My favorite is Jim Crow, that deeply entrenched set of cultural and institutional practices built up over four centuries of racist domination and exclusion of blacks by whites in the South. Nothing could have been more cultural than that. And yet America was able to dismantle the entire system within a single generation, so much so that today blacks are now making a historic migratory shift back to the South, which they find more congenial than the North. (At the same time, economic inequality, which the policy analysts love to discuss, has hardened in the South, like the rest of America.)

So what are some of the cultural factors that explain the sorry state of young black men? They aren't always obvious. Sociological investigation has found, in fact, that one popular explanation -- that black children who do well are derided by fellow blacks for "acting white" -- turns out to be largely false, except for those attending a minority of mixed-race schools.

An anecdote helps explain why: Several years ago, one of my students went back to her high school to find out why it was that almost all the black girls graduated and went to college whereas nearly all the black boys either failed to graduate or did not go on to college. Distressingly, she found that all the black boys knew the consequences of not graduating and going on to college ("We're not stupid!" they told her indignantly).

SO why were they flunking out? Their candid answer was that what sociologists call the "cool-pose culture" of young black men was simply too gratifying to give up. For these young men, it was almost like a drug, hanging out on the street after school, shopping and dressing sharply, sexual conquests, party drugs, hip-hop music and culture, the fact that almost all the superstar athletes and a great many of the nation's best entertainers were black.

Not only was living this subculture immensely fulfilling, the boys said, it also brought them a great deal of respect from white youths. This also explains the otherwise puzzling finding by social psychologists that young black men and women tend to have the highest levels of self-esteem of all ethnic groups, and that their self-image is independent of how badly they were doing in school.

I call this the Dionysian trap for young black men. The important thing to note about the subculture that ensnares them is that it is not disconnected from the mainstream culture. To the contrary, it has powerful support from some of America's largest corporations. Hip-hop, professional basketball and homeboy fashions are as American as cherry pie. Young white Americans are very much into these things, but selectively; they know when it is time to turn off Fifty Cent and get out the SAT prep book.

For young black men, however, that culture is all there is -- or so they think. Sadly, their complete engagement in this part of the American cultural mainstream, which they created and which feeds their pride and self-respect, is a major factor in their disconnection from the socioeconomic mainstream.