Anger is the flash of fire that sparks in your brain when you feel you have been shortchanged. Perhaps a stranger has nipped into the parking space that you had been about to occupy, or a lazy work colleague has landed you with a thankless task. Or maybe you have been confronted with a deep, hurtful betrayal by someone you love.

Anger is one of the most primitive emotions we experience – animals are equipped with the same basic neural circuitry. It operates on a spectrum from mild frustration to absolute fury, and the intensity with which we feel anger and how we act on it is very personal. Science is beginning to provide new explanations about the ways that personality, age, gender and life experiences shape the way we feel this emotion.

What is anger?

Scientists believe that the capacity for anger has been hardwired into the brain over millions of years of evolution. It forms part of our instinct to fight off threats, to compete for resources and to enforce social norms. Anger is rooted in the brain’s reward circuit. We are constantly – often subconsciously – weighing up what we expect to happen in any situation. When there is a mismatch between what we’ve learned to expect and the hand we’re dealt, our brain’s reward circuit sounds the alarm and activity is triggered in a small almond-shaped region in the brain called the amygdala.

Anger can trigger the body’s fight or flight response, causing the adrenal glands to flood the body with stress hormones, such as adrenaline, and testosterone, preparing us for physical aggression. But whether we actually end up swearing or scowling or even punching someone depends on a second brain area, the prefrontal cortex, that is responsible for decision-making and reasoning. This puts our anger in context, reminds us to behave in socially acceptable ways and for most of us, most of the time, keeps our primal instincts in check.

How does anger change the way we think?

Feeling anger can alter the way we view risks. Studies have shown that it can make us more impulsive and make us underestimate the chances of bad outcomes. In one study, volunteers who were made to feel angry estimated the chances of suffering heart disease as being lower and said they were more likely to receive a pay raise, when compared with volunteers who had been prompted to feel fearful. Depending on the context, anger can make us brave or reckless.

[People are angrier when they lose sleep, study says]

Anger also influences group dynamics. When we feel angry, we tend to think more negatively and in a more prejudiced way about outsiders, becoming more likely to blame negative traits on a person’s nature rather than their circumstances. Angry people tend to seek someone to blame, research shows. This potentially makes an angry person feel even more enraged with the offending person or group, in some cases perpetuating a spiral of irrational rage.

Does anger have benefits?

Anger has been viewed fairly negatively over the course of history. In ancient Greece, Seneca pronounced anger "worthless even for war", while wrath makes it on to the list of deadly sins. But science suggests there could be some benefits for the angry individual, if not for society at large.

Anger can serve as a powerful motivator. In a 2010 study, Dutch scientists showed volunteers pictures of objects such as pens and mugs on a computer screen interspersed with subliminal images of angry or neutral faces. When an angry face had flashed up first, people rated objects as more desirable and worked harder to win them in a subsequent game. Interestingly, the participants were not consciously aware of this motivation – they said they just liked the objects more.

Outward expressions of anger can also alter the way you are perceived. Larissa Tiedens, an American psychologist who has conducted extensive research on anger, found that participants were more supportive of President Bill Clinton when they viewed him expressing anger about the Monica Lewinsky scandal than when they saw him expressing sadness – and the effect was replicated with an unknown politician.

Tiedens also found that participants assigned a higher status position and salary to a job candidate who described himself as angry as opposed to sad. And showing anger during a negotiation has also been shown to increase the chances of succeeding in it – people are more likely to yield to someone who is perceived as stubborn, dominant. It’s worth noting that these studies related to how angry men are regarded – there is some evidence that people view angry women less favourably.

Are men more angry than women?

Men are, on average, more outwardly aggressive than women and so it might be assumed that they are also angrier. But this doesn’t appear to be the case. Research has consistently found that women experience anger as frequently and as intensely as men. Men who feel angry are more likely to display aggression, although this does not mean that women are not motivated by rage as frequently.

One study, by scientists at Southwest Missouri State University, who surveyed around 200 men and women, suggested that women were as angry and acted on their anger as frequently as men. The main difference they identified was that men felt less effective when forced to contain their anger, while women seemed better able to control immediate impulsive responses to anger.

Some have suggested that these gender differences are rooted in underlying differences in brain biology. One study, by Ruben and Raquel Gur, a husband and wife team at the University of Pennsylvania School of Medicine, found that while the amygdala is a similar size in men and women, a second region, called the orbital frontal cortex, which is involved in controlling aggressive impulses, is much larger in women. They suggested this could help explain why women seem to be better at keeping the lid on explosive outbursts.

The jury is still out on the extent to which brain biology explains gender differences in terms of anger, but also other behaviours, and there is also compelling evidence that societal expectations play a part.

‘We know that even how teachers treat girls and boys in school is quite different and that could influence the ability to regulate these responses,’ says Arielle Baskin-Sommers, a psychologist at Yale University. ‘It’s never going to be just the brain that explains these differences, it’s 100 per cent more complicated than that.’

Why do toddlers get so angry – and what can parents do about it?

Being a toddler is an exciting time: everything is new and there’s so much to explore. But this means, unlike adults, they don’t yet have a well-developed framework of how things work and what to expect from life. They also often lack the language skills to explain what they want. So missteps as trivial as slicing a piece of toast incorrectly can trigger a nuclear intensity meltdown.

For parents, tantrums are a source of utter dread. But Michael Potegal, a psychologist at the University of Minnesota, decided to treat them as natural phenomena, rather like thunderstorms or volcanic eruptions, that could be analysed and understood.

Potegal and colleagues recorded toddlers in their everyday lives, capturing the audio of more than a hundred tantrums. They found that tantrums followed a predictable trajectory that could be boiled down to a combination of two emotions: anger (screaming, yelling, throwing things) and sadness (crying, whining, lying on the floor).

Sad sounds were found to be a constant undercurrent throughout the tantrum, while anger tended to build up to a peak and then vanish, the researchers found.

The trick to ending a tantrum, the scientists concluded, is to get the child over the anger peak as quickly as possible and the trick to that was ... doing nothing. Even intervening to ask what was wrong appeared to prolong the process.

Mental health and anger

Our response to angry feelings depends on finely balanced communication between several brain regions. When this becomes disrupted, people’s behaviour can become unexpectedly aggressive.

Neurodegenerative diseases, such as Alzheimer’s and particularly frontotemporal dementia, can result in damage to the brain’s frontal regions that inhibits our instinctive response to frustration and anger and also a breakdown in connections between this area and the amygdala.

Luca Passamonti, a consultant neurologist and researcher at the University of Cambridge, says: ‘On average we know that people with frontotemporal dementia will become more aggressive, angrier, grumpier. It makes these feelings more manifest and the way of expressing it can become really impulsive.’

Passamonti says this is likely to be a mixture of losing the ability to inhibit automatic responses to frustration, but also finding it harder to contextualise emotions and understand why you are feeling a certain way.

The way we process angry feelings also contributes to our mental well-being. Passamonti says that in some people, high levels of inhibition – an unusually active frontal cortex – can prevent expressions of anger, but result in people feeling depressed.

Finally, life experience also shapes the way people experience anger. ‘There’s a lot of research showing that exposure to violence ... is correlated with romanticising anger and aggression,’ says Baskin-Sommers, whose research covers criminal and antisocial behaviours.

A recent study, aimed at uncovering how exposure to violence changes people’s cognitive processes, found that people who had violent childhoods were able to discriminate between "good" and "bad" strangers in an experiment. But they were less likely to trust people, even when they had behaved generously. "It shapes them so fundamentally that they’re not able to easily discriminate who they can trust," says Baskin-Sommers. "They’re always on edge and unsure how to navigate that social world."

That constant feeling of threat means anger and aggression can be triggered far more easily. In the future, Baskin-Sommers says, interventions such as cognitive behavioural therapy could help people overcome early life experiences such as exposure to violence.

Guardian News & Media