For those who aren’t yet familiar with the term, the Oxford Dictionary defines pettiness as “undue concern with trivial matters, especially of a small-minded or spiteful nature.”

Additionally, pettiness can be more subtle than classic revenge. A 2009 social experiment conducted at Harvard and the University of Virginia gathered groups of people to play a financial game.

In each group, one experimenter was placed specifically to cheat so that the other people playing would notice. The scientists discovered that when given the opportunity for a no-fault chance at revenge, everyone playing who was cheated took a chance at it.

Meaning everybody was angry over what happened to them, and everyone given the opportunity for revenge took it.

Danny Greeves, a UK-based physiotherapist and behavioral change coach specializing in resolving resentment, said that revenge and pettiness are common aspects in our interpersonal relationships because they both trigger the law of obligation.

This is also known as reciprocity, which is the practice of exchanging things for mutual benefit. "Reciprocity is one of the universal principles which creates automatic, unconscious responses. It is the principle of mutual exchange," he explained, adding that in our evolutionary past, reciprocity was a vital principle because we relied on other people to assist us through fair exchange in order to do tasks and get basic human needs met.

Speaking plainly, when someone does something for us, we feel an obligation to return the favor.

"The pull of returning the action performed towards us is so strong because it has been crucial to our evolutionary progress," Greeves said.

This part of our nature is actually the reason why we feel rude when we don't say thank you, mean when we don't offer something we could share, or guilty when we don't do something we’re supposed to.

However, a paper published in the Journal of Experimental Psychology showed that petty behaviors made people seem less likable, even when the actions clearly benefitted others.

"Being precise isn't always a good thing for the quality of relationships," said study co-author Tami Kim, an assistant professor of marketing at the University of Virginia’s Darden School of Business. “Sometimes, leaving a little room for error might be a good idea.”

This applies to all sorts of relationships and has been proven numerous times under different circumstances. It even applies to people in romantic relationships — when they were asked questions about their partner's pettiness and their relationship satisfaction, researchers found a correlation between reported partner pettiness and unhappiness in a relationship.

So I guess a part of us wants to know there's still forgiveness in the world, after all.

"The downfall of pettiness can happen across many types of relationships, even amongst people who have been together for a long time,” Kim said. “Pay attention to the ways even the simplest behavior can be interpreted.”