A PhD student in psychology at the University of Montreal believes she has proven that a certain personality type is prone to infidelity. A husband with “avoidant attachment” style, she found, is likely to have multiple sexual partners and to cheat as a way of distancing himself from any relationship. And adultery is the No. 1 reason behind divorce.

Her work expands on the theory that a person who seeks attachment feels
• Secure that the relationship gives him or her a base
• That the relationship provides a safe haven
• That it is important to maintain proximity
• That separation leads to distress

Someone with an avoidant attachment style, on the other hand, is uncomfortable with intimacy. He or she probably did not have a close relationship with parents. As adults he or she may be unwilling to share thoughts and feelings. And he or she invests little emotion in social or romantic relationships. Incidentally, there appear to be just as many women as men with avoidant attachment style.

In her four studies, Geneviève Beaulieu-Pelletier, looked first at 145 young adults and than at another 270 adults, finding in both cases that those who avoided attachment were much more likely to cheat or think about cheating. When she followed up with two more studies to ask the cheaters their motivations, she found the No. 1 reason was the will to distance themselves from commitment and from their partner.

In other words, it’s not that the partner’s behavior drove them to cheat; it’s that their own makeup makes them push away from being in a couple.

“The act of cheating helps them avoid commitment phobia, distances them from their partner, and helps them keep their space and freedom,” she said.

The tough realization for a woman facing divorce is that, whether it was your partner or you who cheated, if it was because of avoidant attachment personality, it may be very difficult to change.

A man might remarry, but keep on cheating. A woman might avoid getting into another committed relationship and become a serial dater, or buy a dog.

But realizing one’s style of attachment is a first step.