In his latest song, Stevie Wonder asks sarcastically, "Have you heard any good ethnic jokes today?" Wonder finds such humor distasteful, but even he recognizes that during hard times good taste takes a back seat to the perverse pleasure of picking on another, presumably less fortunate, ethnic group.

Now comes William Helmreich, a professor of sociology at the City University of New York, with a book laced with ethnic jokes. The book is worth it just for them. The fact is, and Helmreich never has to come right out and say so, some of the stuff is pretty funny.

And everybody knows that behind closed doors -- in this case, behind your back -- everybody, not just Earl Butz, tells ethnic jokes. Indeed, the best ethnic joke tellers of all time may well be those who are picked on the most -- blacks, Jews, Poles and Japanese. Do we know something you don't?

In "The Things They Say Behind Your Back," Helmreich sets out to tell us what that something is. In a nutshell, it's about the stereotype behind the joke, which is always highly inaccurate, but more often than not contains a kernel of truth. And, as jokes go, it is the distortions of truth that make them funny.

That stereotypes can be quite offensive is not taken lightly by Helmreich. Indeed, he even cautions that a lot of people are going to be angered by the jokes he uses as anecdotes to support the 400 studies on ethnic stereotypes that form the basis of his book.

Who is going to laugh, for example, when reading about the Polish pope who got a new pair of slippers with gold initials inside that said "TGIF," meaning "Toes Go in First"?

Helmreich contends that the time has come for such behind-the-back comics to come out of the closet and be dealt with seriously. For the most part, his attempts at humor serve as attention grabbers when a historical and sociological context for a joke is explored.

"Why do we often stereotype people, even when deep down we know better than that?" Helmreich asks. He does an admirable job of attempting an answer.

Helmreich writes, "Among the most common explanations is that stereotypes are simply a very efficient way of coping with our environment, an environment so complex that we have to break it down into categories before we can understand it . . . Thus stereotypes are convenient, though often inaccurate. Frequently they eliminate the need to learn about people for those who simply do not, either because of fear or sheer laziness, wish to make the effort."

"Most cultures encourage prejudiced attitudes toward other groups," Helmreich says. "These attitudes are ingrained in people beginning with early childhood and are therefore very difficult to overcome."

He cites a study in which a group of whites was shown a photograph of a white person holding a razor blade while arguing with a black person in a New York City subway. They were shown the photo for a split second and then asked to write down what they saw on a slip of paper.

"More than half of the respondents said they saw a black man holding a razor blade against the throat of a white man," Helmreich reports.

Helmreich also notes that not all stereotypes are negative. Indeed, such stereotypes as "Italians are very family oriented" and "the French are great lovers" are promoted by those very groups.

In his book Helmreich explores the myths and historical roots of stereotypes pertaining to nine ethnic groups: Jews, Italians, blacks, Japanese, Chinese, Irish, Poles, WASPs and Hispanics.

In the section on blacks, Helmreich writes, "No group in American society has suffered as much from discrimination as Afro-Americans. The fact is reflected in the paucity of positive stereotypes about them." In that section, stereotypes of hypersensitivity, sexual and athletic prowess and criminality are explored.

Despite his intentions, this treatment is sure to offend more than a few blacks, especially when compared with the stereotypes of the "shrewd businessman Jew," the "competitive Japanese" and even the "cold and insensitive WASP."

However, Helmreich's book is a bold effort at cleaning up a dirty word -- stereotype. And given the tensions in this so-called melting pot of a country, it is a welcome attempt at mutual understanding.