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We humans are masters of resentment—a characteristic that can be traced back the beginnings of recorded history. Feuds seem to be an indelible aspect of the human condition, but why should this be? We spoke to the experts to find out why we love to hold a grudge, and the importance of letting go.




Like other emotions, the capacity for hate and resentment are learned and reinforced over the course of our lives—but they’re also etched in the wiring of our DNA. When we boil feelings of resentment and the desire for revenge down to the most basic level, they’re really about an evolved mental state that’s driving us to achieve some sort of goal. Ultimately, feuds are rooted in desire, and the seeking of a particular outcome.

“The really deep satisfaction comes from knowing that the person who harmed us has realized they wronged us, that they’re being punished, and they’re now going to change their ways.”


In the brain, it’s the behavioral activation system that gets us all roused up, specifically in the way it compels us to pursue and achieve goals. In neurological terms, it involves several brain structures, including the substantia nigra, a midbrain area involved in reward; the ventral tegmental area, a structure that produces and transmits dopamine; the ventral striatum, which is associated with reward, reinforcement, and compulsion; and the prefrontal cortex, the front part of our brain, which, among many other things, helps us to work toward a defined goal.

The physiological processes involved in the behavioral activation system are poorly understood, but it’s likely facilitated by dopamine—a neurotransmitter linked to reward, reinforcement, and positive feelings. This system is very much in play when we’re embroiled in a feud we’d like to win, or when we wish to lash out at someone who’s harmed us. Michael McCullough, a professor of psychology at the University of Miami, said grudges, and the desire for revenge or absolution, are directly related to goal-seeking and the desire to satiate a craving.

“This ancient brain system seems to produce this craving, and the sense that fulfillment is just around the corner,” said McCullough. “It’s not the seeking of pleasure or the reward itself, but rather the desire to move towards that goal It’s the sense of unease that gives the desire for revenge its compulsive quality.”

So when we’re having a feud with someone, we’re really in a perpetual state of craving or desire. It becomes important for us—sometimes to the point of obsession—to make sure the person behind our angst will change their mind, acknowledge their faults, understand the harm they’ve done to us, and/or and ultimately learn a lesson. Or in some cases, we feel the need to either verbally or physically harm the other person, in a tit-for-tat sort of way, according to McCullough.


“The really deep satisfaction comes from knowing that the person who harmed us has realized they wronged us, that they’re being punished, and they’re now going to change their ways,” said McCullough. “Those are the key set of conditions that makes revenge seem pleasurable—the sense that some kind of karmic justice is being meted out.”



But there’s a lot more going on in the brain during a feud than just cravings; in order to have a grudge, we must ruminate (i.e. dwell on the matter), which, in addition to taking up a lot of our time, requires a lot of brain power.


To demonstrate this, neuroscientists from the University of New South Wales insulted participants who were having their brains scanned in an fMRI. During the initial burst of anger, the scientists watched as the medial prefrontal cortex (decision making, retrieving of memory) lit up like a Christmas tree. Two weeks later, the participants were brought back and asked to think about the experience and how they felt about the insults. Different parts of the brain were activated during this later stage, including the hippocampus (consolidating information and converting short-term memory to long-term memory), the insula (a small part of the brain linked to emotion and addiction), and the the cingulate cortex (various functions involving emotions). Grudges and angry thoughts, as this study points out, are neurologically complex processes.

The utility of anger

But these emotions exist for a reason. Carrying a grudge, and wanting to seek revenge, shows we’re not pushovers. And in some cases, the expression of these feelings, and acting upon them, can be a means to an end.




“Humans,” said McCullough, “have a propensity for anger, grudges, and revenge when they’re harmed.” The capacity for revenge, he said, is a built-in feature of human nature—expressions that sometimes serve to solve problems, particularly the problems that arise from living around other people. One of the more fascinating aspects of feuds and the desire for revenge, said McCullough, is its universality across human culture. Concepts of resentment, feuds, and revenge appear in approximately 95 percent of all ethnographic material on all the societies studied by anthropologists, psychologists, and behavioral scientists, according to McCullough.

Independent lines of evidence suggest other species have acquired similar habits, such as retaliatory violence, threats of retaliatory violence, and grudge-like behavior. Ravens, for example, can hold grudges lasting from days to even a month. Chimps also hold grudges. Ultimately, the purpose of these actions is to deter future harm, according to McCullough. Game theory has also shown that the threat of retaliation is good at creating deterrence. Holding a grudge, and then acting on that feeling, can be a successful strategy in some cases.


“In terms of what these feelings are good for,” said McCullough, “the best answer on the table is that we experience a desire for conflict or revenge when we perceive that we, or our loved ones, are undervalued, or not given the respect we deserve from an interactive party. It also shows that we’re not going to take mistreatment lightly, so it’s like we’re imposing a kind of tax on people who we feel have done us wrong.”

Disputes, feuds, and grudges are rooted in anger, with the emotion of anger serving to prepare us to fight, explains neuroscientist Doug Fields, chief of the Nervous System Development and Plasticity Section at the National Institutes of Health and author of Why We Snap. Fighting is a necessary behavior in the survival-of-the-fittest struggle in nature, he said, and it remains necessary in some dire situations in the modern world.


Serious costs

But feuds and grudges come at a considerable mental cost.

A 2007 study co-authored by McCullough found that people who are stewing about something produce higher levels of cortisol than usual. Too much of this stress hormone in the brain can result in anxiety, depression, trouble sleeping, memory and concentration problems, and even weight gain. In 2012, McCullough published a followup study showing that cortisol levels linked to an interpersonal conflict decrease when we make conciliatory gestures toward the person who hurt us; forgiveness can be a very powerful thing—even within the circuits of the brain.


“These thoughts take up a lot of disk space. These are opportunity costs, and it means that are a billion other things you can’t be thinking about.”

But there’s another cost associated with rumination, and it has to do with our behavior. A 2005 study published in the Journal of Personality and Social Psychology showed that holding a grudge and dwelling on anger is particularly harmful because it increases aggression over extended periods of time—even toward people who have nothing to do with the feud or grudge. This form of aggression, according to a 2013 study, happens when “our efforts to reach a desired goal are thwarted.” In other words, when we’re frustrated.


Indeed, feuds and grudges can be very detrimental to the individual, and they can take on a compulsive quality. When we’re stewing about something, we ruminate about how we were mistreated, and we obsess about things we wish we had done or said, or what we’re going to do.



“These thoughts take up a lot of disk space,” said McCullough, “These are opportunity costs, and it means that are a billion other things you can’t be thinking about. You can’t think about the nice relationships you currently have, and you can’t think about your future in a productive way, because you’re sitting around ruminating.”


Get over it

So while carrying a grudge may seem productive or somehow useful, it actually holds us back. We need to snap out of it. The key is to recognize the futility of it all.


“It’s important to understand the neurocircuitry of anger and aggression and realize that we have these biological responses because they are sometimes necessary, but that often these circuits can misfire, especially in the modern world, an environment our brain was not designed to operate in,” said Fields. “Anger and aggression may be provoked inappropriately, and in such cases cannot help the situation, but may worsen it.”

Remember this the next time you’re mired in a feud that seems illogical and unreasonable, and yet you just can’t let go. It’s your brain that’s causing those feelings, not the other person. Recognize that, accurately evaluate the situation, and try to get over it.