At last, Gottman, partnering with two other researchers, has weighed in on the topic of why people have affairs.

Why affairs happen, according to Gottman

According to Gottman et. al., the development of an affair situation follows a predictable sequence, which they call the Gottman-Rusbult-Glass Cascade. They report that affairs begin when one partner begins feeling shut out of the other’s attention and care. One partner concludes that they can’t count on the other one, leading to feelings of distance and hurt and the thought that the shut-out partner would be better off elsewhere. RELATED: 5 Reasons Cheating On Your Spouse Is A Truly Terrible Idea

The seven steps in the Gottman-Rusbult-Glass Cascade — and why they make people vulnerable to affairs

1. Turning away.

In his previous research, Gottman found that constantly in marriage, partners make verbal and nonverbal requests for attention and support. He calls these “bids.” A “bid” would be, for example, when one person comes home and wants to discuss something that happened that day, or a request for help with housework, or a nonverbal move toward sex. Gottman discovered that one key ingredient of a happy marriage is that the partners turn toward one another’s bids and answer them positively, rather than turning away with a negative response. Examples of “turning away” might be when the spouse won’t look up from the TV while the bidding spouse describes a problem that happened at work that day, or when pleas for help with housework go ignored, or one partner turns over and goes to sleep when the other approaches them for sex. RELATED: 13 Simple Things That Can Trigger An Affair

2. The “Negative Absorbing State.”

In this phase, the bidding partner becomes used to being turned down and turned away from. They may hide their feelings in order to keep the peace, but they feel hurt, sad, angry, and resentful. These feelings grow worse and worse every time the person feels turned away from again. Furthermore, they bid for attention less and less as they anticipate being turned down more and more. RELATED: How To Recover From An Emotional Affair — And Keep Your Marriage Intact

3. The Problem of Comparison.

The bidding partner builds in his or her mind another, ideal partner based on how he or she wishes their spouse would answer their bids for attention. When you married (at least, we hope so), each partner thought the other was The One compared to anyone and everyone else. But now the turned-away partner no longer sees the turning-away spouse as better than anything else that might walk down the pike. And it’s a lot easier to stay committed to someone you see as better than any other option than it is to stay committed when you think anyone else would probably be a better option. RELATED: The Ironic Excuse People Use To Justify Their Affairs

4. The Erosion of Trust.

Now the partner no longer trusts the spouse to care about meeting their needs. The more negative the person feels, the more he or she minimizes the positives of the ignoring spouse and dwells on the negative qualities.

5. Trashing the Spouse.

Then the bidding spouse begins to talk negatively about the ignoring spouse all the time — to himself or herself, or, worse, to other people. RELATED: Who Your Spouse Is Most Likely To Have An Affair With — And Why

6. The “Denigrating Relationship.”

Now the cheating partner stops relying on the spouse to get their needs met. They believe they cannot rely on this spouse anymore. They’re idealizing the thought of a better relationship and denigrating the one they have in their mind. Instead of thinking good thoughts about the relationship, their thinking is against the relationship. “Maybe we would be better off apart.” Now, this is a “denigrating relationship,” where the person puts the relationship down in his or her head and seeks alternative ways to get needs for companionship and sex met. RELATED: 3 Infidelity Stories That Show How The Truth Can Hurt — But There’s Always A Silver Lining

7. The boundary is crossed.

Because this partner has written their spouse off as a way to get needs met and is looking to other people, a vulnerable moment will happen, and a third party will take notice. Then eventually a boundary will be crossed and that relationship will become an affair.

Two cases Dr. Gottman leaves out of his list

John Gottman is one of the most respected researchers out there and yet, this cascade, while proven, and while we know in our hearts it’s correct, still does not cover every case out there. So if you’re struggling to understand why your spouse cheated, it’s no wonder. Even the best experts don’t always get all the information in one place. RELATED: The Surprising Reason People Cheat (And Why It’s Happening Now More Than Ever Before)

The cheaters Gottman forgets:

1. The caregiving cheater, whose spouse is demented or otherwise disabled and can no longer function as a marriage partner. 2. The case in which the cheating partner has deep-seated personality problems and can feel no empathy for the spouse at all. This person self-aggrandizes with cheating, often having multiple affair partners at once or even a secret second spouse. The person, who may have a drug or a sex addiction, or may suffer from a narcissistic or borderline personality disorder, victimizes his relationship partners in a willful attempt to feel powerful by getting one-up on them. If you’ve discovered your spouse had an affair, you will see yourself in one of these three scenarios. Still, affairs are even more complicated than this, and only marriage counseling combined with soul-searching, reading, and a lot of hard work can untangle all the whys of your own heartbreaking situation. RELATED: You Can Find True Love After Divorce — But There’s Something You Need To Do First P. D. Reader edits and writes for the Medium publication Unfaithful: Perspectives on the Third Party Relationship and is the author of Struggling In or With An Affair? A Guidebook. This article was originally published at Medium.com. Reprinted with permission from the author.