IN his book The Tongue-Tied American, Paul Simon (D.-III.) recounts the answer of a Japanese businessman when asked which is the most important foreign language.

The businessman replied, "Sir, the most useful international language in world trade...is the language of your client."

Imagine an American businessman, tourist or college student asked the same question.

There is something very wrong with the American attitude towards learning a foreign language. The days are past when we could expect English to be spoken everywhere. As America's economic and cultural domination of the world declines, it is imperative that our nation end its ethnocentricism and make an effort to learn about other countries.

The idea that English is the only language worth knowing is not only an insult to the countries with whom we practice trade and tourism, but it is also a handicap to our own success and culture.

Examples of American ineptitude in dealings with foreign countries are many. Gerald Unks, in an article titled, "The Perils of Our Single-Language Policy," tells the story of a General Motors attempt at marketing the Chevy Nova in South America. The company was unaware that "No va" in Spanish means "It doesn't go." Needless to say, the Nova failed to make a big hit.

Another of Unks' examples is Pepsi-Cola's advertising campaign in Taiwan. The slogan "Come Alive with Pepsi," was mistranslated into Chinese as "Pepsi brings your ancestors back from the dead." Another ignorant American marketing move bit the dust.

However humorous these screw-ups may be, they are only an indication of America's enormous lack of interest in learning about its world neighbors.

And the constant question "Don't you speak English?" in the streets and shops of major European cities is nothing short of an embarrassment.

Even for those who will never travel abroad or become international salesmen, learning a foreign language is a valuable experience. A knowledge of the culture of other countries deepens one's understanding of international issues. Those who have an insight into other cultures will have a broader perspective on America and its ties with other countries.

WE must strengthen our effort to learn foreign languages. This must begin in our schools.

In most European nations, students begin learning one foreign language at age 11, and often add a second three or four years later. In the United States, 1985 statistics show, only 15 percent of high school students study any foreign language at all, and less than 4 percent of high school graduates have had more than two years of a foreign language.

In 1966, 34 percent of American colleges required foreign language credit for admission. In 1985, this figure stood at 8 percent.

Harvard, like most schools, holds a disappointing attitude toward foreign languages. Although entering students must fulfill a language requirement during their first year, this requirement is surprisingly weak.

Freshmen must demonstrate proficiency in a language by passing either a CEEB Achievement Test, a Harvard placement test, or an Advanced Placement Examination. Those who don't pass take a full year of foreign language.

While the latter two of these requirements are effective measures of true proficiency, the first two are not. Neither tests the student's ability to speak the language, and a large number of Harvard students meet the requirement without being able to carry on a conversation with a native speaker.

Harvard should test not only for reading and writing proficiency in a foreign language, but also for speaking ability. Neither the College nor the students benefit from the policy of granting diplomas to students who are left speechless in conversation in a foreign country.

For those students who cannot demonstrate speaking proficiency, Harvard should require a one-semester course in culture and conversation. The resources are here; if students would take advantage of them, Harvard could lead the nation to a higher standard of language awareness.