On his hit HBO television series, “Da Ali G Show,” British Jewish comedian Sacha Baron Cohen is after laughs, but in the process he is creating a new form of sociological experiment.

Each week, under the guise of three different fictitious personas, Baron Cohen is shown interviewing unsuspecting Americans to elicit outrageous and politically incorrect opinions. His signature character is Ali G, a witless, hip-hopping gangster from the London suburbs; Bruno, a gay Austrian fashion maven, is his most flamboyant character. But it is the genial Kazakhstani television journalist Borat Sagdiyev who has proved to be Baron Cohen’s most reliable — and controversial — weapon in working to expose what he sees as America’s hidden underbelly of prejudice and racism.

With Borat, Baron Cohen tests to see if his unwitting guests will embrace or at least acquiesce to the Khazakhi’s warm-spirited xenophobia and antisemitism (they frequently do).

During one recent, particularly loaded interaction, broadcast August 1, Borat led the regulars at the Country West Dancing & Lounge in a sing-along about the troubles back home in his native Kazakhstan. Wearing an awkwardly fitting cowboy hat and smiling eagerly, Borat sang:

In my country there is problem, and that problem is the Jews.They take everybody’s money, they never give it back… . Throw the Jews down the well. Throw the Jews down the well.So my country can be free. So my country can be free.

Judging from the brief video footage of the crowd aired on HBO, audience members appeared to be inspired by the song. They were laughing, stomping their feet and making devil’s horns with their fingers. But interviews with people in the room at the time, as well as of Baron Cohen fans watching the segment at home, suggest that the truth may not be so clear. As it turns out, Baron Cohen’s show tests the limits not only of what ordinary people will say and do, but also of how much we can assume about a person from seeing him or her on television for only a few minutes.

Days after watching the show on HBO, the manager of the Country West, Bill Sandy, still did not appear to grasp that Borat was simply a character, created and portrayed by a comedian from Britain.

“The only thing we were told was that he was from Kaka-kaka-stan or something,” Sandy said. “We don’t know anything about those people.”

Since the show was first broadcast, Sandy said the bar has received numerous calls from neighbors asking excitedly if it was the establishment featured on the HBO program; none voiced concern about the content of the song.

When asked what drove the bar’s patrons to join in singing the anti-Jewish song, Sandy, with his Western twang, replied: “They were just doing what they were told to do.”

A very different picture, though, emerged from a conversation with the treasurer of the company that owns the bar, Carol Pierce, who said that she herself is Jewish. Pierce could be seen during the segment on HBO, laughing heartily behind her goateed husband.

In explaining her light-hearted take on Borat, she pointed out that what television viewers saw was only a few minutes of the two-and-a-half-hour performance that Borat gave when he came to Tucson, Ariz., in April. The rest of Borat’s performance, in which he sang about throwing his wife and family down the well, made it perfectly clear to Pierce that the man performing was a comedian in disguise — who was very funny.

“You could tell by the way they presented him. They brought him in and said he was an up-and-coming country music star,” Pierce recalled. “You could tell right away it was a wig he was wearing, and a fake mustache. I would say 99% of the people in here saw that, too.”

As is the case with all segments on “Da Ali G Show,” viewers were left wondering whether the participants — in this case, the patrons at the bar — were just playing along with the joke or revealing their own bigoted sentiments after being taken in by one of Baron Cohen’s creations.

The mixed responses to this question were evident from one married Jewish couple in New York who watch the show regularly.

Liz Rappaport said the segment was “upsetting,” but not all that revealing. She pointed out that it was impossible to know how Borat set up the song. Her husband, however, had a much more extreme reaction. “It was frightening,” David Rappaport said. “I’m using this as yet another argument for why we need a Jewish homeland.”

For his part, Baron Cohen, a veteran of the Labor Zionist youth group Habonim, does not downplay the sentiments he is stirring up. “Part of the idea of Borat is to get people to feel relaxed enough that they fully open up,” Baron Cohen said in a recent interview with The New York Times. “And they say things that they never would on normal TV. So if they are antisemitic or racist or sexist, they’ll say it.”

Baron Cohen has drawn criticism for confronting sensitive topics in a forum in which winning laughs seems to be the bottom line. The Anti-Defamation League wrote to Baron Cohen one week after the Tucson segment, to tell him of the “hundreds of complaints” they had received.

“While we understand this scene was an attempt to show how easily a group of ordinary people can be encouraged to join in an antisemitic chorus,” the ADL’s national director, Abraham Foxman, wrote in the August 9 letter, “we are concerned that the irony may have been lost on some of your audience — or worse, that some of your viewers may have simply accepted Borat’s statement about Jews at face value.”

Other critics have chastised Baron Cohen for using crude ethnic stereotypes and racial disharmony for laughs.

Baron Cohen is not unaware of the dangers involved in playing with racial politics. When he was studying at Cambridge University, he wrote a thesis on the killing of two Jewish civil-rights activists in Mississippi in 1964. Through his subsequent television work, Baron Cohen has sought to reveal lingering prejudicial attitudes in the South, though he has used humor and misdirection instead of library research.

In one particularly revealing incident, Bruno was shouted off the field of a football game in Alabama, with fans chanting anti-gay slurs, after he began dancing with the cheerleaders. In a more intimate moment, Borat was able to get one white Mississippi wine taster to say that the end of slavery was “good” for blacks, “bad for us.”

Baron Cohen’s interlocutors are not always happy when they see the way they end up being portrayed onscreen. Republican congressional candidate James Broadwater, a Christian conservative running in Mississippi, issued a blistering critique of Baron Cohen on his campaign Web site. In a recent segment, Borat prodded Broadwater into admitting that he thinks all Jews will go to hell if they do not believe in Jesus Christ. After the segment’s broadcast, Broadwater attacked “Da Ali G Show” for its effort to “make Christians look bad and to make me look like a person who hates Jews.” He identified himself as a great friend of Israel, before calling on the Federal Communications Commission to rein in the “liberal, anti-God media.”

For Sandy, any sort of serious reaction to Borat, whether along the lines of Foxman’s or Broadwater’s, misses the point. According to the manager of the Country West Dancing & Lounge, from up close, none of Borat’s antics appear all that weighty: “Everyone took it as just a comedy thing,” Sandy said. “I assume that’s comedy in his country. You’d see if you met the guy.”