No end of the affair

What causes people like John Terry to play away from home? The reasons we have affairs could be down to our biology
January 27, 2010
Got you under my skin: Celia Johnson and Trevor Howard in David Lean’s Brief Encounter (1945)


Extramarital affairs have always been risky. And it is a commonplace that today’s technologies, while making it easier to conduct a liaison, almost guarantee discovery thanks to itemised bank statements, timed till receipts, text messages and so on. Even worse, you cannot play down the seriousness of it because “sweet nothings” can be retrieved from voicemail or emails. With this level of surveillance, surely no sensible person who values their marriage would ever transgress. So why do they?

As a marital therapist, I have spent years trying to answer this question. The psychological factors are well understood. The widely known theory of “compartmentalisation” (a term coined in the 1940s by Karen Horney, founder of the American Journal for Psychoanalysis) often explains how unfaithful partners justify their behaviour. To some extent, we all build walls to section off parts of our life. When we compartmentalise, these two worlds become sealed boxes where the action in one world, supposedly, has no impact in the other. Hence someone who is unfaithful will say: “It helps me deal with stress,” and deny the impact on their partner or family. Plus, they imagine an affair will not be discovered: after all, it’s happening in a separate place.

Of course, people have affairs for countless individual reasons: family history, addiction, sexual orientation, desire for revenge and so on. It can even be an accident. But recent findings from a new discipline called neuroesthetics—which seeks to understand our appreciation of art at a neurological level—and from neuroscience itself, are giving scientific credence to some things we know instinctively about love.



Received wisdom has always held our notions of romantic love to be cultural and social, but research by Semir Zeki, professor of neuroesthetics at UCL, suggests something different. The brain’s job is to process knowledge that is either biologically inherited or acquired through learning. We are born with inherited concepts, such as an understanding of colour, which are almost impossible to ignore or disobey. But the acquired ones—like recognising a car from any angle—come from experience and can therefore be continually modified and updated. Zeki thinks that our guiding principles about romantic love are not acquired, but inherited.

Zeki specialises in the anatomical and physiological study of the primate visual brain, and measures blood flow to certain regions using fMRI and PET scanners. But in his latest book, Splendours and Miseries of the Brain, he combined his scientific knowledge of how the brain functions with direct evidence from its output—sculpture, painting, literature, music and dance over the last millennia. He found that humans share universal myths about love which vary “little, if at all, from one culture to the next or with time.” As many of these myths cannot have been transmitted culturally (say, between medieval England and China) they must have a common biological heritage.

Similarly, the fundamental concept behind the emotion of love—that of “unity-in-love”—is also inherited rather than learned; and it is this that compels us towards passionate sexual relationships, as intercourse is the nearest we can get to merging with another individual. We pursue this union with such a force because it is biologically ingrained in our brains. Unfortunately, everyday married life—earning a living, running a home and raising a family—is often at odds with our brain’s idea of unity-in-love. The passion of an affair, on the other hand, binds forbidden lovers together in a way which replicates our inherited concept of love and overrules any acquired ideas that it is wrong.

This may help us understand how affairs are started, but why, once begun, are they so difficult to end? In 2000, Zeki’s colleague, Andreas Bartels, scanned the brains of students who were “truly, deeply, madly in love” and showed them a photograph of their beloved. He then compared the results with subjects who used cocaine or opiods, and discovered that many of the same regions of the brain became active, especially those responsible for emotion (insular cortex), reward anticipation (anterior cingulate cortex), and memory (caudate nucleus). Lovers also show three classic symptoms of addiction: tolerance, withdrawal and relapse. At the beginning of an affair, lovers meet occasionally but as the addiction escalates they need more and more of their drug (being together) and complain: “I can’t get enough of you.” Finally, despite all the attempts to stop before the infidelity is discovered, they relapse like drug addicts because something—a favourite song, visiting an old haunt—triggers the need for another high.

This helps make sense of my own research—completed by 358 self-selected adulterers via my website—which reveals that the most common crisis point for a long-term relationship is 24 years. It seems that watching our children discover “unity-in-love” and its compulsive nature reawakens our own desires and may make long-term partnerships feel somehow lacking.

Therapists should never take sides, yet my patience has been tested when someone has claimed “I couldn’t help it,” and I’ve wondered how they could be so stupid. But, given what we now know about the brain, perhaps we all need to be more realistic and forgiving. Whatever tax breaks or laws politicians promise to promote marriage, and however much we wish to keep our vows, some of us will be ambushed by the nature and chemistry of love.