Why do sensible and rational people seem to lose the ability to act sensibly and rationally when they are in conflict? What makes some families tear themselves apart in a variety of squabbles which to outsiders may seem petty but which result in family members not speaking to each other for years? What drives neighbours to blight their daily lives with unpleasant, bitter and confrontational disputes? And how can otherwise placid and restrained people become almost unrecognisable when involved in road rage incidents – or even trolley rage in supermarkets?

The answer may be distilled down to one psychological phenomenon: self-esteem. It is one of the strongest motivating factors in conflict and generates powerful emotions. We all have self-esteem, whether corporate or individual; we all have a need to think well of ourselves, and for others to think well of us. Self-esteem governs many of the decisions we make daily, as we expend huge amounts of time and effort constantly maintaining and protecting our self-image.

The flipside of our desire for approval is our aversion to disapproval – or worse still, our dread of humiliation. An example of this is the fear of public speaking – a dread that can be greater than that of flying or even of death. It is explained by the fact that the disapproval of each person in the audience constitutes a potentially significant attack on our self-image. The larger the audience, the more overwhelming is the prospect of humiliation.

Our brains seem to indicate that saying sorry will be as painful as putting our hand into a fire

There is now neurological evidence demonstrating the effect that attacks on our self-esteem have on the brain. One study showed that “social pain” activated the same circuits of the brain as physical pain. Consequently any attack on our self-image is interpreted by the brain as physical pain. When we speak of “hurt” feelings, we acknowledge that any form of censure, from slight criticism to outright condemnation or rejection, affects our self-esteem and is felt as physical pain – hence our aversion to admitting fault or to accepting liability. The word “sorry” is one of the most difficult to express, despite it being the quickest, cheapest and most effective form of resolving a dispute. But our brain seems to indicate to us that saying sorry will be as painful as putting our hand into a fire.

The ability to monitor neural pathways helps us to see how our brain functions in conflict situations. For example, we now have a neurological explanation of our “fight or flight” instinct. This reflex is governed by the amygdala, two small structures in the brain that control our instinctive responses. Originally needed as a part of our evolutionary development, they enabled us to act swiftly and instinctively in the face of physical attacks in the wild.

Today the amygdala can be triggered by any attack on our self-esteem. When the brain perceives a threat, whether physical or on our self-image, the amygdala “takes control”, diverting the signals away from the cortex, the “thinking” part of the brain. This “amygdala hijack” prevents us from engaging in logical or analytical thought, instead creating instant defensive reactions.

That is why we recoil at any allegation of fault, whether in business, within the family, behind the wheel of a car – or in the supermarket. It is an assault on our self-esteem, and it is painful. It is at these moments that we need to shrink our egos, to tell ourselves that our self-esteem is unnecessarily getting in the way, and that it is far more productive to try to see things from the other’s perspective.

The Psychology of Conflict: Mediating in a Diverse World by Paul Randolph is published by Bloomsbury. To order a copy for £30, go to bookshop.theguardian.com