A stranger carries no disappointments, no arguments, no habits that irritate. They are a blank canvas the brain paints with perfection. Understanding why this happens is the key to not being destroyed by it.
When you meet someone new who triggers attraction, your brain releases a cascade of dopamine — the same neurotransmitter activated by cocaine, gambling, and sugar. The brain's reward circuitry (the nucleus accumbens) does not distinguish between healthy and unhealthy sources of dopamine. It simply registers: this feels extraordinary.
Neuroscientist Dr. Helen Fisher (Rutgers University) used fMRI imaging to show that newly attracted individuals have brain activity virtually identical to early-stage cocaine addiction. The anterior cingulate cortex — responsible for obsessive focus — activates intensely. You cannot stop thinking about the person. This is not love. This is a chemical storm.
The stranger is not who you think they are. Your brain, with minimal data, projects an idealised version onto them. This is called projection fantasy — the mind fills in every unknown detail with something desirable. The existing partner, by contrast, is fully known: their snoring, their moods, their flaws. The comparison is fundamentally unfair.
Psychologist Dr. Shirley Glass, author of Not Just Friends, documented how affairs almost always begin with a "comparison illusion" — the outside person is compared to the worst version of the partner (stressed, tired, arguing) rather than their real self. The stranger has no bad days in your imagination yet.
Long-term relationships accumulate what psychologists call negative sentiment override — a state where even neutral interactions are interpreted negatively because of the history of conflicts. A partner saying "how was your day?" can feel like an interrogation after months of tension.
A stranger has none of this accumulated charge. Every interaction is unburdened. Dr. John Gottman's research at the University of Washington found that couples in distress have a 5:1 ratio of negative to positive interactions — meaning the emotional ledger is deeply in debt. A stranger starts at zero.
Clandestine contact activates the brain's fear/arousal system simultaneously with its reward system. Adrenaline and dopamine co-release creates an exceptionally powerful neurochemical state. Research from the Journal of Personality and Social Psychology (Aron et al., 2000) demonstrated that danger and novelty dramatically amplify attraction — the "misattribution of arousal" effect.
In plain language: the forbidden nature of outside contact is itself part of the attraction. If it were permitted, much of the charge would dissolve. This explains why many affairs, when they become the primary relationship, quickly lose their intensity.
Dating apps have industrialised the stranger effect. Each new profile delivers a micro-dopamine hit. The infinite scroll creates what psychologist Dr. Sherry Turkle calls a "robotic moment" — the preference for curated, controllable connection over the messy reality of deep relationship. People in committed relationships report that even passive app browsing activates the dopamine system and produces comparative dissatisfaction with their partner.
The brain neurologically rewards novel stimuli. New faces activate the substantia nigra/VTA region that floods the brain with dopamine.
Known partners are compared at their worst; strangers at their imagined best. The comparison is a cognitive distortion, not reality.
Secrecy + adrenaline + dopamine = a neurochemical state stronger than most experiences in settled life.
Research shows 80%+ of affair partners, when they become primary relationships, report the same dissatisfactions within 2 years.
Understanding the stranger effect reveals that the pull toward outside intimacy is not primarily about the outside person — it is about the state of the internal neurochemical life. Stable, high-dopamine relationships have built-in novelty: new experiences, physical variety within the relationship, emotional surprise. Research consistently shows that couples who regularly introduce genuine novelty into their relationship (new travel, new activities, new conversations) maintain attraction far longer.
The most devastating insight from Dr. Perel's work: the person who has an affair is rarely running toward something. They are overwhelmingly running away from something — boredom, invisibility, an unexamined life.
Fisher H. (2004). Why We Love. Aron et al. (2000). Reward, motivation and emotion. Gottman J. (1994). Why Marriages Succeed or Fail. Perel E. (2006). Mating in Captivity. Glass S. (2003). Not Just Friends.