“Pineapple on pizza” was searched more this February than it has been since Google started collecting search trend data in 2004. This sudden uptick in interest started when Icelandic President Guðni Th. Jóhannesson, in response to a question asked by a high school student, joked that he would make it illegal for people to eat pizza with pineapple on it if he could. A heated debate about the merits of pineapple on pizza and the limits of executive power then began on Twitter and other social media platforms. A great variety of news outlets reported on the controversy; for example, The New York Times published an article titled “Pineapple Pizza Tests Limits of Presidential Power in Iceland” and Eater published an article called “President of Iceland Wishes Death Upon Pineapple Pizza.” Even Canadian Prime Minister Justin Trudeau tweeted his support for Hawaiian pizza (which was invented in Canada). Jóhannesson’s statement became so controversial he felt compelled to apologize on Facebook in both English and Icelandic in a post titled “a statement on the pizza-controversy.” The official statement reads:

I like pineapples, just not on pizza. I do not have the power to make laws which forbid people to put pineapples on their pizza. I am glad that I do not hold such power. Presidents should not have unlimited power. I would not want to hold this position if I could pass laws forbidding that which I don’t like. I would not want to live in such a country. For pizzas, I recommend seafood.

The post focused on people’s concern about his overstepping the limits on presidential power, but the most prominent conflict he tapped into seems to have been over the merits of pineapple as a pizza topping. Fox News surveyed 2,193 people in 2016 and found that pineapple was, on average, people’s third least favorite pizza topping. In January, Twitter user @OriginalSDM posted two pictures of a piece of pizza covered in pineapple, asking his followers to “retweet to ruin a pineapple on pizza haters timeline.” The post was retweeted over 122,000 times. Responses ranged from supportive to comments like “I hope you go to prison.” The debate on Twitter was reignited again in March when Twitter user @Try2ShootUsDown posted a picture of a pizza she had ordered. The box had a note allegedly written by the employee who prepared it, which said, “Couldn’t bring myself to put pineapple on it. That’s gross. Sorry.” Five dollars were attached as compensation. Only two days after it was posted, the tweet had 63,561 retweets and 170,925 likes.

This incident is not the first time a conflict about pizza has taken up excessive amounts of media attention. There exists, for instance, a long-standing debate between Chicago and New York on who has the better pizza. Chicago pizza, also known as deep-dish pizza, has thick crust and is often eaten with a fork and knife, whereas New York pizza is thin-crusted and eaten with the hands. In a segment from The Daily Show in 2013, famous New Yorker Jon Stewart lambasted Chicago pizza, referring to deep-dish as “an above-ground marinara swimming pool for rats” before using other colorful descriptors. Political leaders got involved in this conflict, too: Chicago Mayor Rahm Emanuel sent Stewart two deep dish pizzas topped with anchovies. The attached note read, “Deep Dish With Dead Fish.”

Debates about pizza seem harmless enough, but the more complex aspects of the human psyche emerges through these conflicts. Such disagreements shed light on the way opinions polarize groups of people. When looking at a controversial political issue, as opposed to pizza preference, it is easier to understand why individuals might express passionate—often divisive—opinions on the internet. More difficult tasks are explaining why people become hostile (however jokingly) over something as trivial as a pizza topping, or why people feel compelled to take hard-line stances on issues they are not familiar with. With respect to the pizza debate, one could argue the discussion is purely fun and nothing about the conflict should be taken seriously. This answer belies a deeper question: why do people find it fun to take such a hard-line position on a trivial issue and then argue about it online?

One applicable concept from social psychology is “attitude polarization,” a phenomenon where members of a group form more extreme opinions on a topic than they would have independently. A 2010 study on attitude polarization on Twitter found that seeing others express the same opinion as oneself reinforces a feeling of group identity. Discussion between individuals with different opinions also reinforces group identity and tends to increase allegiance to one’s original opinion.

A 1995 paper by Roy Baumeister and Mark Leary argues that the need to belong to a group is a fundamental human psychological need. When people get involved in debates about pizza toppings or hometown superiority, they are reinforcing that feeling of group identity. Therefore, analyzing the social dynamics of more trivial conflict can be useful for understanding general psychological mechanisms that underlie higher-stakes conflicts that tend towards polarization.

Understanding polarization, especially the way it is reinforced by social media, all the more important in our current political climate. In 2004, Pew Research Center found that significantly more people identify as either “mostly or consistently conservative” or “mostly or consistently liberal” than in 2004. Another Pew survey found that, for the first time in 25 years, Republicans and Democrats have “very unfavorable” opinions of the other party instead of the usual “unfavorable.” Large majorities of both parties even said the other party makes them “afraid.” When asked to rate the other party’s 2016 presidential candidate on a scale of 1-100, on average, neither party rated the other’s candidate above 12.

People have blamed social media “echo chambers” for such increased partisanship. A 2014 study found that Twitter users are disproportionately exposed to information that confirms their opinions. From these results, some have extrapolated that increasing exposure to agreement and limited exposure to disagreement is causing polarization. While this theory might have truth, the insight that disagreement can also strengthen partisan beliefs makes the issue more complicated. In the pineapple-on-pizza debate, the posts by @OriginalSDM and @Try2ShootUsDown seemed to inspire and prolong controversy. The popularity of the posts does, however, support the idea that social media can quicken the pace of the attitude polarization feedback-loop by instantly connecting us with people who both share and do not share our views. When news circulates among massive volumes of people more quickly than ever before, group size and identity strength can increase just as rapidly.

Prominent examples of posts and statements that inspired pizza-related controversy closely resemble popular partisan behaviors in the media. Much of Jon Stewart’s diatribe on Chicago pizza focuses not on the qualities of the pizza, but on whether or not it can be considered pizza in the first place. Donald Trump uses a similar strategy when he claims that CNN and The New York Times are “fake news.” Both Stewart and Trump attempt to entirely discredit the other side’s right to enter the debate rather than address the nuances of an issue.

The post by @Try2ShootUsDown may be an example of a fake or exaggerated story meant to demonize the opposing side. The fact that the money appears to have been touching the pizza, which could get a restaurant accused of unsanitary practices, as well as the profit incentive a restaurant and its employees have that would discourage them from giving $5 back to a customer, put the post’s veracity into question. Especially during the 2016 election, many websites posted fake news stories often intended to intensify animosity towards the opposing political party. For example, on the most recent election day, the Conservative Daily Post claimed Barack Obama and Hillary Clinton were promising to give amnesty to undocumented immigrants if the immigrants voted Democrat. Other popular fake stories included one about the Pope endorsing Trump and another which said that Hillary Clinton sold weapons to ISIS.

The story of Jon Stewart’s attack on Chicago pizza has a happy ending. Marc Malnati, owner of Chicago pizza franchise Lou Malnati’s, went on Stewart’s show to personally deliver him a piece of Chicago pizza. The New York crowd booed, but Stewart tried the pizza and said it was “very tasty.” He also apologized for his previous comments. This is a relatively light example of someone reconciling with the out-group, or the group they do not belong to, after confronting an out-group member in person.

Group polarization via social media is powerful, but if New York and Chicago pizza fans can learn to get along, maybe there’s hope for the rest of us, too. It’s also possible that the next big internet debate will be over President Jóhannesson’s endorsement of putting seafood on pizza. According to the aforementioned Fox News survey, anchovies were people’s overall least favorite pizza topping and were, unlike pineapple, not included in the list of people’s favorites. Now that seafood pizza now has a public supporter, maybe it will be spotlighted in the next big pizza controversythat is, if the pineapple drama cools down.