Inherently, we can be selfish when it comes to things like making money, getting a job, and even sex. To achieve these self-rewarding goals, most of us use a tit-for-tat strategy, participating in charity and social reciprocity. However, there is a small percentage of the population, known as “Machiavellians,” who are hardwired to use betrayal and backstabbing to meet their selfish goals, according to a study published in the journal Brain and Cognition.

Selfish people are coined “Machiavellian” after Niccolo Machiavelli, the 16th century Italian writer and diplomat who was notoriously for his clever tricks and deceitful nature. Those with a Machiavellian state of mind are hardwired to exploit others in a social situation for their own personal gain. This occurs even when they encounter people who are fair and cooperative.

Tamas Bereczkei and his team of Hungarian researchers at the University of Pécs scanned the brains of of people who scored high in Machiavellianism while they played a four-stage game of trust in order to observe their exploitative decision making processes. A total of 150 participants, both a mix of high and low scorers on Machiavellianism, played several times with different partners.

First, the participants were given five dollars worth of Hungarian currency and asked to decide how much to “invest” in their partner. Any money they invest was tripled as they passed it to their “partner.” The participants thought this was another student, but in reality it was a computer. The partner then chose how much to return, which was either pre-programmed to either be a fair amount (10 percent above or below the initial investment) or an unfair amount (about a third of the initial investment). For example, if a participant chose to invest $1.60, a fair return by the partner would be about $1.71, according to the study. A typical unfair return would be about $1.25.

After these transactions, the roles switched and the study participants became the trustees. Their (computer-controlled) partner made an investment, which was tripled, and the participant decided how much to return. This would allow them to either punish their partner for their unfairness or reciprocate their cooperation.

“Our results revealed that the social environment involving opportunities for exploiting others may be more demanding for Machiavellians who showed elevated brain activities in the fair condition (where the partner made a cooperative initiation) but not in the unfair condition,” wrote the researchers.

The findings revealed participants with Machiavellian-like personalities neither punished nor rewarded their partners. Unsurprisingly, they ended up with more money at the end of the game than their non-Machiavellian counterparts. The researchers attributed this to a difference in brain activity.

Using fMRI techniques, when the Machiavellians’ partner played fairly, they exhibited an unusually high activity in brain areas involved in inhibition, including the dorsolateral prefrontal cotex (located at the front of the brain), and creativity, such as the middle temporal gyrus (located near the ears). This suggests Machiavellians inhibited the natural instinct to reciprocate fairness, and subdued any emotional reaction while determining how to take advantage of their partner at the same time.

So why are some people selfish?

Because they’re hardwired to be. A similar 2012 study published in the journal Personality and Individual Differences found Machiavellians had higher brain activity compared to non-Machiavellians in several brain areas while playing a game of trust. The researchers suggest Machiavellians have certain cognitive and social skills that allow them to adapt to the challenges of their social environments. In other words, Machiavellians are always looking for opportunities to exploit other people.

So maybe you’re wondering if you’re a Machiavellian or in-between. You can take a test to see if your personality falls along the mix of narcissism and psychopathy, two traits known to indicate a selfish person, or in layman’s terms, a jerk.

Sources: Bereczkei T, Papp P, Kincses P et al. The neural basis of the Machiavellians’ decision making in fair and unfair situations. Brain and Cognition. 2015.

Czibor A and Bereczkei T. Machiavellian people’s success results from monitoring their partners. Personality and Individual Differences. 2012.