A CoupleStrong Blog

Affairs don’t always start with broken marriages or dramatic betrayals. In fact, one of the most important contributions from the late Dr. Shirley Glass — one of the world’s leading experts on infidelity — is her finding that many affairs begin not in the bedroom, but in seemingly innocent conversations. Her research reframes how we think about the causes of affairs and what makes relationships vulnerable.

From “Not Just Friends” to Something More

Glass’s work revealed that most affairs begin as friendships. Two people connect through work, shared interests, or mutual friends, and over time, emotional intimacy develops. This isn’t usually planned. In fact, many people who become involved in affairs still love their spouses and believe they are committed to their marriages. The danger lies in what Glass calls crossing the line from a professional or platonic relationship into a secret emotional connection.

Walls and Windows

One of Glass’s most memorable metaphors is the concept of walls and windows. In healthy relationships, partners build strong walls that protect the marriage from outside romantic threats, and large windows that allow openness and vulnerability between each other. Affairs often occur when these boundaries reverse — the wall is placed between the spouses, and the window opens toward someone outside the marriage.

This shift can happen subtly. A spouse may start sharing more personal thoughts, frustrations, or dreams with a coworker than with their partner. Over time, emotional intimacy with the “friend” deepens, and the marriage becomes increasingly closed off.

Risk Factors Shirley Glass Identified

Glass’s research highlighted several factors that make affairs more likely:

• Opportunity – Frequent contact with potential partners, especially in work or social settings without boundaries.
• Emotional Vulnerability – Feeling unappreciated, misunderstood, or disconnected at home.
• Poor Boundaries – Sharing intimate details about your relationship with someone outside of it.
• Rationalization – Convincing yourself that the connection is “just friendship” even as the intimacy deepens.

Importantly, Glass found that many people in affairs were not actively looking to cheat. The affair evolved gradually as emotional needs were met outside the marriage.

Prevention: Protecting the Window and the Wall

Preventing affairs isn’t about suspicion or control; it’s about conscious, proactive connection. Glass advises couples to keep their emotional “window” open toward each other — by sharing feelings, dreams, struggles, and triumphs with your partner first. At the same time, it’s crucial to keep “walls” in place with others by setting boundaries on emotional intimacy with people outside the marriage.

Checking in regularly with each other about your emotional closeness is key. So is noticing when you’re more eager to share news or vent frustrations with someone else instead of your spouse. That’s often the first signal that a wall is going up where a window should be.

The CoupleStrong Perspective

Shirley Glass’s research reminds us that most affairs are less about sexual dissatisfaction and more about misplaced intimacy. They happen when partners slowly drift apart and begin meeting emotional needs elsewhere. At CoupleStrong, we believe the antidote is intentional connection — nurturing trust, sharing openly, and protecting the emotional space between you and your partner.

Your challenge this week: Talk with your partner about your “walls and windows.” Ask each other: What can we do to keep our window open toward each other? Are there any walls we need to strengthen toward others? Those conversations are the first step toward safeguarding your relationship from the slow drift that can lead to betrayal.