The question is not "What kind of person is likely to have an affair?" but rather "What kind of relationship is likely to have one?" Affairs are far more common than most people realize and they happen for a wide variety of reasons. In over two decades of working with couples I've seen practically every kind of person and every kind of personality succumb to an affair, many of which I would never have anticipated would do so. What opened the door to the affair in the majority of these situations is not the character of the people involved but two other factors: Circumstance and Opportunity. The Circumstance: Our relationships are not static entities. Rather, the quality and strength of our bonds wax and wane naturally in response to the events, demands and circumstances of our lives. Anyone in a long-term partnership has gone through times in which they've felt angry and distant from their partners as well as times in which they've felt incredibly close and loving. When couples are in period of greater emotional distance, when their couplehood is at 'low tide', their relationship becomes vulnerable to an affair. The Opportunity: When a relationship is going through a rough patch and is vulnerable to an affair, it is like a pile of kindling that is ready to ignite. All it takes to set the flame is the right opportunity. This is why the vast majority of affairs happen at work, because most affairs are opportunistic, not premeditated. Workplaces simply provide ample opportunities to meet and interact with potential partners. When the circumstances in the relationship are just right and an opportunity presents itself, the affair ignites. The warning sign that often points to an affair The one sign that characterizes the vast majority of affairs is that the person having the affair has become emotionally disengaged from the relationship to one extent or another. We simply do not have enough emotional resources to invest in an affair without having to withdraw our emotional investment in our home lives. At times the person having an affair can seem completely detached or checked-out but such obvious signs are not common. More typically, the feeling one person gets is that their partner seems physically present but emotionally absent. Things might seem normal on the surface but it feels as though the other person is merely going through the motions. In other words, it feels as though the other person has become emotionally disengaged. To be clear, we all have days in which we feel slightly checked-out or preoccupied with other things. But when the drop in engagement persists over time it is reflected in various aspects of the relationship; changes in habits or small couplehood gestures that fall by the wayside, fewer efforts to initiate intimacy, less planning of mutual activities, less discussion of the future and other such indicators. People often realize their partner has become disengaged only in hindsight, once the affair has been discovered. It is then they look back and realize something has been amiss for a while, that they had felt the lack of engagement on some kind of gut level but had made excuses for it by telling themselves their partner was preoccupied with work or worried about the finances. Paradoxically, when couples go through a period in which they are angry at one another, the risk of an affair is not as high (although it does exist) because anger is actually a form of emotional engagement, albeit not a very pleasant one. Affair Prevention The best way to prevent an affair is for both members of the couple to monitor their couplehood and be aware when their relationship has entered a period of vulnerability. Rather than blame one another at such times (which will only create more distance) they should discuss the state of their union and do three things: 1. Acknowledge to one another they are going through a period of greater distance, one that is normal in relationships but one that needs handling nonetheless. 2. Take steps to communicate more regularly about their couplehood and assess what might be causing the distance at this time. 3. Decide on steps they can take to reconnect, such as taking time away as a couple, instituting date nights, reengaging in shared interests, or if necessary considering couple counseling. You can read about how to voice concerns to your partner without starting an argument here.