Why People Cheat in Relationships: The Psychology Behind Affairs
Photo by Min An
People who have been cheated on often describe the same moment: the initial shock has started to settle, and the question that moves in to replace it isn't logistical. It's the deeper one. Not what happened, but why.
That question deserves an honest answer. The difficulty is that there is rarely a single explanation. Affairs usually emerge from a combination of psychological, relational, and situational factors that develop over time. For people across Alberta working through the aftermath of a partner's affair, understanding the actual psychology behind infidelity won't undo the harm. But it can make something incomprehensible slightly less so.
This article covers the full range of reasons people cheat, including the ones that are harder to talk about than simple unhappiness.
Table of Contents
- What Research Tells Us About Why People Have Affairs
- How Infidelity is Typically Defined in Relationships
- How Affairs Often Start
- Relationship Dynamics That Can Increase Vulnerability to Affairs
- Why Do People Cheat in Happy Relationships?
- Why Infidelity Can Occur Even in Loving Relationships
- Attachment Patterns and the Psychology of Infidelity
- Situational Factors That Can Increase the Likelihood of Affairs
- When Personal Patterns Play a Role in Infidelity
- When Unresolved Hurt or Resentment Leads to Infidelity
- Life Event Triggers: When External Circumstances Create Vulnerability
- The Psychology of Self-Justification in Affairs
- Frequently Asked Questions About Why People Cheat
- Final Thoughts
What Research Tells Us About Why People Have Affairs
Affairs rarely have a single cause. A study by Weiser and colleagues, published in the Journal of Sex Research in 2017, identified eight distinct motivational categories behind infidelity: anger, low self-esteem, lack of love, low commitment, need for variety, neglect, sexual desire, and situational factors. In the majority of cases studied, more than one category was present simultaneously.
That finding reframes the question most betrayed partners are asking. Instead of "why did they cheat," the more accurate question is usually which combination of factors was present, and how did they interact? That is a harder question, but it produces more useful answers.
Why There is Rarely One Simple Explanation for Infidelity
In clinical practice, affairs that appear to have a single obvious cause almost always have contributing factors underneath. The relationship looked fine from the outside, or the person who cheated describes themselves as happy, or there was no obvious crisis point. Understanding infidelity means holding several explanations at once rather than settling for the most convenient one.
How Infidelity is Typically Defined in Relationships
Infidelity extends well beyond a secret sexual encounter. Clinically, what matters is whether a relational agreement was broken and whether secrecy was involved. That threshold includes emotional affairs, sustained hidden contact, online or digital infidelity, and other behaviours a partner deliberately concealed. If you're trying to work out whether what happened in your relationship meets that threshold, our article on betrayal trauma covers the full breakdown of what counts as cheating and why the secrecy matters as much as the act itself.
How Affairs Often Start
One of the questions betrayed partners ask most often isn't just why the affair happened. It's when it crossed the line. Understanding how affairs typically develop is part of what makes the incomprehensible slightly more legible.
Affairs Rarely Begin With a Single Decision
Most affairs don't start with a conscious choice to betray a partner. They start as something that doesn't yet look like an affair: a friendship, a work relationship, a connection that feels uncomplicated and easy. The transition from that to infidelity tends to be gradual, and the gradual nature of it is part of what makes it possible.
How Emotional Affairs Develop Through Progressive Intimacy
Shirley Glass, whose clinical research on infidelity is among the most widely cited in this area, described how affairs typically develop through a process of progressive self-disclosure and emotional redirection. Conversations become more personal. Contact becomes more frequent. The other person begins to occupy mental space that previously belonged to the primary relationship. At each stage, the person can tell themselves nothing has happened yet, because technically nothing has. That internal permission structure is what allows the progression to continue.
How Secrecy Accelerates the Emotional Shift
Secrecy plays a specific role in this process. Once someone begins concealing the relationship from their partner, a psychological shift occurs. The concealment itself creates a sense of separateness from the primary relationship, and the forbidden quality of the connection can amplify its emotional intensity beyond what it would sustain if it were permitted. In clinical terms, some affairs feel more significant than they actually are, partly because the prohibition inflates them.
When a Friendship Crosses Into an Emotional Affair
The threshold is crossed not at the point of physical contact but earlier: when the person begins redirecting emotional energy that belongs in the primary relationship toward someone else, when they start comparing their partner unfavourably to the other person, and when they begin actively concealing the nature or extent of the contact. By the time most people consciously acknowledge that something has crossed a line, the emotional affair is already well established.
For betrayed partners trying to understand the timeline, this pattern is important. The affair rarely began the day they found out. It began much earlier, in a series of small decisions that individually seemed inconsequential.
Relationship Dynamics That Can Increase Vulnerability to Affairs
Relationship dissatisfaction is the most commonly cited reason people give for affairs, and it does appear reliably in the research. But the clinical picture is more specific than simply being unhappy.
Emotional Disconnection in Long-Term Relationships
What tends to precede an affair in this category isn't a dramatic rupture. It's a slow accumulation of small disconnections that neither person names. Conversations that stay on the surface. Physical intimacy that becomes infrequent without anyone acknowledging it. A sense of being more like functional co-inhabitants than partners. Conflict that gets avoided rather than resolved, so the same friction keeps returning without ever being addressed.
When Dissatisfaction Goes Unspoken
Clients who have had affairs often describe knowing, for a long time, that something was wrong, and never saying so directly. Not to their partner, and sometimes not fully to themselves. The affair became a response to that gap, but it was also a choice made without ever testing whether the relationship could close it.
That distinction matters considerably to the betrayed partner trying to understand whether they missed something or failed somehow. In many cases, the dissatisfaction was real and the communication about it was absent, and those are two separate problems with two separate owners.
Why Do People Cheat in Happy Relationships?
This is the category most explanatory articles either skip or handle poorly, possibly because it is more uncomfortable than relationship dissatisfaction as an explanation.
A meaningful proportion of people who have affairs report that their relationship was, by most honest measures, good. They described genuine love for their partner. They were not planning to leave. The affair did not happen because the relationship was failing.
Identity Changes and the Search for a Former Self
What clinical work with this population consistently reveals is that the affair was less about the relationship and more about something happening inside the person who cheated. A search for confirmation that they are still desirable. An attempt to recapture a version of themselves that existed before the weight of adult life accumulated, before the mortgage, the children, and the professional identity calcified into something that felt fixed.
Midlife Affairs and the Psychology of Unlived Possibilities
A midlife confrontation with unlived possibilities is one of the more common triggers in this category, and it has nothing to do with a partner's adequacy. The person is not leaving toward something better. They are reaching toward something they feel they have lost in themselves.
High Sensation-Seeking as a Factor
Some people have a genuinely high need for novelty and sensation that a long-term relationship, by its nature, cannot indefinitely satisfy. That is not a character flaw in isolation. It becomes one when the response to it is deception rather than honest conversation.
For the betrayed partner, this category is particularly disorienting because the usual explanation doesn't hold. Understanding it doesn't make it more acceptable. It does make it more legible.
Why Infidelity Can Occur Even in Loving Relationships
Yes, people cheat on partners they genuinely love. That is a direct clinical answer to one of the most searched questions connected to infidelity, and it deserves a direct response rather than a qualified one.
Love and Fidelity Are Not the Same System
Love and fidelity operate through different psychological systems. Someone can have a genuine, sustained attachment to their partner and still make choices that contradict that attachment. The presence of love does not explain the affair, and it does not excuse it. What it does mean is that the affair is not automatically evidence that the love was absent, or that the history of the relationship was false.
For betrayed partners, this is both harder and easier than the alternative. Harder, because it removes the explanatory simplicity of "they obviously didn't love me." Easier, because it means the relationship that existed before the affair was real, even if deception was running alongside it.
Attachment Patterns and the Psychology of Infidelity
Attachment theory provides one of the more clinically useful lenses for understanding infidelity, both in terms of who is more vulnerable to it and why the affair takes the shape it does.
Avoidant Attachment and Emotional Distance
People with avoidant attachment manage intimacy by maintaining emotional distance. Close relationships trigger discomfort rather than security, and the habitual response is to create space. An affair, particularly an emotional one, can provide a kind of intimacy that feels safer precisely because it exists outside the primary relationship, with less history, less expectation, and less exposure.
Anxious Attachment and the Need for Validation
Anxiously attached individuals have a hyperactivated need for reassurance that the relationship is secure. When that reassurance feels unavailable in the primary relationship, some people seek it externally. Affairs in this pattern often serve a self-worth function: the person is looking for evidence that they are wanted, chosen, and enough.
Disorganised Attachment and Fear of Intimacy
Disorganised attachment, which typically develops in early caregiving environments that were themselves frightening or inconsistent, produces a specific ambivalence: the person wants closeness and experiences it as threatening simultaneously. Infidelity in this pattern can reflect an unconscious pull toward destabilising what has become stable, because stability itself triggers anxiety in a nervous system calibrated for unpredictability.
Fear of genuine intimacy operates similarly. Some people pursue affairs not because the primary relationship lacks intimacy, but because its intimacy has become uncomfortably real, and the affair provides an escape hatch.
Situational Factors That Can Increase the Likelihood of Affairs
The situational dimension of infidelity is consistently underestimated in popular accounts, and it is worth being direct about what the research shows.
Work, Travel, and Environmental Opportunity
Repeated unsupervised access to someone with mutual attraction significantly increases the likelihood of an affair occurring, even in the absence of serious relationship dissatisfaction. Work environments with high emotional intensity, extended travel that creates physical separation from a partner, and close friendships where boundaries erode gradually: these contexts create conditions where the pull toward an affair can exceed the individual's stated intention to avoid one.
Alcohol, Substance Use, and Lowered Inhibition
Alcohol and substance use lower the inhibitory capacity that would otherwise interrupt the progression from attraction to action. This doesn't produce an affair on its own, but in a context where the other conditions are already present, it can remove the final barrier.
Why Opportunity Does Not Remove Responsibility
None of this eliminates individual responsibility. What it does is complicate the idea that character alone is a reliable predictor of fidelity. Context contributes, and accounting for it produces a more accurate picture than character explanations alone.
When Personal Patterns Play a Role in Infidelity
In some situations, the pattern of infidelity reflects enduring personal traits rather than relationship or situational factors.
Entitlement and Chronic Dishonesty
A pattern of entitlement, the belief that one's own needs and desires supersede relational agreements, appears consistently in people with repeated infidelity across multiple relationships. So does chronic dishonesty as a broader pattern: people who deceive in other domains of life don't typically become selectively honest in their intimate relationships.
Empathy Deficits and Discomfort Avoidance
Lack of genuine empathy for a partner's experience allows a person to continue an affair while observing the impact on someone they claim to love. Unwillingness to tolerate discomfort within the relationship, to have the difficult conversation, to sit with unmet needs long enough to address them honestly, is a pattern that makes affairs more likely when an easier alternative presents itself.
These explanations carry a different clinical implication: they suggest that no amount of relationship improvement would have prevented the affair, because the root issue was not the relationship.
When Unresolved Hurt or Resentment Leads to Infidelity
Sometimes infidelity emerges not from attraction or dissatisfaction but from unresolved resentment within the relationship. When someone feels deeply hurt, chronically dismissed, or rejected without any avenue for addressing it directly, an affair can become a way of expressing that anger indirectly rather than confronting the underlying conflict.
This pattern connects back to the Weiser et al. anger category, and it is worth naming clearly: some affairs are not about desire at all. They are about retaliation, or a need to feel powerful in a dynamic where the person has felt powerless.
Life Event Triggers: When External Circumstances Create Vulnerability
Certain life events produce a psychological vulnerability that increases the likelihood of an affair regardless of the relationship's baseline health.
Grief, Illness, and Existential Restlessness
Grief and bereavement create emotional rawness and a search for comfort that can lead someone toward connection outside the relationship, particularly if the primary partner is also grieving and less available. Serious illness, whether the person's own or their partner's, sometimes triggers an existential restlessness: a confrontation with mortality that produces urgency around experiences the person feels they haven't had.
Major Transitions and the Postpartum Period
Major life transitions, a career change, children leaving home, retirement, can produce an identity disruption that some people respond to by seeking external validation or novelty. The postpartum period creates a significant shift in relational dynamics that some couples don't navigate well, and that vulnerability is real in both directions.
Deployment and Extended Separation
Extended deployment or prolonged physical separation creates distance that, for some people, produces emotional drift that eventually crosses a line. In clinical practice, these triggers don't excuse what happened. They do explain the timing, and understanding the timing is sometimes part of what the betrayed partner needs to make sense of why it happened when it did.
The Psychology of Self-Justification in Affairs
One of the most clinically relevant aspects of infidelity that rarely appears in explanatory articles is how people justify affairs to themselves while they're happening.
How Moral Disengagement Works
Albert Bandura's research on moral disengagement shows that people are capable of engaging in behaviour that violates their own stated values when they have access to a narrative that reframes it. In clinical practice, this shows up consistently with people who describe themselves as fundamentally honest, as someone who would never do this, and who nonetheless did.
The Internal Narratives That Sustain Affairs
Common self-narratives that sustain affairs include: my partner doesn't meet my needs and I've tried to say so; this is the first time I've felt understood in years; my partner and I are basically already over; I'm not hurting anyone as long as they don't find out.
These narratives do real psychological work. They allow someone to maintain a positive self-concept while engaging in behaviour that contradicts it.
Why the Person Who Cheated May Seem Genuinely Confused
This mechanism matters for the betrayed partner because it explains why the person who cheated may appear genuinely confused about how it happened, or may seem to believe a version of events that feels impossible to credit from the outside. The confusion is sometimes real. The narrative had been running long enough to feel true.
Frequently Asked Questions About Why People Cheat
Does Cheating Mean the Person Didn't Love Their Partner?
Not necessarily. Love and fidelity operate through different psychological systems, and someone can have a genuine attachment to their partner while making choices that contradict it. The affair is not proof that the love was absent. It is proof that the person made a choice to pursue something outside the relationship and to conceal it, and those are the relevant facts regardless of what else was true simultaneously.
Why Do People Cheat Even When They're Happy in a Relationship?
Affairs in stable relationships are more common than most people expect. Clinical work in this area consistently points to identity-related motivations rather than relationship ones: a search for confirmation of desirability, a response to midlife questioning, or a high need for novelty that a long-term relationship cannot indefinitely satisfy. Relationship quality is one factor in infidelity, but in a significant number of cases it is not the primary one. This is one of the more disorienting findings for betrayed partners, and one of the more important ones.
Can Attachment Style Predict Infidelity?
Attachment patterns are a relevant factor in infidelity research, though they are not deterministic. Avoidant attachment is associated with affairs that serve an intimacy function without full emotional exposure. Anxious attachment is associated with validation-seeking outside the relationship when reassurance feels unavailable internally. Understanding someone's attachment pattern can provide useful context for why an affair took the shape it did, without eliminating their responsibility for the choice.
Is Cheating Always a Reflection of Relationship Problems?
No. While relationship dissatisfaction does appear as a factor in many affairs, a meaningful proportion occur in relationships that are functioning well. Character-based patterns, situational vulnerability, attachment dynamics, and identity-related motivations can all produce infidelity independently of relationship quality. An affair is not automatically diagnostic of a failing relationship, though it always reflects a choice the person who cheated made.
Do Life Events Like Grief or Major Transitions Make Affairs More Likely?
They can. Grief, serious illness, major life transitions, and the postpartum period all create psychological vulnerability that increases the likelihood of an affair regardless of the relationship's baseline health. These triggers don't excuse what happened, but understanding the timing, particularly when the relationship had been solid before, is often part of what the betrayed partner needs to make fuller sense of what occurred.
Is Virtual Counselling Available in Alberta for People Processing Infidelity?
Yes. The Mental Health Clinic offers virtual counselling across Alberta, including Calgary, Edmonton, Red Deer, Lethbridge, and smaller communities throughout the province. Many Alberta benefits plans cover sessions with a registered psychologist or registered social worker, so checking your coverage before your first session is worthwhile.
Final Thoughts
Understanding why affairs happen does not change the fact that one did. What it can do is replace a story that feels entirely senseless with one that has context. For many people, that shift is the first step toward deciding whether a relationship can recover after infidelity and what happens next, in the relationship and in their own life.
Whether you're in Calgary, Edmonton, Lethbridge, or a smaller Alberta community, the psychology behind infidelity is not a justification. It is a more complete picture, and for many people trying to make sense of something that blindsided them, that picture matters.
If you are working through the aftermath of infidelity, speaking with a therapist can help you make sense of what happened and decide how you want to move forward. The Mental Health Clinic offers confidential virtual counselling across Alberta for individuals and couples navigating infidelity and relationship uncertainty using Emotionally Focused Therapy, Cognitive Behavioural Therapy, and Narrative Therapy.
You can book a free consultationto speak with a Marriage and Family Therapist to explore whether counselling feels like the right next step for you.
Educational Disclaimer
This article is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. If you're experiencing mental health concerns that interfere with your daily functioning, please reach out to a qualified mental health professional. If you're in crisis, contact your local crisis line or emergency services immediately.
