The way you were loved — or not loved — as a child creates a neurological template that operates in every adult relationship. Attachment theory, developed by John Bowlby and extended by researchers across five decades, reveals that infidelity patterns are almost entirely predictable from early attachment history.
Comfortable with intimacy and independence. Can ask for needs directly. Lowest infidelity rates. Partners feel safe and seen.
Fear of abandonment, hypervigilant to rejection cues. May seek outside validation when feeling insecure in the relationship.
Discomfort with closeness. Equates intimacy with loss of self. Most likely to compartmentalise affairs — no emotional threat to autonomy.
Trauma-based. Simultaneously craves and fears intimacy. Highest rates of infidelity and relationship instability.
The anxiously attached person lives with a persistent background hum of "am I loved enough? Will they leave?" Their nervous system is calibrated for threat detection — and every moment of emotional distance from their partner registers as danger. When a primary partner is unavailable, dismissive, or simply busy, the anxious brain does not interpret this as neutral. It interprets it as evidence of abandonment.
The outside relationship provides what researchers Fraley and Davis call proximity maintenance under threat — relief from the anxiety through an alternative attachment figure. The anxiously attached person is typically not seeking sex. They are seeking reassurance that they are loveable and will not be abandoned. The outside person provides this, temporarily.
The avoidantly attached person has a different dynamic. They experience genuine intimacy as threatening — closeness activates their deactivating strategies, the neurological learned response of emotional shutdown. Affairs for avoidant individuals serve a structural function: they prevent any single person from getting close enough to threaten the defended self.
Dr. Phillip Shaver and Mario Mikulincer's research found avoidant individuals are more likely to engage in casual sex outside relationships specifically because it involves no emotional risk. The compartmentalisation is not cynical — it is an unconscious self-protection strategy developed in response to early caregivers who punished emotional need.
Disorganised attachment (also called fearful-avoidant) develops when the primary caregiver was simultaneously the source of safety and of fear — typically in cases of abuse, neglect, or severe parental mental illness. The resulting neural architecture treats intimacy as inherently dangerous. These individuals simultaneously desperately want love and are convinced, at a deep level, that love will hurt them.
Research by Mary Main shows that disorganised attachment is the single strongest predictor of both infidelity and the inability to leave relationships that are harmful. The person creates the very abandonment they fear — by betraying first.
The most important finding in attachment research is this: attachment style is not destiny. Dr. Mary Ainsworth's late research and subsequent work by Siegel, Fonagy, and others documented the concept of earned security — insecure adults who develop secure attachment through therapy, secure relationships, or deliberate self-awareness. Recognising your attachment pattern is the beginning of not being enslaved by it.