"Treat others as you would want them to treat you" is the timeless golden rule. And it's not just a famous saying – most people actually do expect others to behave like they do themselves. A 2023 study found that selfish people punish generosity and reward selfish behavior. And, in turn, generous people tend to reward generous behavior.

"If everyone around me is selfish, then I'm going to learn to accept selfishness and behave accordingly," one of the study's authors, Paul Bogdan, Ph.D., commented on his and colleagues' findings. "We show that your judgments of other people's behavior really depend on how you behave yourself."

The researchers also found that people didn't give in to social pressure when it came to punishing either generosity or selfishness. Participants were guided by their own behavior rather than the pressure to conform. As the co-author of the paper Professor Florin Dolcos explained, we filter information about the world through our own filter.

The study also proves that we are drawn towards people who are more like us. As the participants offered to split a pot of money with each other, those who would give generous offers tended to accept offers from like-minded folks. And those who put their well-being first preferred to share the money with more selfish individuals.

If this list is making you lose all faith in humanity and its generosity, don't be alarmed. Some research suggests that altruism is intrinsic in our brains. In 2016, researchers from UCLA found that people might become less giving if an area of their prefrontal cortex is affected.

We also might assume that selfishness leads to earning more money and living a more comfortable life. It's logical: you dedicate more time to your career, have no children, and focus on your work, and voila – you're on top of the food chain. However, science says otherwise.

A 2020 study by a team of researchers from Stockholm University found that selfish people have fewer children and earn less money. While the public opinion remains that successful people are selfish (68% of the respondents said so), the data actually disproved this. People with selfless attitudes had more children and higher incomes. As they stated in the title of their paper, "Generosity pays."

So, if altruism and generosity are natural to us and benefit us more economically, why do we act like jerks? Psychologist Lisa Marie Bobby says that such behavior is a sign of low emotional intelligence. "One symptom of low emotional intelligence is the tendency to be self-absorbed, or exclusively concerned about what you're thinking, feeling, needing and wanting, instead of the thoughts, feelings, needs and desires of others."

Bobby explains that such behavior is often the product of upbringing. Those whose emotional needs weren't met in their formative years might grow up to be selfish and inconsiderate as adults. Those who are empathetic as adults, in contrast, grow up with their thoughts and feelings reflected back to them. "Thoughtful and compassionate people are not born, they're made," she observes.

When evaluating our own selfishness, our memory often works against us. As research by the psychologists at Yale University and the economists at the University of Zurich shows, we tend to misremember our selfish deeds. That way, we maintain our self-image. "The desire to preserve a moral self-image can be a powerful force and not only motivate us to rationalize our unethical actions, but also 'revise' such actions in our memory," senior author of the study Molly Crockett said.

Other researchers say that we ought to cut selfish folks some slack. Oftentimes, their behavior is the result of past mistreatment and betrayal. "We are quick to judge people and label them, especially when they behave in a way that appears unacceptable to us," Dr. Jerabek, president of PsychTests, says. "Maybe that person who cut you off in traffic, that customer who was rude to you, or that nitpicky colleague has more going on in their life than meets the eye."

We've got many more examples of people being inconsiderate in this series of ours. You can find the previous iterations of lists where people are being jerks here, here, here, here, and here. And, in the meantime, stay empathetic and considerate – you never know what the other person is going through, even if they're acting like a jerk. The world could always do with more kindness.