In November 1951, the Dartmouth and Princeton football teams played a season-ending game that resulted in a seminal work on the nature of human cognition.
Princeton won the contest, to finish the season undefeated. Of more lasting consequence, though, was the research that followed _ a psychological case study that provides a helpful overlay for today's politics.
The game was exceedingly violent, with broken bones and a flurry of penalty flags. Subsequent news accounts stoked the controversy, with fans from each side blaming the other for the mayhem.
Intrigued, a pair of researchers undertook an experiment in which students at the Ivy League colleges filled out questionnaires gauging their reactions to the game. The students were shown film clips of the scrimmage and asked to mark instances they considered "mild" or "flagrant" violations of the rules.
The result was that Princeton students saw the Dartmouth team commit twice as many infractions as Dartmouth students professed to see.
Even though students watched the exact same clips, perceptions were vastly different based on their rooting interest. (The students weren't asked to rate how many flagrant fouls Princeton committed.)
It is hardly news that Republicans and Democrats have similarly differing views of the world and, most particularly, the country's highly divisive chief executive.
A new survey by the Pew Research Center, consistent with others, gave President Donald Trump a 39 percent approval rating, with more than half those interviewed, 56 percent, saying they disapproved of the way he was handling the job.
Broken down on partisan lines, the divergence was canyon-sized. The poll found that more than 8 in 10 Republicans approved of Trump's job performance, compared with just 8 percent of Democrats surveyed. Only 35 percent of self-described independents gave Trump positive marks, resulting in his sub-optimal rating.
It should also be no surprise that many of Trump's fellow Republicans have willingly contorted themselves, ignoring or even embracing behavior and policies they would vilify under a Democratic administration, in furtherance _ it is hoped _ of what they consider a greater good.
Juvenile behavior and caustic tweeting is acceptable, by this calculation, so long as Trump nominates sufficiently conservative justices to the Supreme Court. Conflicts of interest and Thursday's antic news conference are fine, if the president signs into law tax cuts and regulatory relief.
Politics under our dominant two-party system is, after all, a team sport, and, like the students of Princeton and Dartmouth, much depends on whether a partisan is wearing a "D" or an "R" jersey.
Democrats have proved similarly pliable.
Many of those who praised President Barack Obama's wielding of executive power as a way around an obstructionist Congress are now horrified by what they see as Trump's attempt to subvert the country's cherished system of checks and balances.
Protesters like damaging or embarrassing leaks targeting the administration and accuse the president and his aides of an Orwellian effort to control information and muzzle dissent. But few spoke up when Obama's Justice Department waged a fight against government whistle-blowers.
What is more striking is how partisan inclinations have come to color perceptions beyond politics.
The University of Michigan, which has been gauging consumer confidence for several decades, found in its February survey a yawning partisan gap that is more typical of political polling.
Shaped by attitudes toward Trump, the study found Democrats' "Expectations Index" _ that is, their outlook on the economy _ was "close to its historic low (indicating recession) and the Republicans' Expectations Index (was) near its historic high (indicating expansion)."
Asked about recent economic news, "30 percent spontaneously mentioned some favorable aspect of Trump's policies, and 29 percent unfavorably referred to Trump's economic policies," the survey's chief economist, Richard Curtin, wrote in summary. "Never before have these spontaneous references to economic policies had such a large impact."
The world is changing by the day.
Anti-communism and suspicion of the Soviet Union _ later Russia _ were bone-deep Republican belief for generations. But when Peter Hart, a political pollster, convened a focus group of Trump voters after the election in Cleveland, he found supporters of the president shared his far more amiable view of America's longtime adversary.
Like Trump, they mostly dismissed evidence of Russian meddling in the 2016 presidential election as a media obsession and excuse for Democrat Hillary Clinton's defeat. Asked to describe Russia's dictatorial president, Vladimir Putin, only three out of a dozen responded with negative depictions. Others praised him as a leader and "badass."
"The sense was, 'If Trump's for it, I'm going to be for it,'" said Hart, a longtime Democratic strategist.
In other words, believing is seeing.
"Rather than voters deciding what they think about abortion or guns or Russia and finding a candidate who fits those views, instead they're settling on a candidate they like for whatever reason and adopting that candidate's political views as their own," said Whit Ayres, a veteran GOP pollster.
"Republicans used to be for free trade and thought free trade was the best way to generate a growing economy. Now Republicans are against free trade because Donald Trump is against free trade," he said.
The inclination to see things a certain, preferred way is not new; the polarity of Dartmouth and Princeton fans showed as much.
But the increasingly adversarial nature of politics, the sorting of America into red and blue sanctuaries, the ability to gorge on self-reinforcing media and never hear a discouraging, or contrary, word seems to have made the phenomenon all the more pronounced.
Neither Hart nor Ayres, who have spent decades sampling voter opinion, see a change anywhere in the offing.
"At the very least, you're going to need a president who makes it his or her mission to try to overcome some of the polarization," Ayres said.
That, of course, assumes he or she could get elected in the first place.
