with a dismissing style of attachment, are more likely to cheat.
Relational Problems
As problems emerge in a relationship, people are more likely to cheat.  Infidelity is more common in relationships where people feel misunderstood, under appreciated and where fighting and bickering is common.
Sense of Entitlement
Some people, due to their position in society, their beliefs about gender roles, or their cultural upbringing, believe that it is their right to cheat on their partners.  In other words, some people believe that cheating is a privilege to which they are entitled.  Such individuals, philanders, often engage in infidelity with little guilt or remorse.
What Steps Can Be Taken to Prevent Infidelity?
For starters, many of the things which influence the likelihood that a spouse will cheat are difficult to control.
For instance, it can be difficult to limit how spouses spend their time outside of the relationship – social and work commitments often require spouses to spend a lot of time apart, providing an opportunity for cheating to occur.
And it can be even more difficult to control a partner’s level of attractiveness or a partner’s willingness to take risks – again, both factors that influence how likely a spouse is to cheat.
On the other hand, there are a lot of things that you can do to make your current relationship more satisfying.  And people who are happily married are less likely to cheat.
Why Men Cheat
To be honest, both men and women cheat.  But with that said, men are more likely than women to cheat and there are some differences between the sexes when it comes to cheating.
In order to understand why men cheat, it helps to understand what causes both men and women to be unfaithful.
Why do both men and women cheat?
The science of cheating is clear on this point: Roughly 3% of all mammals, including humans, practice what is called pair bonding or monogamous mating.  However, even within the 3% of mammals that practice monogamy, very few species, including humans, are truly monogamous.  In fact, when it comes to both men and women, monogamy is not our natural sexual strategy.
To make a long story short, for millions of years, the desire to mate with multiple partners was a useful reproductive strategy.  Men and women, who had multiple partners, likely produced more offspring than people who were faithful to a single mate.  Cheating was a strategy to increase reproductive success and diversify risk.  Or think about it this way: investing in a mutual fund (multiple stocks) is, on average, a better financial strategy than putting all of your resources into a single stock.
Because a multiple partner approach was a better reproductive strategy than monogamy, men and women living today are the descendants of people, who had the desire to have sex with more than one person over the course of their lifespan.  Simply put, we have inherited this trait from our ancestors – it is a part of our human nature.  This does not mean that everyone will cheat on a partner or that people are fully aware of their unconscious sexual desires.  For a more detailed discussion on the nature of cheating,.
How are men and women different when it comes to cheating?
While both men and women cheat, there are important sex differences when it comes to cheating.  The sex differences that influence cheating are based on two basic biological differences between men and women
First, men and women differ when it comes to eggs and sperm.  Men can produce hundreds of millions of sperm per day.  By comparison, women are born with a million or so eggs, but only a fraction, roughly one egg released every 28 days over a short period of time - from puberty to menopause - has the potential to create life.  Simply stated, women have about 400 viable eggs to use (and taking into account gestation, only about 20 actual opportunities to reproduce), while men are capable of fathering an unlimited number of children.
The second basic biological difference deals with gestation.  Embryos grow and develop in women, not men.  For men, reproduction can literally take just a few minutes of effort; while for women it involves, at the very least, a nine-month process.
From a biological point of view, men can constantly and quickly engage in reproduction while women are much more limited in their ability to do so.
These biological differences influenced our psychological desires before the invention of modern forms of birth control and still influence our unconscious sexual desires today.  Men are more likely than women to think about sex and fantasize about having sex with multiple partners.  In fact, a multi-billion dollar industry - pornography - exploits this basic sexual difference.
Given this basic biological difference, here are some key differences between men and women when it comes to cheating:
• Men are more likely than women to cheat with someone who is less attractive than their current partner.  Women cheat up while men are more opportunistic when it comes to cheating.
• Men are more likely than women to have a one-night stand.  Women are more prone to having emotional affairs.
• Men are less likely to consider leaving their partners after cheating.  When women cheat, it tends to be more emotionally involved so they are more likely to consider ending their current relationship.
• Men are more likely than women to repeatedly cheat on a spouse or partner 





Why Women Cheat
Both men and women cheat for a variety of reasons – due to problems in their relationship, due to their need for intimacy, or because they have a high sex drive – just to name a few.
But, when focusing on sex differences alone - differences based on biology - men and women cheat in different ways.  Men are more likely to cheat opportunistically.  That is, more often and with someone who may be less attractive or desirable than their current partner?
Women, by comparison, tend to cheat more selectively.  Women tend to be more flirtatious, risk-taking, and act in sexually provocative ways when they are ovulating.  Women are also attracted to more masculine and physically attractive men when ovulating.
The explanation for this behavior is called the sexy son hypothesis.  The argument goes like this: because women are more limited in their ability to reproduce, women who acted in ways that increased their reproductive success - like mating with the best men available when ovulating – were more likely to have healthy and attractive children.  Possessing this trait or tendency would have led to a reproductive advantage, which would have become widespread over the course of human evolution.
In short, men and women are different.  Women are more likely to cheat up while men are more likely to cheat around.
But it also helps to keep in mind, that while there may be sex differences when it comes to cheating – men and women are more alike than they are different.  Both sexes cheat for a variety of reasons.