Every current Supreme Court justice attended Harvard or Yale. That's a problem, experts say.

WASHINGTON - It is not hard to see similarities between President Donald Trump's last two Supreme Court nominees: They are both white male conservatives who attended Ivy League law schools, clerked for retiring Justice Anthony M. Kennedy and went to the same exclusive private prep school.

The elite background does not end with them. If the Senate approves Trump's nominee, Brett Kavanaugh, every justice sitting on the Supreme Court will have attended either Yale's or Harvard's law school. (Ruth Bader Ginsburg started at Harvard and transferred to another Ivy, Columbia.)

The shared elite backgrounds of Supreme Court justices, some experts say, is a disadvantage because scientific research shows diverse groups make better decisions.

Groups with vastly diverse members are smarter, more creative, make fewer errors and show increased problem-solving abilities, according to multiple studies across the fields of psychology, business, and organizational and behavioral science.

"The elitism on the Supreme Court is worrying," said Benjamin Barton, a law professor at University of Tennessee at Knoxville. "From the age of 18, these people have all essentially done the same thing, followed the same path, run in the same cloistered circles. That's not healthy."

In 2012, Barton published a comprehensive study on the personal backgrounds of Supreme Court justices. He found that the modern-era court presided over by Chief Justice John G. Roberts Jr. was in many ways the most elitist, homogeneous group assembled since the court's inception.

While the current justices are far more diverse in gender and race than past decades, their educational and work backgrounds are almost uniform.

Almost all studied at the same Ivy League colleges and law schools. Beyond that, Barton's study also found that "the Roberts Court Justices have spent more pre-appointment time in legal academia, appellate judging, and living in Washington, D.C. than any previous Supreme Court."

This cookie-cutter mold is a relatively new phenomenon, experts say.

"One reason you see this happening is because the confirmations have gotten increasingly confrontational," said Richard Davis, a political scientist at Brigham Young University. "It's not like Harvard and Yale are the only good schools out there, but they become stand-ins for merit and a cover for ideology. You see presidents making the argument, 'But look how qualified they are.' The downside to that, unfortunately, is you don't get a diversity of ideas or broader perspectives. You don't get folks who practiced law in Montana or who studied at a school in Illinois."

Recent studies show that homogeneity in teams can have huge impacts, especially in business. A 2015 McKinsey study of 366 public companies found that those with the highest ethnic and racial diversity in management were 35 percent more likely to have better-than-average financial returns. In a different study, when business researchers pitted the abilities of diverse against homogeneous teams in financial markets, the diverse teams were 58 percent more likely to correctly price stocks and avoid overpricing and trader errors.

Last year in Harvard Business Review, two British researchers detailed experiments with cognitive diversity - differences in how individuals respond to new, uncertain and complex situations. Using the same test on teams ranging from a startup biotechnology company to a group of IT consultants, they found correlations between cognitive diversity and better performance. The more diverse teams were better at coming up with different ways of approaching and solving problems.

In another study that sorted 200 participants into racially homogeneous and diverse mock juries, researchers found the diverse juries were forced to cite more facts, deliberated longer and made fewer factual errors in their discussions than all-white mock juries.

"When team members are all the same, you start getting group think," said David Rock, a co-founder of the Neuroleadership Institute who studies neuroscience and leadership. "By contrast, when you have diverse perspectives, people have to work harder to explain themselves and understand each other. They attack problems more robustly and from many more angles. It may feel like harder work and more uncomfortable, but it is in fact more creative and effective."

While the Supreme Court has a long history of Harvard, Yale and other elite pedigrees, its bench has rarely been so dominated by them. Some early justices did not even have formal education. Other justices over the decades have included military veterans, former politicians and former criminal defense lawyers.

In recent years, however, the backgrounds of court nominees have increasingly narrowed to those who have jumped through a series of elite hoops. "It snuck up on us because of how rare these nominations are," Barton said. "But around the Bush and Obama presidencies, people suddenly started noticing that the justices' résumés looked alike."

Barton and others point out the irony that Trump - who rails against "the elite" and the D.C. swamp - has chosen for his nominees two judges with elite pedigree. Last week, as Trump sorted through candidates, one adviser told Washington Post reporters, the president was especially drawn to contenders from Ivy League universities such as Harvard or Yale.

The appeal of an elite background makes sense in many ways.

"What matters is intellectual horsepower, not office-chat charm. It is wisdom and analysis, not personal experiences. If a judge's life is elite in the sense of excellence, that's fine. In fact, that may be the point," then-Berkeley Law dean Christopher Edley Jr. wrote in an essay for The Washington Post in 2010 during Elena Kagan's confirmation process.

An elite background, the popular argument goes, winnows out lesser minds. It is hard to be accepted to Yale Law School, as the current nominee Kavanaugh was. Of those law students, only a handful land clerkships at the Supreme Court. And of those, only a minute few, like Kavanaugh, land federal appellate judgeships.

And yet many studies have shown that teams made up of such star players often perform markedly worse than more diverse groups of randomly selected people.

One of the most frequently cited studies in this vein was conducted in 2004 by two social scientists. They constructed a mathematical model showing that a team made up of the best individual performers can be outperformed by groups of diverse problem solvers because the smart individuals tended to think similarly and would more often get stuck.

Other studies by social psychologists have shown that members of teams with too many "stars" often compete for social standing and have more trouble considering one another's ideas.

There is also something to be said about having more down-to-earth justices who interact with regular citizens, argued Barton, the law professor.

"The Supreme Court justices nowadays all come from academia or federal appellate court. They are as cloistered a group as you can get. They don't rub elbows with anyone except their clerks or lawyers. And the work suffers as a result," he said. "You get these beautiful, super-technical, well-argued-out opinions, but that's not necessarily the same thing as wisdom."

Barton cites writings that range from ancient philosophers such as Aristotle to present-day legal scholars such as former Yale Law School dean Anthony Kronman.

"If you look at their idea of practical wisdom, it comes from life experience," he said. "And that to me is the ultimate argument for why we need diversity. You want people dealing with these huge dilemmas in society to come at it from genuinely different perspectives."