Larry Harrison watches with alarm as noisy Brazilians invade his peaceful island community of Martha's Vineyard in Massachusetts, creating mistrust between old and new residents.
"We are in the United States, not Brazil," the college professor recently shouted at a group of immigrants who he said were among a new crowd who blasted loud music "whenever and wherever."
"They come from a culture that is inconsiderate of others — captured in the Spanish expression Que viva yo or 'Long live I,'" said Harrison, director of the Cultural Change Institute at the Fletcher School at Tufts University.
"It's a human nature problem," he said. "We are not comfortable with people who look, act and speak differently. It contributes to loss of social capital."
The term "social capital" was popularized in 2000 by Harvard University sociologist Robert Putnam, whose best-selling book "Bowling Alone: The Collapse and Revival of American Community" noted a drop in the social networks that allow civic engagement to thrive.
But in another study, Putnam found that as the diversity within a community rises, the number of people in that community who vote, volunteer or give to charity falls.
The politically incorrect findings have been used as ammunition in the ratcheted-up immigration debate.
Several conservative groups have taken a "told-you-so" stance and jumped on his research to seal their own arguments against diversity.
The notion that immigration strengthens society has been the backbone of the American psyche since the term "melting pot" was coined at the turn of the 19th century.
After civil rights legislation in the 1960s, racial diversity was considered irrefutably good for America.
On the face of it, Putnam's study turns that notion on its head.
"There are big payoffs with immigration, but in the short run our research does show none of us is comfortable with diversity, and we all hunker down like a turtle," Putnam told ABCNEWS.com.
In 2000, Putnam interviewed 30,000 people from 41 communities — small and large, rich and poor. Residents were sorted among black, white, Hispanic and Asian. They were asked how much they trusted their neighbors and questioned about civic attitudes, practices and friendships.
The anti-immigration commotion began in June, when it was published by the Scandinavian Public Studies journal after Putnam received a prize for his work.
"Putnam's implications are ominous," wrote conservative blogger Pat Buchanan. "We are talking here about nothing less than the survival of our country."
"If he's right, heavy immigration will inflict social deterioration for decades to come, harming immigrants as well as the native-born," wrote John Leo, editor of the conservative Manhattan Institute's online magazine.
Ex-KKK Wizard Cites Study
Even David Duke, the self-described "white nationalist" and former grand wizard of the Ku Klux Klan, cites Putnam's research on his Web site.
"I've taken a ton of flak," said Putnam, who even received a letter addressed, "Dear intellectual turd."
Putnam was accused of suppressing the study because it contradicted his liberal leanings, even though Harvard released his findings in 2001, and raw data was made publicly available.
"It's wrong to say we hid the data," said Putnam. "We shouted it from the rooftops."
Putnam set out not to study race, but to measure the levels of "social capital" and to go back and remeasure after community leaders enacted changes to see whether "the needle moved."
The most trusting places were "white places" like Duluth, Minn., the state of New Hampshire and Lewiston, Maine, according to Putnam.
Those at the lowest end of the spectrum were cities with large immigrant populations — Los Angeles, Atlanta, Houston and Phoenix.
"We were surprised," said Putnam, who thinks his critics have missed the point.
"The most successful immigrant societies like ours manage that problem over time by assimilating newcomers and creating a more encompassing sense of who we are," said Putnam.
Putnam said that immigration has strengthened the nation culturally and intellectually, but critics only concentrate on the border, "how high the wall should be and the numbers."
"These are legitimate questions, but we are not talking about how to reweave the fabric of our communities," he said.
Putnam's research doesn't "seal the argument" for less diversity, Clarence Page, Pulitzer Prize-winning columnist for the Chicago Tribune, told ABCNEWS.com.
"The reaction is predictable," said Page. "He's raised some interesting points that need to be looked at."
"The American experiment has been a remarkable success, perhaps more than we ever deserved," said Page. "Diversity is enriching, but at the same time, it means that people have a tougher time identifying with each other."
For 12 years, Philadelphia political scientist Harris Sokoloff has worked on the Great Expectations Project, encouraging civic engagement around mayoral elections.
"The greater diversity in the room, the more difficult it is to talk about issues together," according to Sokoloff, associate professor at the University of Pennsylvania's Graduate School of Education.
"We don't have a lot of experience talking to people who are not like ourselves," he said. "It's challenging and we're not practiced at it."
Share, Then Talk
Sokoloff usually facilitates discussions by asking people to "tell stories about themselves. Once we find something we share, then we talk."
Putnam said that the part of his study that was largely ignored was the need to create a "group identity that for a moment trumps the racial identity."
"When you release a study, you lose control of it and it can be used by others in a way that can sometimes inaccurately present your findings," said Margaret Simms, a senior fellow at the Urban Institute, a nonpartisan economic and social policy research organization.
In her research on community engagement in California a decade ago, she found diverse groups were less likely to respond to "artificial interaction" like special festivals and more likely to unify on real issues like crime and schools.
Putnam's research also emphasized how the push-and-pull of ethnic differences strengthen market forces with increased productivity and creativity.
Peter Cappelli, director of the Center for Human Resources at The Wharton School at the University of Pennsylvania, has seen the power of diversity in industry.
"It is a bigger deal now and more of a plus," he said. "Most companies are under pressure to look like the customers they are serving — and most customers are not white guys."
Organizations can create a "powerful sense of identity," said Cappelli, citing cruise ships as an example of where diverse religious and ethnic groups get along.
Historically, Americans know that creating a group identity helps bridge the ethnic divide, according to Putnam. The introduction of the Pledge of Allegiance in classrooms at the turn of the century helped immigrants identify as Americans.
But, warns Larry Harrison, author of "The Central Liberal Truth: How Politics Can Change a Culture and Save It From Itself," today's immigrants need to assimilate better.
'Kibosh on Salad Bowl'
"We've got to emphasize the melting pot and put the kibosh on salad bowl," according to Harrison. "They need to become American."
He urges a crackdown on illegal immigration and a "calibration of the flow" of legal immigrants.
But, concedes Harrison, who has made some headway in getting his Brazilian neighbors to turn down their loud radios, "the issue of trust is complicated."
"I imagine that some WASP [white Anglo-Saxon Protestant] citizens reacted similarly to my grandparents, whom they may have regarded as 'loud Jews.'"
Putnam might agree.
"We have national amnesia on how complicated it was," he said of the early tides of immigration.
"Part of my story is meant to say to my fellow progressives, don't sneer at people who are discombobulated by diversity," he said. "It's real and we cannot let our political correctness get in the way of this serious issue. But we've dealt with this before."