True or False? Most American presidents came from humble beginnings.

If you answered true, you're probably in the majority. The "log cabin myth" has been around almost as long as the presidents have, and still persists today.

This homespun bit of American folklore was first used as a political tool on Dec. 11, 1839, according to social historian Edward Pessen. The Baltimore Republican, a newspaper supporting the reelection of President Martin Van Buren, printed this summation of Van Buren's opponent, William Henry Harrison:

"Give him a barrel of hard cider and settle a pension of 2,000 a year on him and he will sit the remainder of his days in his log cabin."

The paper's effort to portray Harrison as an amiable bumpkin, someone who would be satisfied with a little liquor and little else, backfired rather spectacularly.

Harrison's supporters picked up the quote and ran with it. They put out log cabin songbooks and dispensed log cabin cider. Log cabin floats were assembled to dramatize the candidate's alleged humble origins and voters were told that Harrison -- actually born on a plantation to one of the richest families of Virginia -- was from a poor western family.

Harrison was elected, largely as a result of the "log cabin and hard cider" slogans. And his success, Pessen contends, was not lost on later politicians.

"If you convince the American people that your candidate is like them -- that he is of humble circumstances -- you will strike political gold," says Pessen, distinguished professor of history at Baruch College and the Graduate School and University Center of the City University of New York.

"It's a myth that has been widely believed, and the fact that presidents continue to poor-mouth themselves indicates how much it has worked. There's a sort of instinctive conviction that the poorer you were as a kid, the better you'll do as a politician."

The truth, says Pessen: "Only seven of the 39 presidents were Lower Middle Class and below -- but those groups contained roughly 88 percent of the people."

President Reagan, who said at a June '83 news conference that "I was raised in poverty and I remember very well what poverty is," didn't have quite that humble a start, asserts the historian. The Reagan family lived "in attractive rented houses on tree-lined streets in scenic areas."

The elder Reagan was eventually placed in charge of the WPA program in Dixon, Ill. "Government programs to help the poor," says Pessen, "are not normally directed by men themselves poor."

But the greatest contributor to the myth was Lincoln. The 16th president, as every schoolboy learns, was actually born in a log cabin, but this fact, says Pessen, somewhat obscures his true circumstances.

"At the time of his great son's birth, Thomas Lincoln owned two farms of 600 acres, several town lots, livestock, and horses, property that was quite close to the total owned by the wealthiest man in the area," he writes in The Log Cabin Myth (Yale University Press, $16.95). "Five years later he belonged to the richest 15 percent of taxpaying property owners in his community."

Yet in 1860, Lincoln declared that his early life "can all be condensed into a single sentence and that sentence you will find in Gray's Elegy -- 'the short and simple annals of the poor.' "

"Like many men," says Pessen, "Lincoln had come to believe America was a society in which anyone can make it . . . He shared the egalitarian myth."

Lyndon Johnson was another president who liked to assume, in the words of one of his biographers, "the posture of a Horatio Alger figure who rose from rags to riches by hard work, determination, pluck and luck."

But recent biographical evidence, says Pessen, 63, makes it clear that "LBJ was born into an unusually successful family that, it's true, suffered ups and downs . . . For LBJ to depict himself as one more poor American boy, never knowing what comfort was like, is nonsense.

"At almost any point in American history, most people have lived lives so grim, so lacking in opportunity, that what have seemed the humdrum lives of the great majority of American presidents were in fact far more successful than those of an average family."

The log cabin myth is popular among voters, says Pessen, because "it strengthens the attractive self-image that we like to carry about with us, the idea that we are the best nation. In India, for example, Mr. Gandhi steps in as leader because he's the son. 'Not in our country,' we think; 'Here we go after the best.' It's a charming thought, but it's not based on evidence."

Pessen, author of three other books on American political history and editor or coauthor of four more, became interested in the social backgrounds of presidents almost by accident when he was doing "a monstrous study of upward social movement from colonial times to the present. I thought I would write a few paragraphs on the presidents as men who have achieved upward mobility. In other words, I believed in the myth."

Looking for sources to support it, Pessen discovered that the bibliographic cupboard was bare. The "few paragraphs" became the book.

His next project -- interspersed with work on the massive social mobility study -- is on social backgrounds of the top 80 popular American songwriters of the early 20th century.

"Between 80 and 90 percent came from the Upper Middle classes, which contained only 10 to 12 percent of the population. They had advantages -- fathers who were professionals. One suspects that kids born on the wrong side of the tracks might be as good, but their talents might never come to light.

"The successful ones had innate talent, yes, but their families also could afford pianos."