As anyone who has ever been passionate about a particular sports team knows, the other side has a habit of playing dirty and the referees tend to make unfair calls. But the secret is that this happens on both sides.

The year is 1951. In what is probably the most-studied football game in the history of psychology⁠, Dartmouth traveled to Palmer Stadium in New Jersey on November 23, 1951 to play Princeton. By all accounts possible, it was an ugly game. The star of the show—Princeton’s Kazmaier, had been featured on the November 19, 1951 cover of Time magazine, the caption reading: “From a single wing, a triple threat.”

Kazmaier left early after sustaining a concussion and breaking his nose. Dartmouth also saw its share of injuries, including a broken leg.

Nearly all Princeton students judged the game as “rough and dirty”—not one of them thought it “clean and fair.”

Later, researchers showed students from both schools clips of the game and asked what they saw.

When Princeton students saw penalties:

• •the ratio of Princeton’s flagrant to mild penalties was 1:3
• the ratio of Dartmouth’s flagrant to mild penalties was 2:1

When Dartmouth students saw those same penalties:

• the ratio of Princeton’s flagrant to mild penalties was 1:2
• the ratio of Dartmouth’s flagrant to mild penalties was 1:1

Dartmouth fans had a much easier time justifying their team’s violent behaviors. And Princeton wasn’t innocent, either: in the third quarter, a Dartmouth player was taken off the field with a broken leg.

The feedback we get about our assessments starts with how a decision feels. Is there anything more ambiguous than the social world—especially sports? And is there anything easier than justifying the actions of our own ingroup?

And then, it’s reinforced through our social groups. It’s how our habits get reinforced. Social feedback is why Dartmouth fans—all of them surrounded by other Dartmouth fans they were motivated to maintain a bond with—thought that Princeton started playing dirty in that infamous 1951 game. Social feedback is why you’re more likely to love a song if your best friend loves it. Even when we’re looking at a football game and trying to decide which team started the ruckus, what we see is never purely objective.

Light doesn’t directly pass through to the visual cortex. First, it has to run through the orbitofrontal cortex. The OFC is thought to be the link that interprets external and internal sensory information and figures out how to guide our behavior, measuring the “outcome value.” Leading neuroscientist Luiz Pessoa once argued that “Vision is never pure, but only affective, vision.” Everything we see first passes through a lens that plays a role in how we evaluate objects and helps assign value to environmental stimuli. Emotions, preconceptions, or feelings are integral to the way we process information.

And then, after we see something passing through that lens, our decisions and evaluations get reinforced externally. If we think that our coworkers will approve of the hire, or our parents and friends will be on board with a new romantic interest, or if our fellow fans agree. From our brain’s perspective, feeling like we’ve come to the right conclusion is its own kind of reward—one that’s surprisingly removed from the more important question of whether or not we’re actually right.

So was the Super Bowl fair? That depends on who you wanted to win, and who actually won.